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Plasmon-enhanced photocatalysis provides opportunities for controlling chemical reaction rates, especially when the influence of the light is to enhance or alter charge transfer properties. Semiconductor photocatalysts with an inverse opal or photonic crystal structure not only provide large, open and accessible surface area, they are electrically interconnected as a porous network. This becomes a useful scaffold to dock metallic nanoparticles whose size can be tuned to absorb specific frequencies resonant with their localised surface plasmon resonance. Coupling this with the nature of the metal-semiconductor band structure (where the metal oxide is wide band gap) and exploiting certain properties of photonic crystals, more efficient photocatalysts are possible. We demonstrate semiconducting photonic crystal plasmonic photocatalysts using V2O5 and TiO2 as visible light semiconductor catalysts that showed superior performance to a conventional TiO2 support for hydrogenation of 4-nitrophenol. The approach married the photonic band gap, metal oxide semiconductor bandgap, slow photon effect and localised surface plasmon polaritons to maximum photon absorption to modulate charge transfer and electron density either in the metal nanoparticle, or the conduction band of the semiconductor to give a better photocatalyst. References [1] S. Linic, U. Aslam, C. Boerigter, M. Morabito, Nat. Mater. 14, 567 (2015) [2] S. Linic, P. Christopher, D. B. Ingram, Nat. Mater. 10, 911 (2011) [3] G. Collins, A. Lonergan, D. McNulty, C. Glynn, D. Buckley, C. Hu, and C. O’Dwyer, Adv. Mater. Interfaces. 7, 1901805 (2020). [4] E. Armstrong, C. O’Dwyer, J. Mater. Chem. C 3, 6109 (2015) [5] C. O’Dwyer, Adv. Mater. 28, 5681 (2016) [6] T. Baba, Nat. Photon. 2, 465 (2008) [7] G. Collins, E. Armstrong, D. McNulty, S. O’Hanlon, H. Geaney, C. O’Dwyer, Sci. Technol. Adv. Mater. 17, 563 (2016) [8] A. Lonergan, D. McNulty, C. O’Dwyer, J. Appl. Phys. 124, 095106 (2018) [9] G. Collins, M. Blomker, M. Osaik, J. D. Holmes, M. Bredol, C. O’Dwyer, Chem. Mater. 25, 4312 (2013) [10] J. Liu, H. Zhao, M. Wu, B. Van der Schueren, Y. Li, O. Deparis, J. H. Ye, G. A. Ozin, T. Hasan, B. L. Su, Adv. Mater. 29, 1605349 (2017) [11] S. O’Hanlon, D. McNulty, C. O’Dwyer, J. Electrochem. Soc. 164, D111 (2017) [12] D. McNulty, E. Carroll, C. O’Dwyer, Adv. Energy Mater. 7, 1602291 (2017) Figure 1. V2O5 3D macroporous inverse opal photonic crystal decorated with Au nanoparticles. Figure 1

Zinc oxide (ZnO) and Al-doped ZnO are important optoelectronic materials. ZnO in particular has a wide band gap (Eg ~ 3.3 eV at 300 K), large exciton binding energy (~66 meV) and especially for the variety of methods by which it can be processed. Moreover, ZnO is readily able to alloy with other metals in the oxide form and has a lattice that can facilitate interstitial doping using several metals, including Al and Sn. This gives ZnO a key role in optoelectronics, metal oxide thin films and thin film transistor (TFT) technologies. We demonstrate that crystalline, epitaxial-like and highly ordered ZnO and Al:ZnO (AZO) quasisuperlattice thin films can be achieved from a precursor liquid at relatively low temperature via spin-coating, which crystallize with near epitaxy with a pronounced c-plane texture. We also show the visible and near-infra red (VIS-NIR) light spectroscopy of ZnO and Al:ZnO multi-layered thin film structures grown on oxidized silicon substrates. We show measurements demonstrating sub-band optical pumping of AZO QSLs that enable significant photoconductivity. In AZO QSLs, conduction band electrons from valence band pumping at incident irradiation > Eg, are not required to initiate or enhance photoconductivity, and PL data indicate a donor level that enable enhance sub-band photoconductivity even up to bias voltages of 200 V. Photoexcitation with a 532 nm source efficiently pumps the AZO conduction band without increasing the density of electron-holes in the valence band, minimizing field-driven recombination and enabling significant photoconductance over wide voltage ranges. Density functional theory analysis on ZnO systems with Al-doping configurations of ~2% indicate that interstitial doping is required to generate a density of states that corroborates the proposed donor level to enable the photoconductive properties seen in this work. References [1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano and H. Hosono, Nature 432, 488 (2004). [2] T. Kamiya, K. Nomura and H. Hosono, Sci. Tech. Adv. Mater. 11, 044305 (2010). [3] R. A. Street, Adv. Mater. 21, 2007 (2009). [4] H. Lingling, H. Dedong, C. Zhuofa, C. Yingying, W. Jing, Z. Nannan, D. Junchen, Z. Feilong, L. Lifeng, Z. Shengdong, Z. Xing and W. Yi, Jpn. J. Appl. Phys 54, 04DJ07 (2015). [5] C. Glynn and C. O'Dwyer, Adv. Mater. Interfaces 4, 1600610 (2017). [6] D. Buckley, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, J. Vac. Sci. Technol. A, 35, 061517 (2017). [7] D. Buckley, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, ECS Trans., 77, 99 (2017). [8] D. Buckley, R. McCormack and C. O'Dwyer, J. Phys. D: Appl. Phys., 50, 16TL01 (2017). [9] D. Buckley, R. McCormack, D. McNulty, V. Z. Zubialevich, P. J. Parbrook and C. O'Dwyer, ECS Trans., 77, 75 (2017).

The identification of sulfur host materials, which can overcome issues associated with the insulating nature of sulfur and the shuttling of soluble lithium polysulfides, is crucial in order to realize the practical applications of lithium–sulfur (Li–S) batteries. Therefore, the development of conductive electrode architectures with novel, porous structures is essential to improve the electrochemical performance of Li–S cells. To this end, carbon inverse opals (IOs) were prepared using sacrificial polystyrene spheres, directly on a current-collecting substrate, and were infilled with sulfur via a solution infiltration method. The electrochemical performance of S-infilled carbon IOs (S-CIO), prepared with spheres of different diameters, is evaluated through cyclic voltammetry and galvanostatic cycling. We demonstrate that S-CIO provide long cycle life and stable specific charge, when tested as cathode materials for Li–S batteries. IO samples, prepared with smaller spheres (100 and 200 nm diameters), achieve significantly higher specific charge values than samples prepared with larger spheres. The electrochemical performance of our S-CIO is compared with conventional slurry electrodes containing CIO powder. Mechanical stress during slurry preparation, grinding or ball-milling of material, destroys the IO structure, resulting in worse electrochemical performance as compared to as deposited IO samples. Consequently, this report offers insight into the importance of retaining and optimizing the structure of conductive S-hosts for improving electrochemical performance of Li–S cells.

We report for the first time the self-catalyzed, single-step growth of branched GeSn nanostructures by a vapor–liquid–solid mechanism. These typical GeSn nanostructures consist of ⟨111⟩-oriented, Sn-rich (∼8 atom %) GeSn “branches” grown epitaxially on GeSn “trunks”, with a Sn content of ∼4 atom %. The trunks were seeded from Au0.80Ag0.20 nanoparticles followed by the catalytic growth of secondary branches (diameter ∼ 50 nm) from the excess of Sn on the sidewalls of the trunks, as determined by high-resolution electron microscopy and energy-dispersive X-ray analysis. The nanowires, with ⟨111⟩-directed GeSn branches oriented at ∼70° to the trunks, have no apparent defects or change in crystal structure at the trunk–branch interface; structural quality is retained at the interface with epitaxial crystallographic relation. The electrochemical performance of these highly ordered GeSn nanostructures was explored as a potential anode material for Li-ion batteries, due to their high surface-to-volume ratio and increased charge carrier pathways. The unique structure of the branched nanowires led to high specific capacities comparable to, or greater than, those of conventional Ge nanowire anode materials and Ge1–xSnx nanocrystals.

Germanium (Ge) nanowires were fabricated directly on stainless steel current collectors for Li-ion batteries without any additional catalytic seeds. Substrates of stainless steel are unconventional materials for the direct growth of nanowires for battery applications. Stainless steel substrates were activated for nanowire growth by annealing them in air at a temperature of 450 °C to form a catalytic iron oxide surface layer. Large yields of Ge nanowires were obtained from oxidized stainless steel via a liquid injection chemical vapor deposition process, with diphenylgermane (DPG) as a Ge precursor. Fabricated Ge nanowires have uniform morphology and are single-crystalline. The capacity retention from a nanowire anode tested at 0.2 C is very stable, highlighted by reversible capacities of ∼1014 and 894 mAh/g after the 50th and 250th cycles, respectively. The large specific capacity values are one of the highest achieved for binder-free Ge nanomaterial-based anode materials. The high specific capacity values, good capacity retention, and voltage stability observed resulted from the excellent adhesion of the nanowires to the stainless steel current collectors, ensuring good electrical contact and electrical conductivity. Achieving such electrochemical performance from Ge nanowires grown via a significantly simplified direct growth process on a functional conductive substrate demonstrates the potential of directly grown Ge nanowires as a high-performing anode material for Li-ion batteries., {"references":["https://pubs.acs.org/doi/10.1021/acsaem.0c01977"]}

Adding porosity to battery electrodes is sometimes useful for accommodating volumetric expansion, electrolyte access to active materials, or mitigating poor high-rate performance for thicker electrodes. Ordered macroporous electrode such as inverse opals, are a good model system: binder and conductive additive-free, interconnected electrically, have defined porosity consistent with thickness, good electrolyte wettability and surprisingly good behavior in half-cells and some Li-battery cells at normal rates. We show that at high charge and discharge rates, charge storage in macroporous electrode materials can be completely supressed, and then entirely recovered at low rates. Using a model system of inverse opal V2O5 in a flooded Li-battery three-electrode cell electrodes store almost no charge at rates >10 C, but capacity completely recovers when the rate is reduced to

Carbon inverse opals (IOs) were prepared via a facile synthesis approach using a sucrose-based precursor and polystyrene (PS) spheres as a sacrificial template. During IO preparation, polymer spheres are typically removed by dispersion in organic solvents, such as toluene or tetrahydrofuran. In this study, carbon IOs are prepared with and without removal of PS spheres by toluene to determine the influence of template removal prior to high-temperature treatment on the morphology and chemistry of the resulting carbons. Properties of samples are compared through a systematic investigation by electron microscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. We demonstrate that a commonly used processing step—polymer sphere template chemical removal—does not make any significant difference to the IO morphology. A correlation of Raman spectroscopy with SEM imaging and TGA analysis indicates that carbon IOs prepared without the solvent-treatment step are more ordered than samples prepared with this processing step. The key finding of this report is the simplified IO synthesis procedure, which can be adapted to the preparation of IOs of other materials besides carbon.

The combination of two active Li-ion materials (Ge and Sn) can result in improved conduction paths and higher capacity retention. Here we report; for the first time; the implementation of Ge1-xSnx alloy nanowires as anode materials for Li-ion batteries. Ge1-xSnx alloy nanowires have been successfully grown via vapor-liquid-solid (VLS) technique directly on stainless steel current collectors. Ge1-xSnx (x = 0.048) nanowires were predominantly seeded from the Au0.80Ag0.20 catalysts with negligible amount of growth was also directly catalysed from stainless steel substrate. The electrochemical performance of the the Ge1-xSnx nanowires as an anode material for Li-ion batteries was investigated via galvanostatic cycling and detailed analysis of differential capacity plots. The nanowire electrodes demonstrated an exceptional capacity retention of 93.4 % from the 2nd to the 100th charge at a C/5 rate, while maintaining a specific capacity value of ~921 mAh/g after 100 cycles. Voltage profiles and differential capacity plots revealed that the Ge1-xSnx nanowires behave as an alloying mode anode material, as reduction/oxidation peaks for both Ge and Sn were observed, however it is clear that the reversible lithiation of Ge is responsible for the majority of the charge stored.

The supercapattery is an ideal energy storage device that combines excellent power density and rate capability of supercapacitors and the greater energy density of batteries. With superior storage capacity and long life, this device can be employed in next-generation artificial cardiac pacemakers as a rechargeable energy source for the lifetime of the pacemaker (at least 15-20 years). However, current hybrid energy storage devices are often limited by less than ideal performance of either the supercapacitor or battery. Here, we develop a low cost and scalable prototype supercapattery with cobalt phosphate as positive and activated carbon as negative electrodes. This positive electrode exhibits a maximum specific capacity of 215.6 mAh g-1 (≈1990 F g-1), ever reported in a metal phosphate based electrode. The supercapattery delivers a high energy density of 3.53 mWh cm-3 (43.2 Wh kg-1) and a power density of 425 mW cm-3 (5.8 kW kg-1). Furthermore, the device can retain 79% voltage even after 4 minutes self-discharge, enough to provide power during cardiac emergencies. This hybrid device provide excellent performance and stability under physiological temperature range (35-41 °C), retaining 68% of specific capacity after 100,000 cycles at room temperature (25 °C) and up to 81.5% after 20,000 cycles at 38 °C, demonstrating its effectiveness as a potential power source for the next-generation implanted medical devices.

In Li-S batteries, it is important to ensure efficient reversible conversion of sulfur to lithium polysulfide (LiPS). Shuttling effects caused by LiPS dissolution can lead to reduced performance and cycle life. Although carbon materials rely on physical trapping of polysulfides, polar oxide surfaces can chemically bind LiPS to improve the stability of sulfur cathodes. We show a simple synthetic method that allows high sulfur loading into mesoporous carbon preloaded with spatially localized nanoparticles of several Magneli-phase titanium oxide (Tin O2n-1 ). This material simultaneously suppresses polysulfide shuttling phenomena by chemically binding Li polysulfides onto several Magneli-phase surfaces in a single cathode and ensures physical confinement of sulfur and LiPS. The synergy between chemical immobilization of significant quantities of LiPS at the surface of several Tin O2n-1 phases and physical entrapment results in coulombically efficient high-rate cathodes with long cycle life and high capacity. These cathodes function efficiently at low electrolyte-to-sulfur ratios to provide high gravimetric and volumetric capacities in comparison with their highly porous carbon counterparts. Assembled coin cells have an initial discharge capacity of 1100 mAh g-1 at 0.1C and maintain a reversible capacity of 520 mAh g-1 at 0.2C for more than 500 cycles. Even at 1C, the cell loses only 0.06 % per cycle for 1000 cycles with a coulombic efficiency close to 99 %.

This work reports an enzyme-less glutamate sensor based on nickel oxide modified glassy carbon electrode. The nanoparticles of NiO were synthesized by sol–gel method, and showed high electro-catalytic activity towards glutamate oxidation in 0.1 M NaOH solution. The sensor displays a fast response time of

For oxides, especially as lithium-ion battery anodes, it is important to engineer the material not only to improve the kinetics of reversible lithiation efficiency, but to avoid capacity and voltage fading, and side reactions from conversion mode processes that can sometimes occur in tandem with intercalation. We report the first electrochemical evaluation of NiVO3 as an intercalation anode material for Li-ion batteries, which offers a high capacity with negligible fading without conversion mode side reactions. Binary metal oxide NiVO3 fused oxide nanoparticles (Ni–FONPs) are formed via thermal reduction of Ni-doped vanadium oxide nanotubes (Ni-VONTs). The electrochemical performance of Ni–FONPs is contrasted with that of a composite of Fe2O3 and V2O3 (Fe–FONPs) with a similar morphology, synthesized using a similar process from Fe-doped VONTs. Galvanostatic cycling reveals that the binary metal oxide Ni–FONPs exhibit superior electrochemical performance compared to the Fe–FONPs by avoiding segregation into two oxides, one of which ordinarily cycles as a conversion mode material. The new anode material, Ni–FONPs, demonstrates state-of-the-art specific capacity retention (78% from the 2nd to the 500th cycle) and significantly long cycle life (500 cycles) when cycled using a specific current of 200 mA g−1 in a conductive additive and binder-free formulation. Limiting the lower voltage to ∼0.2 V avoids separate oxides of Ni and V, which independently, are detrimental to cycle life and capacity retention. Systematic analysis of differential capacity obtained from galvanostatic voltage profiles over 500 cycles offers a detailed insight into the charge storage mechanism and electrochemical behaviour of this stable NiVO3 anode material.

We demonstrate that crystalline macroporous GeO2 inverse opals exhibit state-of-the-art capacity retention, voltage stability and a very long cycle life when tested as anode materials for Li-ion batteries. The specific capacities and capacity retention obtained from GeO2 IOs are greater than values reported for other GeO2 nanostructures and comparable to pure Ge nanostructures. Unlike pure Ge nanostructures, GeO2 IOs can be prepared in air without complex processing procedures, potentially making them far more attractive from an industrial point of view, in terms of cost and ease of production. Inverse opals are structurally and electrically interconnected, and remove the need for additives and binders. GeO2 IOs show gradual capacity fading over 250 and 1000 cycles, when cycled at specific currents of 150 and 300 mA/g, respectively, while maintaining high capacities and a stable overall cell voltage. The specific capacities after the 500th and 1000th cycles at a specific current of 300 mA/g were ~ 632 and 521 mA h/g respectively, corresponding to a capacity retention in each case of ~ 76% and 63% from the 2nd cycle. Systematic analysis of differential capacity plots obtained from galvanostatic voltage profiles over 1000 cycles offers a detailed insight into the mechanism of charge storage in GeO2 anodes over their long cycle life. Rate capability testing and asymmetric galvanostatic testing demonstrate the ability of GeO2 IO samples to deliver significantly high capacities even at high specific currents (1 A/g).

Nickel Phosphate (Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]•12H2O) – VSB-5 nano/micro rods composite with reduced graphene oxide (rGO) was successfully synthesized using a Polyvinyl Pyrrolidone (PVP) aided hydrothermal technique and applied as a battery-type cathode for supercapatteries. The uniform meso/microporous structure provides more electro-active sites for surface redox reaction and nano-paths for electrolyte ion diffusion which can significantly improve the device performance. From the electrochemical analysis, it was found that VSB-5/rGO exhibited a specific capacity of 117.3 mAh g−1 (1056.1 F g−1) which was noticeably higher than the pristine VSB-5 (60.7 mAh g−1) at 5 mA cm−2. These excellent electrochemical performances may be due to rGO modification and well-defined nano/micro rods. Furthermore, supercapatteries were fabricated by pairing a commercially available activated carbon (AC) electrode with VSB-5/rGO as a positrode. The fabricated cell was tested and showed a high specific capacity of 86.8 mAh g−1 (208.4 F g−1) with 88% capacity retention after 5000 cycles. Finally, the assembled supercapattery delivered a maximum specific energy of 80.5 Wh kg−1 at a power output of 2216.5 W kg−1. In comparison with a pristine VSB-5 based device, the AC/VSB-5/rGO device shows remarkable electrochemical performance, demonstrating that VSB-5/rGO is a promising, new electrode material for high performance supercapatteries.

We report on the electrochemical performance of V2O3 polycrystalline nanorods (poly-NRs) as a cathode material for Li-ion batteries. Poly-NRs are formed through the thermal treatment of V2O5 nanotubes in a N2 atmosphere. X-ray and electron diffraction techniques are used to confirm the thermal reduction. Through galvanostatic cycling, we demonstrate that poly-NRs offer excellent capacity retention over 750 cycles. The capacity retention from the 50th to the 750th cycle was an impressive 94 %, retaining a capacity of approximately 120 mAh g−1 after 750 cycles. The outstanding stability of the nanocrystal-containing V2O3 poly-NRs over many cycles demonstrates that vanadium(III) oxide (V2O3) performs very well as a cathode material. Full Li-ion cells with paired a V2O3 poly-NR cathode and a pre-charged Co3O4 inverse opal (IO) conversion mode anode demonstrated high initial capacities and retained a capacity of 153 mAh g−1 after 50 cycles. The capacities achieved with our V2O3 poly-NRs/Co3O4 IO full cells are comparable to the capacities obtained from the most commonly used cathode materials when cycled in a half-cell arrangement versus pure Li metal.

Zinc oxide is an important optoelectronic material, of particular interest due to its wide band gap (Eg ~ 3.3 eV at 300 K), large exciton binding energy (~66 meV) and especially for the variety of methods by which it can be processed. Moreover, ZnO is readily able to alloy with other metals in the oxide form and has a lattice that can facilitate interstitial doping. This gives ZnO a key role in the area of optoelectronics, metal oxide thin films and thin film transistor (TFT) technologies. We demonstrate that crystalline, epitaxial-like and highly ordered ZnO thin films can be achieved from a precursor liquid at relatively low temperature via spin-coating. The synthesised films are smooth, stoichiometric ZnO with controllable thickness. An iterative layer-by-layer coating schematic is employed to demonstrate the effects of film thickness on structure, morphology as well as the surface and internal defects. Characterisation of the crystallinity, morphology, O-vacancy formation, stoichiometry, surface roughness and thickness variation was determined through X-ray diffraction, scanning and transmission electron and atomic force microscopy, X-ray photoelectron and photoluminescence spectroscopy, and the data of multi-layered ZnO correlated to defect formation and electrical conductivity. It is imperative that high crystal quality epitaxial-like thin films can be formed from solution processing to compete with physical deposition methods. We demonstrate that iterative spin-coating of deposited ZnO films results in a transition in crystal texture with increasing thickness (number of layers) from the [] m-plane to the [] c-plane. The films attain a c-axis preferential orientation, with no other crystalline peaks present. Results show that the film’s surface morphology was very smooth, with average rms roughness

We report on the electrodeposition of 3D macroporous vanadium oxide inverse opals and binary inverse opals on transparent conducting oxide substrates and stainless steel and thermally oxidized stainless steel substrates. The electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of a colloid photonic crystal template of self-assembled polystyrene spheres. Inverse opals were grown using spheres ranging in diameter from 0.5 μm to 6 μm, and binary inverse opals were also electrodeposited using binary mixtures of sphere sizes. We demonstrate that the ionic diffusion that leads to growth has charge-to-mass Coulombic efficiency ranging from 60–90%, depending on the voltage used. Additionally, the tortuosity in ionic diffusion through the opal to the substrate is significantly increased when large sphere diameter templates and binary opal templates are used. Analysis of the contribution of true substrate active area and the influence of template structure on ionic diffusivity confirms that inverse opal growth is dictated by the size of opal spheres, interstitial void clogging by smaller spheres in binary opals, and the conductivity of the substrate active area. The crystallinity of the inverse opal is consistent and a function of applied voltage, and attains phase pure orthorhombic V2O5.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 23/04/2022 Delivering therapeutics to disease sites is a challenge facing modern medicine. Nanoparticle delivery systems are of considerable interest to overcome this challenge, but these systems suffer from poor clinical translation. It is believed this is, in part, due to incomplete understanding of nanoparticle physico-chemical properties in vivo. To understand how nanoparticle properties could change following intravenous delivery, Au, Ag, Fe2O3, TiO2, and ZnO nanoparticles of 5, 20, and 50 nm were characterised in water and physiological fluids. The effects of the dispersion medium, concentration, and incubation time on size, dispersion, and zeta potential were measured. Properties varied significantly depending on material type, size, and concentration over 24 h. Gold and silver nanoparticles were generally the most stable. Meanwhile, 20 nm nanoparticles appeared to be the least stable size, across materials. These results could have important implications for selecting nanoparticles for drug delivery that will elicit the desired physiological response. ACCEPTED peer-reviewed

Plasmonic photocatalysis has facilitated rapid progress in enhancing photocatalytic efficiency under visible light irradiation. Poor visible-light-responsive photocatalytic materials and low photocatalytic efficiency remain major challenges. Plasmonic metal-semiconductor heterostructures where both the metal and semiconductor are photosensitive are promising for light harvesting catalysis, as both components can absorb solar light. Efficiency of photon capture can be further improved by structuring the catalyst as a photonic crystal. Here we report the synthesis of photonic crystal plasmonic photocatalyst materials using Au nanoparticle-functionalized inverse opal (IO) photonic crystals. A catalyst prepared using a visible light responsive semiconductor (V2O5) displayed over an order of magnitude increase in reaction rate under green light excitation ($\lambda$=532 nm) compared to no illumination. The superior performance of Au-V2O5 IO was attributed to spectral overlap of the electronic band gap, localized surface plasmon resonance and incident light source. Comparing the photocatalytic performance of Au-V2O5 IO with a conventional Au-TiO2 IO catalyst, where the semiconductor band gap is in the UV, revealed that optimal photocatalytic activity is observed under different illumination conditions depending on the nature of the semiconductor. For the Au-TiO2 catalyst, despite coupling of the LSPR and excitation source at $\lambda$=532 nm, this was not as effective in enhancing photocatalytic activity compared to carrying out the reaction under broadband visible light, which is attributed to improved photon adsorption in the visible by the presence of a photonic band gap, and exploiting slow light in the photonic crystal to enhance photon absorption to create this synergistic type of photocatalyst., Comment: 19 pages, 8 figures, + Supporting information

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 03/01/2020 Efficient synthetic protocols for stable oxide materials as Li-ion battery electrodes are important not only for improving long-term battery performance but also for tackling potential material abundance issues and understanding the nature of ion intercalation for beyond lithium technologies. Oxide anodes are denser, typically, than graphite, leading to a doubling or more of the energy density. Using oxides as lower voltage battery anodes that efficiently and reversibly intercalate cations while avoiding dominating conversion-mode side reactions is much less common. We show that ion-exchanging the molecular templates used to form scrolled, layered vanadium oxide nanotubes (VONTs) with sodium ions allows us to form NaV2O5 crystals that behave as Li-ion battery anodes with efficienct capacity retention over 1000 cycles. We also track and analyze the thermal recrystallization of intralayer Na+ ion-exchange in vanadium oxide nanotubes (Na-VONTs) to NaV2O5 by thermogravimetric analysis, X-ray and electron diffraction, transmission and scanning electron microscopy, and infrared spectroscopy. The quantification and understanding of the electrochemical performance of ion-exchanged nanotubes before and after thermal treatment was determined by cyclic voltammetry and galvanostatic cycling. NaV2O5 in the form of micro- and nanoparticles demonstrates exceptional capacity retention during long cycle life galvanostatic cycling with Li+, retaining 93% of its capacity from the 100th to the 1000th cycle, when cycled using an applied specific current of 200 mA/g in a conductive additive and binder-free formulation. Intercalation reactions dominate over much of the voltage range. Conversion mode processes are negligible and the material reversibly lithiates with charge compensation by cation (V) redox. This report offers valuable insight into the use of group I (Li, Na, etc.) elements to make vanadate bronzes as long cycle life and stable Li-ion battery anode materials with higher volumetric energy density.

This talk will summarize recent results of ordered macroporous (inverse opal) materials made from a range of transition metal oxides when used as Li-ion battery electrodes. The basic methodology for macroporous material formation will be presented for electrodes fabricated with macroporous ordered materials included TiO2, SnO2, GeO2, V2O5, their mixtures and other compounds. The talk will compare the basic lithiation response in these porous materials in Li-in battery half cells and detail the electrochemical response of each oxide and porous structure as a function of specific current (rate) and cycle life. Several of these materials offer surprisingly good electrochemical stability during long (>5000 cycles in the case of TiO2) cycle life, in a binder and conductive additive-free electrode formulation. We also summarize limits of some macroporous oxide materials at very high charge and discharge rates when used in Li-ion batteries and compare the influence of phase and structure on reversible lithiation. Related work and References O'Hanon, D. McNulty, R. Tian, J. Coleman, and C. O'Dwyer, High Charge and Discharge Rate Limitations in Ordered Macroporous Li-ion Battery Materials, J. Electrochem. Soc. 167, 140532 (2020). McNulty, H. Geaney, Q. Ramasse, and C. O'Dwyer, Long Cycle Life, Highly Ordered SnO2/GeO2 Nanocomposite Inverse Opal Anode Materials for Li‐Ion Batteries, Adv. Funct. Mater., 2005073 (2020). McNulty, H. Geaney, D. Buckley, and C. O'Dwyer, High Capacity Binder-free Nanocrystalline GeO2 Inverse Opal Anodes for Li-ion Batteries with Long Cycle Life and Stable Cell Voltage, Nano Energy 43, 11 (2018). McNulty, E. Carroll, and C. O'Dwyer, Rutile TiO2 Inverse Opal Anodes for Li-ion Batteries with Long Cycle Life, High-rate Capability and High Structural Stability, Adv. Energy Mater. 7, 1602291 (2017). McNulty, A. Lonergan, S. O'Hanlon, and C. O'Dwyer, 3D open-worked inverse opal TiO2 and GeO2 materials for long life, high capacity Li-ion battery anodes, Solid State Ionics 314, 195 (2018). Lonergan, D. McNulty, and C. O'Dwyer, Tetrahedral framework of inverse opal photonic crystals defines the optical response and photonic band gap, J. Appl. Phys. 124, 095106 (2018). O'Hanlon, D. McNulty, and C. O'Dwyer, The influence of colloidal opal template and substrate type on 3D macroporous single and binary vanadium oxide inverse opal electrodeposition, J. Electrochem. Soc. 164, D111 (2017). O'Dwyer, Colour-Coded Batteries – Inverse Opal Materials Circuitry for Enhanced Electrochemical Energy Storage and Optically Encoded Diagnostics, Adv. Mater. 28, 5681 (2016).

New techniques to directly grow metal oxide nanowire networks without the need for initial nanoparticle seed deposition or postsynthesis nanowire casting will bridge the gap between bottom-up formation and top-down processing for many electronic, photonic, energy storage, and conversion technologies. Whether etched top-down, or grown from catalyst nanoparticles bottom-up, nanowire growth relies on heterogeneous material seeds. Converting surface oxide films, ubiquitous in the microelectronics industry, to nanowires and nanowire networks by the incorporation of extra species through interdiffusion can provide an alternative deposition method. It is shown that solution-processed thin films of oxides can be converted and recrystallized into nanowires and networks of nanowires by solid-state interdiffusion of ionic species from a mechanically contacted donor substrate. NaVO3 nanowire networks on smooth Si/SiO2 and granular fluorine-doped tin oxide surfaces can be formed by low-temperature annealing of a Na diffusion species-containing donor glass to a solution-processed V2 O5 thin film, where recrystallization drives nanowire growth according to the crystal habit of the new oxide phase. This technique illustrates a new method for the direct formation of complex metal oxide nanowires on technologically relevant substrates, from smooth semiconductors, to transparent conducting materials and interdigitated device structures.

Vanadium oxide nanostructures have been widely researched as a cathode material for Li-ion batteries due to their layered structure and shorter Li+ diffusion path lengths, compared to the bulk material. Some oxides exhibit charge storage due to capacitive charge compensation, and many materials with cation insertion regions and rich surface chemistry have complex responses to lithiation. Herein, detailed analysis by cyclic voltammetry was used to distinguish the charge stored due to lithium intercalation processes from extrinsic capacitive effects for micron-scale bulk V2O5 and synthesized nano-scale vanadium oxide polycrystalline nanorods (poly-NRs), designed to exhibit multivalent surface oxidation states. The results demonstrate that at fast scan rates (up to 500 mV/s), the contributions due to diffusion-controlled intercalation processes for micron-scale V2O5 and nanoscale V2O3 are found to dominate irrespective of size and multivalent surface chemistry. At slow potential scan rates, a greater portion of the redox events are capacitive in nature for the polycrystalline nanorods. Low dimensional vanadium oxide structures of V2O5 or V2O3, with greater surface area do not automatically increase their (redox) pseudocapacitive behaviour significantly at any scan rate, even with multivalent surface oxidation states.

The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO3 nanowires (NWs) and their conversion to tunnel structured β-AgVO3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO3 to β-AgVO3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO3 NWs offers insight into the true β-AgVO3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO3 NWs have a core–shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO3 NWs core material. Electrochemical comparison of α-AgVO3 and β-AgVO3 NWs confirms that β-AgVO3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO3 NWs after the first galvanostatic discharge and charge offers new insight into the Li+ reaction mechanism for β-AgVO3. Ag+ between the van der Waals layers of the vanadium oxide is reduced during discharge and deposited as metallic Ag, the vacant sites are then occupied by Li+.

Three-dimensional (3D) hybrid nanostructured electrodes based on one-dimensional (1D) nanorod arrays have recently attracted great attention owing to their synergistic effect of three-dimensional nanostructures and application in energy storage and conversion devices. Here, we designed a heterostructured supercapattery electrode from a combination of NiO and In2O3 with a hierarchical hybrid microstructure on nickel foam (NF). Simultaneous heterogeneous growth of 1D nanorod-supported 3D microflower structures on nickel foam enhanced the non-capacitive faradaic energy storage performance due to the synergistic contribution from hierarchical hybrid nanostructure. The heterostructured electrode exhibits a high specific capacity of 766.65 C g-1 at 5 A g-1 and remains as high as 285.12 C g-1 at 30 A g-1. The composite electrode shows an excellent rate performance as a sandwich type symmetric device, offering a high specific energy of 26.24 W h kg-1 at a high power of 1752.8 W kg-1. The device shows a long term cyclic stability with 79% retention after 50 000 cycles, which is remarkable for an oxide based pseudocapacitor. These results suggest that NiO-In2O3 with hybrid micro/nano architecture could be a promising electrode for next generation supercapatteries.

Cathode materials in Li-ion batteries, especially oxides, are still under intense investigation as electric vehicle and other demanding application require longer cycle life and higher energy density. V2O5 is an important cathode material for Li ion batteries enabling a stable reaction with lithium through a series of phase changes that are Coulombically efficient and reversible. V2O5 can be improved by modifying the physical structure as well as its crystalline structure or stoichiometry. These modifications include macroporous, interconnected networks or the oxide that enhanced stability and mitigate capacity fading under some conditions, as in context we show our recent development with 3DOM battery materials as a comparison to the data presented in this paper. Such improvements are investigated in this work through the development of a unique inverse opal ordered 3D macroporous of V2O5 by electrodeposition. We show the electrodeposition follows a diffusion limited growth mode to form 3D porous crystalline V2O5 after removal of the colloid self-assembled photonic crystal template. Structurally stable electrodeposited vanadium pentoxide inverse opal networks on FTO-coated glass are electrochemically tested as a function of C-Rate, i.e. the inverse of the time (in hours) it takes for the electrode fully discharges or charges (1C = 1/n hours). By selectively controlling whether the inverse opal network is open-worked or overfilled is also of focus in the galvanostatic cycling investigation. Electrochemical analysis shows lithium phase shifts with increasing C-rate in both open and overfilled network cases, which affect specific capacity retention in the electrode. Raman scattering and X-ray diffraction is used to investigate the change in each electrode as a function of C-rate, along with electron microscopy analysis to investigate the effect of C-rate on the structural changes to theV2O5 inverse opal network. Using chronoamperometry, we also show that the nature of the limited response in ordered porous cathodes materials at high rates is governed almost entirely by electronic conductivity, even with advantageous electrolyte access to the material surface. References [1] S. O'Hanlon, D. McNulty, and C. O'Dwyer, J. Electrochem. Soc. 164, D111 (2017). [2] D. McNulty, E. Carroll, and C. O'Dwyer, Adv. Energy Mater. 7, 1602291 (2017). [3] G. Collins, E. Armstrong, D. McNulty, S. O'Hanlon, H. Geaney, and C. O'Dwyer, Sci. Technol. Adv. Mater. 17, 563 (2016). [4] M. Osiak, H. Geaney, E. Armstrong, and C. O'Dwyer, J. Mater. Chem. A 2, 9433 (2014). [5] D. McNulty, A. Lonergan, S. O'Hanlon, and C. O'Dwyer, Solid State Ionics 314, 195 (2018). [6] J. Ye, A. C. Baumgaertel, Y. M. Wang, J. Biener, M.M. Biener, ACS Nano 9, 2194 (2015) [7] K. Lu, J. Xu, J. Zhang, B. Song, H. Ma, ACS Applied Materials & Interfaces 8, 17402 (2016) [8] R. Tian, N. Alcala, S. J. O'Neill, D. Horvath, J. Coelho, A. Griffin, Y. Zhang, V. Nicolosi, C. O'Dwyer, J. N. Coleman, ACS Appl. Energy Mater. 3, 2966 (2020) [9] D. McNulty, H. Geaney, D. Buckley, and C. O'Dwyer, Nano Energy 43, 11 (2018).

New types of transparent conducting materials (TCMs) are being sought due to the increase in demand for their use in next generation electronics and photonics. Methods to improve transparency be inferred by controlling porosity (graded refractive index), or from a change in the crystal structure of some materials that are not inherently transparent at visible frequencies. Transparent materials with tunable optical properties are important in conductive and capacitive displays, tandem solar cells, organic PVs and other devices. Transparent conducting oxides (TCO) have been extensively used in various technologically important applications including solar cells, flat panel displays, antireflective coatings, (organic)light emitting diodes and many other uses as advanced optical materials. Nanoporous and nanostructured films, assemblies and arrangements are important from an applied point of view in microelectronics, photonics and optical materials. The ability to minimize reflection, control light output and use contrast and variation of the refractive index to modify photonic characteristics can provide routes to enhanced photonic crystal devices, omnidirectional reflectors, antireflection coatings and broadband absorbing or reflecting materials. Here, we detail how interdiffusion processes can be used to modify the crystallinity and phase of solution processed semiconducting oxides, to dielectric complex oxides on glass as thin films or as oxide nanowire networks. In addition, we demonstrate how electrodeposition of mobile ionic species on TCOs and SiO2/Si can allow this process to happen from a top down process, enabling patterned optically transparent coatings with in-plane semiconductor-dielectric contrast. Last, we show how these processes can allow networks of oxide nanowire to form directly from solution processed oxide thin films on a range of substrate types. Antireflective properties and the onset of broadband transparency for interdiffusion-mediated oxide conversion processes are also shown. References [1] C. M. Eliason and M. D. Shawkey, Opt. Express, 22, A642 (2014). [2] C. Glynn and C. O'Dwyer, Adv. Mater. Interfaces, 4, 1600610 (2017). [3] C. O’Dwyer, M. Szachowicz, G. Visimberga, V. Lavayen, S. B. Newcomb and C. M. S. Torres, Nature Nanotechology, 4, 239 (2009). [4] J. Q. Xi, M. F. Schubert, J. K. Kim, E. F. Schubert, M. Chen, S. Y. Lin, W. Liu and J. A. Smart, Nature Photonics, 1, 176 (2007). [5] C. O'Dwyer and C. M. S. Torres, Front. Physics, 1, 18 (2013). [6] C. Glynn, D. Creedon, H. Geaney, J. O'Connell, J. D. Holmes and C. O'Dwyer, ACS Appl. Mater. Interfaces, 6, 2031 (2014). [7] K. K. Banger, Y. Yamashita, K. Mori, R. L. Peterson, T. Leedham, J. Rickard and H. Sirringhaus, Nature Materials, 10, 45 (2011). [8] C. Glynn, D. Creedon, H. Geaney, T. Collins, E. Armstrong, M. A. Morris and C. O'Dwyer, Sci. Rep., 5, 11574 (2015). [9] C. Glynn, D. Aureau, G. Collins, S. O'Hanlon, A. Etcheberry and C. O'Dwyer, Nanoscale, 7, 20227 (2015). [10] C. Glynn, H. Geaney, D. McNulty, J. O'Connell, J. D. Holmes and C. O’Dwyer, J. Vac. Sci. Technol. A, 35, 020602 (2017). [11] C. Glynn, L. Balobaid, D. McNulty and C. O’Dwyer, ECS J. Solid State Sci. Technol., 6 N227 (2017).

Conductive and paintable inks of 2D layered MoS2 with aspect ratio-dependent conductivity are demonstrated. Using ultrasonically assisted solvent-exfoliation of MoS2, high concentration 2D and few-layer suspensions become inks that provide coherent films when painted. Conductivity of paintable 2D MoS2 inks can be modulated by length and width, where the conductivity is linked to the painting direction. Reducing the painted film width, increases conductivity for similar length, and the films conductivity is aspect ratio-dependent. Inks of solvent-exfoliated 2D MoS2 can be painted without polymeric additives.

To date lithium-ion (Li-ion) batteries have been the de facto commercial battery type used in consumer electronics as well as in the first generation of electric vehicles (EVs). However, increases in the practical energy density of Li-ion batteries are too sluggish to keep pace with the demands of the next generation of portable electronics and EVs. Lithium Sulfur (Li–S) batteries are one of the most promising “beyond Li-ion” rechargeable battery systems in terms of both cost and specific energy density. (1, 2) Li–S batteries can deliver a practical specific energy density of 600 Wh/kg, which is more than double the values offered by state-of-the-art Li-ion batteries. (3, 4) However, there are still issues, which need to be addressed before widespread commercialization of Li–S batteries can be possible. Sulfur (S) and lithium sulfide (Li2S) have intrinsically low electronic conductivity. (5) Furthermore, the high-order lithium polysulfides (Li2Sx (6 < x ≤ 8)), which are formed upon first lithiation, are highly soluble in the standard liquid Li–S battery electrolyte. These various polysulfide anions are mobile and can be partially reduced and oxidized multiple times in the vicinity of the anode and cathode, respectively, leading to a so-called polysulfide shuttle phenomenon. (6) Additionally, the large volume changes (80%) which are associated with conversion reactions can lead to electrode disintegration and electrical isolation issues, resulting in severe capacity decay. (7) Various methods have been explored in an attempt to tackle these detrimental issues. Sulfur-carbon composites have been investigated to improve conductivity, following the pioneering work of the Nazar Group. (8) Efforts to reduce the polysulfide shuttle have been made via the application of various polysulfide-trapping interlayers, the use of functional separators and the exploitation of solid-state electrolytes. In this work, we detail the preparation of carbon nanospheres (CNS) with application as conductive sulfur host materials for Li–S batteries. CNS are prepared via facile hydrothermal treatment with different cost-effective precursors and the influence of each precursor on the structural and physical properties of the nanospheres is determined through examination of electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy and gas adsorption data. The electrochemical performance of sulfur infilled CNS samples is evaluated through comparison of cyclic voltammetry and galvanostatic cycling data. We demonstrate that the choice of carbon precursor can have a significant influence on the performance of the CNS-based sulfur electrodes. Sulfur infilled CNS materials, which are morphologically similar, can have significantly different electrochemical response due to differences in their physical properties such as pore volume and pore structure. References: 1. A. Manthiram, Y. Fu, S.-H. Chung, C. Zu and Y.-S. Su, Chem. Rev., 114, 11751 (2014). 2. S. Urbonaite and P. Novák, J. Power Sources, 249, 497 (2014). 3. P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 11, 19 (2011). 4. D. Lv, J. Zheng, Q. Li, X. Xie, S. Ferrara, Z. Nie, L. B. Mehdi, N. D. Browning, J.-G. Zhang, G. L. Graff, J. Liu and J. Xiao, Adv. Energy Mater., 5, 1402290 (2015). 5. H. Chu, H. Noh, Y.-J. Kim, S. Yuk, J.-H. Lee, J. Lee, H. Kwack, Y. Kim, D.-K. Yang and H.-T. Kim, Nat. Commun., 10, 188 (2019). 6. Y. V. Mikhaylik and J. R. Akridge, J. Electrochem. Soc., 151, A1969 (2004). 7. F. Jin, S. Xiao, L. Lu and Y. Wang, Nano Lett., 16, 440 (2016). 8. X. Ji, K. T. Lee and L. F. Nazar, Nat. Mater., 8, 500 (2009).

By forming anatase TiO2 inverse opals by infiltration of an opal photonic crystal, we demonstrate that the optical response and angle-resolved blue-shift of the band-gap of the inverse opal structure are defined by a particular three-dimensional structure of the infilled voids. The optical structure of TiO2 inverse opals usually displays significant deviation from its physical structure and from the theoretically predicted position of the photonic band-gap. Following rigorous structural characterization of the parent opal template and TiO2 inverse opals, alternative explanations for the signature of optical transmission through inverse opals are proposed. These approaches posit that, for light-matter interaction, an inverse opal is not precisely the inverse of an opal. Accurate parameters for the structure and material properties can be obtained by invoking a Bragg FCC selection rule-forbidden (-211) plane, which is not a realistic model for diffraction in the IO. Alternatively, by assuming optical interactions with just the periodic arrangement of tetrahedral filled interstitial sites in the structure of the inverse opal, a complete reconciliation with the spectral blue-shift with the angle, photonic band gap, and material parameters is obtained when a reduced unit cell is defined based on interstitial void filling. The analysis suggests a reduced interplanar spacing (d = 1 / √ 3 D, for pore diameter D), based on the actual structure of an inverse opal in general, rather than a definition based on the inverse of an FCC packed opal. This approach provides an accurate and general description for predicting the spectral response and material parameters of ordered inverse opal photonic crystal materials.

In this work we investigate two alternative methods to remove amine molecules from as-synthesized vanadium oxide nanotubes (VONTs). Thermal treatment results in the formation of polycrystalline nanorods (poly-NRs) and ion exchange reactions with NaCl result in the formation of Na-VONTs. The removal of amine molecules is confirmed by monitoring the inorganic and organic phase changes and decomposition, respectively, using electron microscopy, IR spectroscopy and X-ray diffraction analyses. We compare the electrochemical performance of as-synthesized VONTs, poly-NRs and Na-VONTs. This work demonstrates that the presence of amine molecules within the layers of vanadium oxide impedes the intercalation of lithium ions, and that their removal results in a significant improvement in electrochemical characteristics. Out of the three vanadium oxide nanostructures investigated, poly- NRs exhibit the most promising results for practical use as a cathode material.

Oxide phase nanowires are important for applications ranging from optoelectronics to water splitting, but prove difficult to grow in high density with good crystalline quality and phase purity. Heterogeneous catalysts are typically required to nucleate growth. This work demonstrates that dispersions of oxide nanowires can be formed directly from solution processed oxide thin films. We also examine the effect of changes in applied pressure between a solution processed vanadium oxide thin film and a surface-contacted glass coupon on the catalyst-free formation of interconnected sodium vanadate nanowire structures by interdiffusion. Under different applied pressures, meshes of high quality crystalline oxide nanowires formed on the surface, and we examine the nature of phase conversion and nanostructure growth including larger shards composed of multiple conjoined nanowires are also examined. The optical properties of the oxides NWs formed by interdiffusion from oxide thin films show promising properties for application as antireflective coatings across a broadband spectral range. This interdiffusion technique is effective for high quality oxide nanowire growth without catalysts directly from insulating or conducting thin films by direct contact with a source of diffusing species.

Transparent thin films can now be site-selectively patterned and positioned on surface using mask-defined electrodeposition of one oxide and overcoating with a different solution-processed oxide, followed by thermal annealing. Annealing allows an interdiffusion process to create a new oxide that is entirely transparent. A primary electrodeposited oxide can be patterned and the secondary oxide coated over the entire substrate to form high color contrast coplanar thin film tertiary oxide. The authors also detail the phase formation and chemical state of the oxide and how the nature of the electrodeposited layer and the overlayer influence the optical clearing of the patterned oxide film.

Heterogeneous multilayered oxide channel materials have enabled low temperature, high mobility thin film transistor technology by solution processing. The authors report the growth and characterization of solution-based, highly uniform and c-axis orientated zinc oxide (ZnO) single and multilayered thin films. Quasisuperlattice (QSL) metal oxide thin films are deposited by spin-coating and the structural, morphological, optical, electronic, and crystallographic properties are investigated. In this work, the authors show that uniform, coherent multilayers of ZnO can be produced from liquid precursors using an iterative coating-drying technique that shows epitaxial-like growth on SiO2, at a maximum temperature of 300 °C in air. As QSL films are grown with a greater number of constituent layers, the crystal growth direction changes from m-plane to c-plane, confirmed by x-ray and electron diffraction. The film surface is smooth for all QSLs with root mean square roughness

In this short review, we overview some advancements made in Li-ion battery anode development, where the structural arrangement of the material plays an important role. Specifically, we summarise the benefits of 3D macroporous structure imposed the anode material, in order to improve ionic and electronic conductivity in the absence of conductive additives and binders. Two anode materials are overviewed: TiO 2 and GeO 2 . These are either high capacity anode materials or accessible, abundant materials that are capable of very stable and long-term cycling. We have focused this review on 3D inverse opal structures of these anodes and summarise their enhanced behaviour by comparing their performance metrics to a range of nanoscale and porous analogues of these materials.

New oligosilylgermane compounds with weak Ge–H bonds have been used as precursors for the rapid synthesis of germanium (Ge) nanowires in high yields (>80%), via a solution–liquid–solid (SLS) mechanism, using indium (In) nanoparticles as a seeding agent over a temperature range between 180 and 380 °C. Even at low growth temperatures, milligram quantities of Ge nanowires could be synthesized over a reaction period of between 5 and 10 min. The speed of release of Ge(0) into the reaction environment can be tuned by altering the precursor type, synthesis temperature, and the presence or lack of an oxidizing agent, such as tri-n-octylphosphine oxide (TOPO). Energy-dispersive X-ray analysis showed that silicon atoms from the precursors were not incorporated into the structure of the Ge nanowires. As both In and Ge facilitate reversible alloying with Li, Li-ion battery anodes fabricated with these nanowires cycled efficiently with specific capacities, i.e., >1000 mAh g–1

Rutile TiO2 inverse opals provide long cycle life and impressive structural stability when tested as anode materials for Li-ion batteries. The capacity retention of TiO2 inverse opals (IOs) is greater than previously reported values for other rutile TiO2 nanomaterials, and the cycled crystalline phase and material interconnectivity is maintained over thousands of cycles. Consequently, this paper offers insight into the importance of optimizing the relationship between the structure and morphology on improving electrochemical performance of this abundant and low environmental impact material. TiO2 IOs show gradual capacity fading over 1000 and 5000 cycles, when cycled at specific currents of 75 and 450 mA g−1, respectively, while maintaining a high capacity and a stable overall cell voltage. TiO2 IOs achieve a reversible capacity of ≈170 and 140 mA h g−1 after the 100th and 1000th cycles, respectively, at a specific current of 75 mA g−1, corresponding to a capacity retention of ≈82.4%. The structural stability of the 3D IO phase from pristine rutile TiO2 to the conductive orthorhombic Li0.5TiO2 is remarkable and maintains its structural integrity. Image analysis conclusively shows that volumetric swelling is accommodated into the predefined pore space, and the IO periodicity remains constant and does not degrade over 5000 cycles.

Thermally removing amine molecules that serve as chemical templates for vanadium oxide nanotubes is demonstrated to significantly improve the performance when tested as a cathode material in Li-ion battery cells. Capacity fading issues associated with blocked intercalation sites on the (010) faces of layered vanadium oxide that form the nanotubes are prevented. Thermal treatment of the nanotubes up to 600°C is shown to cause a specific conversion from nanotubes to polycrystalline nanorods and removal of the organic template. The conversion process was monitored by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy and infra-red spectroscopy. In a potential window of 4.0–1.2 V drawing 30 μA (C/30), the nanorods show improved specific capacities of ∼280 mAh g−1 with a modest 6% capacity fade compared to ∼8 mAh g−1 with 62% capacity fade for the VONTs. The improvements in specific capacity and cycling performance are due to the successful removal of amine molecules and conversion to nanorods containing nanoscale crystals. The cathode material also demonstrated enhanced energy densities (∼700 W h kg−1) compared to composites of the same overall weight, without conductive carbon additives or polymeric binders.

A binder-free cobalt phosphate hydrate (Co3(PO4)2·8H2O) multilayer nano/microflake structure is synthesized on nickel foam (NF) via a facile hydrothermal process. Four different concentrations (2.5, 5, 10, and 20 mM) of Co2+ and PO4-3 were used to obtain different mass loading of cobalt phosphate on the nickel foam. The Co3(PO4)2·8H2O modified NF electrode (2.5 mM) shows a maximum specific capacity of 868.3 C g-1 (capacitance of 1578.7 F g-1) at a current density of 5 mA cm-2 and remains as high as 566.3 C g-1 (1029.5 F g-1) at 50 mA cm-2 in 1 M NaOH. A supercapattery assembled using Co3(PO4)2·8H2O/NF as the positive electrode and activated carbon/NF as the negative electrode delivers a gravimetric capacitance of 111.2 F g-1 (volumetric capacitance of 4.44 F cm-3). Furthermore, the device offers a high specific energy of 29.29 Wh kg-1 (energy density of 1.17 mWh cm-3) and a specific power of 4687 W kg-1 (power density of 187.5 mW cm-3).

In this report we have investigated the use of Ni foam substrates as anode current collectors for Li-ion batteries. As the majority of reports in the literature focus on hydrothermal formation of materials on Ni foam followed by a high temperature anneal/oxidation step, we probed the fundamental electrochemical responses of as received Ni foam substrates and those subjected to heating at 100°C, 300°C and 450°C. Through cyclic voltammetry and galvanostatic testing, it is shown that the as received and 100°C annealed Ni foam show negligible electrochemical activity. However, Ni foams heated to higher temperature showed substantial electrochemical contributions which may lead to inflated capacities and incorrect interpretations of CV responses for samples subjected to high temperature anneals. XRD, XPS and SEM analyses clearly illustrate that the formation of electrochemically active NiO nanoparticles on the surface of the foam is responsible for this behavior. To further investigate the contribution of the oxidized Ni foam to the overall electrochemical response, we formed Co3O4 nanoflowers directly on Ni foam at 450°C and showed that the resulting electrochemical response was dominated by NiO after the first 10 charge/discharge cycles. This report highlights the importance of assessing current collector activity for active materials grown on transition metal foam current collectors for Li-ion applications.

This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic–photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided.

Structured porous materials have provided several breakthroughs that have facilitated high rate capability, better capacity retention and material stability in Li-ion batteries. However, most advances have been limited to half cells or lithium batteries, and with a single mode of charge storage (intercalation, conversion, or alloying etc.). The use of dual-mode charge storage with non-traditional material pairings, while maintaining the numerous benefits of nanoscale materials, could significantly improve the capacity, energy density, stability and overall battery safety considerably. Here, we demonstrate an efficient, high capacity full inverse opal Li-ion battery with excellent cycle life, where both the cathode and anode binder-free electrodes are composed of 3D nanocrystal assemblies as inverse opal (IO) structures of intercalation-mode V2O5 IO cathodes and conversion-mode Co3O4 IO anodes. Electrochemically charged Co3O4 IOs function as Li-ion anodes and the full V2O5/Co3O4 cell exhibits superior performance compared to lithium batteries or half cells of either IO material, with voltage window compatibility for high capacity and energy density. Through asymmetric charge–discharge tests, the V2O5 IO/Co3O4 IO full Li-ion cell can be quickly charged, and discharged both quickly and slowly without any capacity decay. We demonstrate that issues due to the decomposition of the electrolyte with increased cycling can be overcome by complete electrolyte infiltration to remove capacity fading from long term cycling at high capacity and rate. Lastly, we show that the V2O5 IO/Co3O4 IO full Li-ion cells cycled in 2 and 3-electrode flooded cells maintain 150 mA h g−1 and remarkably, show no capacity fade at any stage during cycling for at least 175 cycles. The realization of an all-3D structured anode and cathode geometry with new mutually co-operative dual-mode charge storage mechanisms and efficient electrolyte penetration to the nanocrystalline network of material provides a testbed for advancing high rate, high capacity, stable Li-ion batteries using a wide range of materials pairings.

A range of vanadium oxide nanotubes consisting of scrolled layers of primary amine functionalized xerogel have been produced by a hydrothermal treatment of a xerogel/amine mixture. The nanotubes consist of a hollow core flanked by parallel layers of scrolled vanadium oxide layers. The interlayer spacing is varied on the sub-nm scale by intercalated amines templates of various molecular lengths. High resolution transmission electron microscopy and X-ray diffraction were used to characterize the resulting nanotubes. When the molar ratio of xerogel:amine is 1:2, a maximum yield of nanotubes is produced and the interlayer spacing can be controlled. For a molar ratio of xerogel:amine of 2:1, the product contains a low yield of nanotubes and the corresponding interlayer spacing is independent of the length of the amine template. A comparison of measured interlayer distances with the actual physical length of the primary amine chains shows that interdigitation of the amines occurs.

High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.

Zinc oxide (ZnO) and its doped counterparts such as Al:ZnO are extensively investigated as indium-free alternatives for oxide electronics including solar cells, light emitting diodes and also display technologies. For the latter application, thin film transistor (TFT) devices are the building-block structures. High fidelity TFTs require conductive channel materials, with good field effect mobility for majority carriers and tunable optical transparency. Controlling growth, doping, crystallization, and thickness of thin films of these materials is required in order to improve and control physical properties, primarily electronic conductivity and optical transparency. With the advent of flexible electronics and curved TFT-based display panels, low cost, solution-processed methods are important and provide scalable coating methods on a range of substrates. This work demonstrates the changes to the morphology, crystalline structure, optical reflectivity and electrical conductance of solution-processed ZnO thin films by the inclusion of an aluminium dopant during spin-coating. The is work also determines the compositional chemical state of the Al:ZnO structures compared to ZnO using X-ray photoelectron spectroscopy in conjunction with detailed X-ray diffraction and transmission electron microscopy examination of the film morphology. We also demonstrate a method of determining the optical thickness of multilayer thin films using simple, non-destructive angle-resolved reflectance measurements. Using optical interference, the optical thickness of the multi-layered deposited ZnO and Al:ZnO can be determined and show good agreement with the thicknesses measured by transmission electron microscopy of electron transparent lamellar cross-sections. We also show the visible and near-infra red (VIS-NIR) light spectroscopy of ZnO and Al:ZnO multi-layered thin film structures grown on oxidized silicon substrates also define the growth conditions and processing to provide tunable antireflection coatings of ZnO and AZO.

The electrochemical intercalation of lithium into vanadium pentoxide was first reported in the 1970's. Over the last 40 years vanadium oxides have continued to be the subject of much research due to their desirable physical properties. Initial results with bulk V2O5 and V2O5 gels demonstrated the potential for application as a cathode material for lithium batteries. Encouraging specific capacities exceeding 250 mAh g−1 were accompanied by severe capacity fading, which prevented widespread commercial application of V2O5-containing cathodes. Following the commercial release of the Li-ion battery, the development of layered materials that reversibly intercalated lithium, and the resurgence in nanoscale materials for Li-ion and alternative batteries, have opened new opportunities for the examination of the influence of material structure on cell performance. Recent decades have witnessed advances in the control of shape, structure and function of Li-ion battery materials. This review details the synthesis and structural properties of vanadium oxides, one of the model layered battery materials, and reviews the synthesis and structure of vanadium oxides and related polymorphs, bronzes and phases. Their electrochemical characteristics under a wide range of conditions are assessed and compared as positive electrode materials in lithium and lithium-ion batteries up to the present day.

A key element in the rational design of hybrid organic-inorganic nanostructures, is control of surfactant packing and adsorption onto the inorganic phase in crystal growth and assembly. In layered single crystal nanofibers and bilayered 2D nanosheets of vanadium oxide, we show how the chemisorption of preferred densities of surfactant molecules can direct formation of ordered, curved layers. The atom-scale features of the structures are described using molecular dynamics simulations that quantify surfactant packing effects and confirm the preference for a density of 5 dodecanethiol molecules per 8 vanadium attachment sites in the synthesised structures. This assembly maintains a remarkably well ordered interlayer spacing, even when curved. The assemblies of interdigitated organic bilayers on V2O5 are shown to be sufficiently flexible to tolerate curvature while maintaining a constant interlayer distance without rupture, delamination or cleavage. The accommodation of curvature and invariant structural integrity points to a beneficial role for oxide-directed organic film packing effects in layered architectures such as stacked nanofibers and hybrid 2D nanosheet systems.

Vanadium oxide nanotubes (VONTs) have been successfully synthesized by hydrothermal treatment of a mixture of vanadium oxide xerogel and nonylamine. Traditionally dodecylamine and hexadecylamine are used as the structure maintaining template. In this study, however, evidence of high quality nanotubes templated with nonylamine is presented. Thermogravimetric analysis was used to determine the temperature at which the amine molecules can be removed from the nanotubes. The removal of amines is desirable as heavy functionalization of VONTs by amine molecules can impede the intercalation of lithium ions. The removal of the amine chains resulted in a change in morphology from pristine nanotubes to polycrystalline vanadium oxide nanorods. High resolution transmission electron microscopy was used to characterize the VONTs before and after annealing to high temperatures. Fourier transform infrared spectroscopy confirmed the removal of the amine template after annealing. Galvanostatic discharge tests were performed to compare the electrochemical behavior of bulk V2O5 powder, VONTs and polycrystalline nanorods (poly-NRs). A comparison of their specific capacity values after the first discharge is also presented.

Embedding 2D layered materials into polymers and other materials as composites has resulted in the development of ultrasensitive pressure sensors, tunable conductive stretchable polymers, and thermoelectric coatings. As a wettable paint or ink, many 2D materials may be penciled, printed, or coated onto a range of surfaces for a variety of applications. However, the intrinsic conductive properties of painted coatings using 2D and layered materials are not completely understood, and conductive polymer additives may mask underlying properties such as directional conductivity. We report a process for making a paint from solvent-exfoliated Bi2Te3 into solution-dispersible 2D and few-layer (multiple quintuple) nanosheet inks, that form smooth, uniform paint blends at several concentrations of Bi2Te3. The individual solvent-exfoliated nanosheets are edge-coated by (poly)ethylene glycol to produce a paint, stable over extended period in solution. Electrical transport is found to be sensitive to aspect ratio, and conduction along the painting direction is suppressed for longer strips so long as the aspect ratio is high (4-10× or more), but for short and wide paint strips (aspect ratio ≤1), conductance is improved by a factor of 3×. Square 2D paint regions show no clear directional preference for conductance at room temperature but are markedly affected by higher temperatures. Conductivity along a preferential conduction pathway through the nanosheet ensemble is modulated by 2D nanosheet stacking along the direction of paint application for a given aspect ratio. This paint and insights into geometrical 2D composite conduction may have implications for conductive composites, thermoelectrics, and writable circuits using 2D material paints or inks. Fil: Carroll, Elaine. University College Cork; Irlanda Fil: Buckley, Darragh. University College Cork; Irlanda Fil: Mogili V., Vishnu N.. Centro Nacional de Pesquisa em Energia e Materiais. Brazilian Nanotechnology National Laboratory; Brasil Fil: McNulty, David. University College Cork; Irlanda Fil: Moreno, Mario Sergio Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Glynn, Colm. University College Cork; Irlanda Fil: Collins, Gillian. University College Cork; Irlanda Fil: Holmes, Justin D.. University College Cork; Irlanda. Tyndall National Institute; Irlanda. Trinity College Dublin; Irlanda Fil: Razeeb, Kafil M.. Tyndall National Institute; Irlanda Fil: O'Dwyer, Colm. University College Cork; Irlanda. Tyndall National Institute; Irlanda