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Two-dimensional van der Waals heterostructures (vdWHs) with tunable band alignment have the potential to be benignant in the development of minimal multi-functional and controllable electronics, but they have received little attention thus far. It is crucial to characterize and control the band alignment in semiconducting vdWHs, which determines the electronic and optoelectronic properties. The future success of optoelectronic devices will require improved electronic property control techniques, such as using an external electric field or strain engineering, to change the electronic structures directly. Herein, we review heterostructures fabricated as transition metal dichalcogenides (TMDCs) as one of their constituent monolayers with other notable 2D materials that can transfer from type-II to type-III (type-IIItype-II) band alignment when a biaxial strain or electric field is applied.

Magnetic nanostructured materials have found numerous biomedical applications. However, the influence of a magnetic field on the inhibition of pathogenic microorganisms has been poorly explored. Zinc and Iron nano-structured oxides have been widely used due to their biocompatibility and their excellent optoelectronic and magnetic properties. Nevertheless, little effort has been devoted to demonstrate their antibacterial activity at doses that are not harmful to mammalians. In this work, ZnO, Fe3O4 (MNPs) and ZnO@Fe3O4 (NCs) were synthesized and fully characterized. The materials exhibit good antibacterial activity to inhibit the growth of Staphylococcus aureus (S. aureus) and Helicobacter pylori (H. pylori) both, as planktonic cells and as biofilms structures at low doses. The photocatalytic activity of the materials (NCs) was demonstrated when radiated suspensions of NCs and microorganisms (MOs) exhibited higher inhibition growth of MOs in comparison to non-radiated assays. The materials show better antibacterial activity for biofilm growth inhibition in comparison to commercially available antibiotics. Magnetic antimicrobial films were fabricated by in situ deposition of MNPs in Arabic gum (AG) solution. The films exert enhanced antibacterial activity against S. aureus growth due to Fe3+lixiviation and magnetic disruption. Regarding the biocompatibility of the materials, ZnO modifies significantly biochemical parameters in Wistar rats after acute administration. Our results show that the composite ZnO@Fe3O4 at low doses: (a) exerts an optimum inhibition on the biofilm formation of microorganisms due to its synergetic activity of lixiviation of ions and oxidative activity; (b) good biocompatibility of the composite with living cells. These properties suit ZnO@Fe3O4 as potential candidates for the development of new anti-biofilm formulation.

We report on the preparation and optimization of low temperature (

Electromodulation (EM) spectroscopy, a powerful technique to monitor the changes in polarizability p and dipole moment u of materials upon photo-excitation, can bring direct insight into the excitonic properties of materials. However, extracting Δp and Δu from the electromodulation spectrum relies on fitting with optical absorption of the materials where optical effect in different device geometries might introduce large variation in the extracted values. Here, we demonstrate a systematic electromodulation study with various fitting approaches in both commonly adopted reflection and transmission device architectures. Strikingly, we have found that the previously ascribed continuum state threshold from the deviation between the measured and fitting results is questionable. Such deviation is found to be caused by the overlooked optical interference and electrorefraction effect. A generalized electromodulation model is proposed to incorporate the two effects, and the extracted Δp and Δu have excellent consistency in both reflection and transmission modes in all organic film thicknesses., The development of a generalized electromodulation (EM) spectroscopy model that accurately extracts material parameters for organic electronics remains a challenge. Here, the authors report an EM model that enhances parameter extraction accuracy by accounting for optical interference effects.

Color-tunable semiconductor quantum dots (QDs) are highly attractive for a wide range of applications including imaging, sensing, and lighting. Herein, we reported a facile synthesis of copper-doped zinc sulfide quantum dots (ZnS:Cu QDs) with tunable emission colors, using a microwave-assisted one-pot reaction. 3-mercaptopropionic acid (MPA) was used as a stabilizer agent and sulfide source for the formation of ZnS:Cu QDs. The photoluminescence of ZnS:Cu QDs showed a clear red-shift as increasing Cu concentration, which can be controlled by microwave irradiation time. As increasing the irradiation time, the emission color (peak) of ZnS:Cu QDs changed from blue (500 nm) to green (540 nm), yellow (580 nm), and to orange-red (595 nm). The obtained ZnS:Cu QDs were highly luminescent, as evidenced by their high quantum yields. The potential utility of ZnS:Cu QDs as a novel lighting source was demonstrated in a near-UV chip-based white light-emitting diode.

Antimony sulfide (Sb2S3) has been employed for materials of the potential anode in sodium-ion batteries (SIBs) because it possesses a high theoretical capacity. However, volume variations coupled with sluggish diffusion kinetics cause rapid capacity degradation and cyclic instability during the sodiation/desodiation process. Here, we introduce a simple strategy to develop nitrogen-doped carbon-encapsulated antimony sulfide nanowire (Sb2S3@N-C) composites for the anode in SIBs. The resulting composites display excellent electrochemical characteristics with remarkable rate capability, ultrahigh capacity, and excellent stability derived from the synergistic effect between a one-dimensional Sb2S3 nanowire and a nitrogen-doped carbon, thus demonstrating the Sb2S3@N-C composites as a material with potential characteristics for the anode in next-generation storage devices. Electrochemical analysis reveals that pseudocapacitive behavior dominates the overall electrochemical process of the Sb2S3@N-C composites, which is responsible for the fast capacitive charge storage. The authors acknowledge support from the Cultivation Project of National Engineering Technology Center (Grant 2017B090903008), National Natural Science Foundation of China Program (Grant 51602111), Special Fund Project of Science and Technology Application in Guangdong (Grant 2017B020240002), Basic Research Project of Knowledge Innovation Program of Shenzhen City (Grant JCYJ20160229165250876), and Xijiang R&D Team.

Photon management of perovskite solar cells (PSCs) is studied by the use of nanohole front contact, which allows improving the JSC of the PSC by providing an improved light incoupling. The front contact integrated with spherical nanocone shaped holes represent a refractive index grating allowing for light incoupling approaching unity while minimizing reflection losses. Besides, the front contact has a comparable refractive index (n~2.5) with the perovskite absorber, which minimizes the front reflections in PSC. Optics and optimization of front contact and solar cell are investigated by three-dimensional (3D) finite-difference time-domain (FDTD) simulations whereas finite element method simulations are used to study the electrical response of the device. Investigations reveal a maximum light incoupling enhancement of 10~12% for the optimized PSC, leading to 10 to 27% JSC enhancement with respect to the planar reference PSC.

Optical field enhancement plays a key role in applications such as chemical and biological detection, imaging or alternatively exchange of information and communication. Historically, thanks to plasmonic resonances, metals have dominated applications related to field enhancement and confinement for sensing and imaging [1]–[4]. Dielectrics, on the other hand, found a prominent role mainly in communication and waveguiding applications because of the associated low optical losses [5], [6]. With the growing demands for chemical and biological sensing at higher sensitivity and selectivity, recent designs such as hybrid systems with the Tamm plasmons [7], [8] or resonant all-dielectric multilayers [9]–[11] are gaining prominence. Such systems can be synthesized and optimized with the aid of the admittance formalism, commonly practiced in optical thin film design, leading to huge optical fields when working under total internal reflection [12]–[16]. Following our recent synthesis method, wherein a zero-admittance layer is deposited on a Bragg mirror [12], [17], we will explore the resulting field enhancement and confinement parameters, and therefore fully characterize the associated large ultra-sharp optical resonances. The strength and sharpness of these resonances are assets for low detection applications but require a well-controlled incident illumination and a highly accurate control over the geometric parameters of the multilayers. After evaluating such boundaries [18], [19], we will fabricate and operate with optimized resonant dielectric multilayers in sensing configurations to evaluate both the achievable sensitivity and limit of detection. We will present our first experimental results involving different solutions with concentrations as low as 0.03%, corresponding to a refractive index variation of $6\times 10^{-5}$ [17]. The strong agreement with the theoretical predictions demonstrates the validity and utility of the presented sensing approach.

High electrochemical performance energy storage devices coupled with low cost and high safety operation are in urgent need due to the increasing demand for flexible and wearable electronics. For these applications lithium-ion and sodium-ion batteries are vastly limited due to their relatively low power density and security risks. On the other hand, conventional supercapacitors are suitable for flexible and wearable electronics due to their high power density while their low energy density has hindered their wide applications. Lithium or sodium ion hybrid supercapacitors are promising energy storage devices that benefit from the combined high energy density of batteries and high power density of supercapacitors. However, the use of organic electrolytes and shortage of lithium resources are expected to limit their widespread commercialization for flexible and wearable electronics. Here, for the first time, we introduce a safe and flexible solid-state zinc ion hybrid supercapacitor (ZHS) based on co-polymer derived hollow carbon spheres (HCSs) as the cathode, polyacrylamide (PAM) hydrogel as the electrolyte and Zn deposited on carbon cloth as the anode. Owing to the high surface area of the HCSs and the hollow structure which improves the ion adsorption and desorption kinetics of the cathode, the flexible solid-state ZHS delivers a highest capacity of 86.8 mA h g−1 and a maximum energy density of 59.7 W h kg−1 with a power density of 447.8 W kg−1. Besides, it displays excellent cycling stability with 98% capacity retention over 15 000 cycles at a current density of 1.0 A g−1. Moreover, the solid-state ZHS is flexible enough to sustain various deformations including squeezing, twisting and folding due to the use of flexible electrodes and electrolytes. Our study unveils a pioneering flexible solid-state ZHS with high safety, which is a promising candidate for flexible and wearable energy storage devices.

Although both are based on Zn, Zn–air batteries and Zn–ion batteries are good at energy density and power density, respectively. Here, we adopted Ar–plasma to engrave a cobalt oxide with abundant oxygen vacancies (denoted as Co3O4–x). The introduction of oxygen vacancies to cobalt oxide not only promotes its reversible Co–O ↔ Co–O–OH redox reaction but also leads to good oxygen reduction reaction and oxygen evolution (ORR/OER) performance (a half-wave potential of 0.84 V, four-electron transfer process for ORR, and 330 mV overpotential, 58 mV·dec–1 Tafel slope for OER). We then constructed a battery system based on both Zn–Co3O4–x and Zn–air electrochemical reactions. The hybrid battery reveals both a high-power density of 3200 W·kg–1 and high-energy density of 1060 Wh·kg–1. Furthermore, the developed flexible solid-state hybrid batterydemonstrates good waterproof and washable ability (99.2% capacity retention of after 20 h water soaking test and 93.2% capacity retention after 1 h washing test). Interesti...

Well aligned 1D ZnO nanostructures are important for optoelectronic and nanoscale electronic devices. In this report, 1D ZnO nanorods were synthesized by very simple, low cost, low temperature hydrothermal process. An effect of concentration, growth time, growth temperature, seed layer annealing, and seed layer thickness was investigated. The synthesized ZnO nanorods were characterized by scanning and transmission electron microscopies, X-ray diffraction, Raman and ultraviolet–visible spectroscopies. Growth parameters were found to influence strongly on the morphology, orientation, diameter, length, and density of the ZnO nanorod arrays. The growth temperature 80–90°C, seed layer annealing at 300–400°C, growth time 3 h, 0.025 M precursor concentration, and 0.2–0.3 M seed layer solution concentrations are more favorable conditions for better orientation and excellent crystallinity of the ZnO nanorods.

Synthesis of zinc oxide (ZnO) nanostructures is reported by electrochemical deposition from an aqueous electrolyte in presence of graphene oxide (GO) with varying oxidation degree. The properties of hybrids were investigated by scanning electron microscopy, X-ray diffraction, Raman, Fourier-Transform Infrared and X-ray photoelectron spectroscopy techniques and photocatalytic measurements. The results indicated the electrodeposition of ZnO in presence of GO with increased oxygen content led to marked differences in the morphology while Raman measurements indicated an increased defect level both in the ZnO and the electrochemically reduced GO (ErGO) within the hybrids. The decrease in C/O atomic ratio of GO (from 0.79 to 0.71) employed for the electrodeposition of ZnO resulted in an increase in photocatalytic efficiency for methylene blue degradation under UV irradiation from 4-folds to 10-folds with respect to non-hybridized ZnO. The observed synergetic effect of cathodic deposition potential and oxygen content in GO towards improving the photocatalytic activity of immobilized ZnO is expected to contribute to further development of more effective deposition approaches for the preparation of high performance hybrid nanostructures.

The exploitation of a high-efficient, low-cost, and stable non-noble-metal-based catalyst with oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) simultaneously, as air electrode material for a rechargeable zinc–air battery is significantly crucial. Meanwhile, the compressible flexibility of a battery is the prerequisite of wearable or/and portable electronics. Herein, we present a strategy via single-site dispersion of an Fe–Nx species on a two-dimensional (2D) highly graphitic porous nitrogen-doped carbon layer to implement superior catalytic activity toward ORR/OER (with a half-wave potential of 0.86 V for ORR and an overpotential of 390 mV at 10 mA·cm–2 for OER) in an alkaline medium. Furthermore, an elastic polyacrylamide hydrogel based electrolyte with the capability to retain great elasticity even under a highly corrosive alkaline environment is utilized to develop a solid-state compressible and rechargeable zinc–air battery. The creatively developed battery has a low charge–discha...

In this work, we have synthesized Cd1–xGaxO1+δ alloy thin films at room temperature over the entire composition range by radio frequency magnetron sputtering. We found that alloy films with high Ga contents of x > 0.3 are amorphous. Amorphous Cd1–xGaxO1+δ alloys in the composition range of 0.3 < x < 0.5 exhibit a high electron mobility of 10–20 cm2 V–1 s–1 with a resistivity in the range of 10–2 to high 10–4 Ω cm range. The resistivity of the amorphous alloys can also be controlled over 5 orders of magnitude from 7 × 10–4 to 77 Ω cm by controlling the oxygen stoichiometry. Over the entire composition range, these crystalline and amorphous alloys have a large tunable intrinsic band gap range of 2.2–4.8 eV as well as a conduction band minimum range of 5.8–4.5 eV below the vacuum level. Our results suggest that amorphous Cd1–xGaxO1+δ alloy films with 0.3 < x < 0.4 have favorable optoelectronic properties as transparent conductors on flexible and/or organic substrates, whereas the band edges and electrical co...

MoS2 is an interesting material due to its intriguing properties and potential applications. Theoretical and experimental studies demonstrated p-type of Ag doped MoS2 system. Band structures, density of states and I-V characteristics confirmed that Ag is an efficient acceptor and indirect band gap is reduced with Ag doping. Formation energy is negative which indicates the substitution reactions could be possible. MoS2 is a strong photocatalyst for O2 production and the oxidation ability is enhanced with Ag doping. Mo100-xAgxS2 (x = 0.0 to 10) thin films seems to be stacked of many layers and XRD patterns justify hexagonal crystal structure. EDX and XPS measurements ensured the films are composed of Mo, S and Ag. Rectification is observed for Au/Mo100-xAgxS2 and the forward current decreases with Ag. The built-in potential is just opposite side to undoped MoS2 insights p-MoS2. Thus Ag doped MoS2 would enable for fabrication of efficient electronic, photocatalytic and optoelectronic devices.

We present a strategy for photon management in front contact of perovskite solar cells (PSCs) compatible with tandem and flexible PSCs capable of optimizing device characteristics while providing an additional mechanism to overcome excessive focusing that affects the device’s photostability. Rigorous validation of the numerical modeling used was performed by fabricating PSCs in a superstrate configuration optimized to reach high performance, ECE = 17.4%, VOC = 1.02 V, JSC = 22.3 mA/cm2, and FF = 77%. These 3D electromagnetic simulations combining the finite-difference time-domain (FDTD) and finite element method (FEM) techniques provide detailed insights of the photonic and electrical effects in PSCs. Numerical optimization of the dual capabilities of a novel nanostructured front contact enables control of the absorbed power density distribution to maximize efficiency while simultaneously minimizing nanostructure-related sub-wavelength focusing effects. In-depth analysis of the proposed photon management reveals enhanced electrical characteristics to maximize charge extraction leading to JSC enhancements of ~15 that can be as high as 33% for ultra-thin active layers suitable for flexible PSCs compared to planar PSCs performance. Furthermore, we show that the design of the front contact layer’s nanostructure enables control of the power density distribution in the device to engineer PSCs' photostability without compromising performance enhancements afforded by the nanophotonic front contact. Details of the nanophotonic front contact, device, and fabrication process are provided.

Flexible supercapacitors with high areal capacitance are a promising approach for wearable energy-storage technology due to the limitation of the surface area of the human body (about 2 m2). Meanwhile, a tolerance to deformation and mechanic damage is critical for wearable applications. However, it is still a challenge to achieve supercapacitors with outstanding electrochemical performance and wearability, simultaneously. To solve this problem, we report high-performance, flexible, and tailorable solid-state supercapacitors enabled by Co3O4@PPy nanorod bundle arrays immobilized on carbon fiber cloth (CFC). Furthermore, a solid-state asymmetric supercapacitor was assembled using a freestanding Co3O4@PPy electrode, a freestanding porous carbon electrode, and PVA gel electrolyte. Benefiting from a 3D structure and the synergetic contribution of the Co3O4 nanorods and electrically conductive PPy layer, the Co3O4@PPy electrode and our developed supercapacitor exhibit a high areal capacitance of 6.67 F cm−2 at a current density of 2 mA cm−2, and 2.47 F cm−2 at 4 mA cm−2, respectively, as well as excellent rate capability. More importantly, the solid-state supercapacitor can be tailored into several units and various shapes. Each unit retains its original electrochemical performance. This work provides a new route to wearable energy-storage technology.

The Zn/Co3O4 battery is one of the few aqueous electrolyte batteries with a potential >2 V voltage. Unfortunately, so far, all reported Zn/Co3O4 batteries are using an alkaline electrolyte, resulting in poor cycling stability and environmental problems. Here, we report a Co(III) rich-Co3O4 nanorod material with vastly improved electrochemical kinetics. Zn/Co(III) rich-Co3O4 batteries can work well in ZnSO4 with a CoSO4 additive aqueous solution as a mild electrolyte, delivering a high voltage of 2.2 V, a capacity of 205 mA h g−1 (Co3O4) and an extreme cycling stability of 92% capacity retention even after 5000 cycles. Further mechanistic study reveals a conversion reaction between in situ formed CoO and Co3O4, which has never been observed in an alkaline Zn/Co3O4 battery. Subsequently, a flexible solid-state battery is constructed and reveals high flexibility and a high energy density of 360.8 W h kg−1 at a current density of 0.5 A g−1. Our research initiates the first Zn/Co3O4 battery working in a mild electrolyte, resulting in excellent electrochemical performance. It also indicates that the electrochemical kinetics can be effectively enhanced by fine tuning the atomic structure of electrode materials, opening a new door to improve the performance of aqueous electrolyte batteries.

The performance of quasi-2D perovskite light emitting diodes (LEDs) with mixed small cations, cesium and formamidinium (FA), is significantly affected by their ratio. The best devices obtained for Cs:FA ratio of 1:1 exhibit a maximum external quantum efficiency (EQE) of 12.1%, maximum luminance of 15 070 cd m−2 and maximum current efficiency of 46.1 cd A−1, which is significantly higher (about 3 times) compared to devices with FA only (maximum EQE of 4.1%, maximum luminance of 4521 cd m−2) and Cs-only (maximum EQE of 4.0%, maximum luminance of 4886 cd m−2). The photoluminescence quantum yield of the Cs:FA 1:1 sample is similarly enhanced, 21.3% compared 5.4% and 6%, for FA-only and Cs-only samples, respectively. It can be observed that the Cs:FA ratio significantly affects the crystallization of the perovskite, with the optimal 1:1 ratio resulting in the formation of tetragonal Cs0.5FA0.5PbBr3 phase (different from cubic FAPbBr3 and orthorhombic CsPbBr3) with pronounced preferential orientation as well as a significant reduction in the trap density, which leads to a substantial improvement in the light- emitting performance.

In this study, detailed investigations of low-frequency noise (LFN) characteristics of hybrid chemical vapor deposition (HCVD)- and solution-grown CH3NH3PbI3 (MAPI) solar cells are reported. It has been shown that LFN is a ubiquitous phenomenon observed in all semiconductor devices. It is the smallest signal that can be measured from the device; hence, systematic characterization of the LFN properties can be utilized as a highly sensitive nondestructive tool for the characterization of material defects in the device. It has been demonstrated that the noise power spectral densities of the devices are critically dependent on the parameters of the fabrication process, including the growth ambient of the perovskite layer and the incorporation of the mesoscopic structures in the devices. Our experimental results indicated that the LFN arises from a thermally activated trapping and detrapping process, resulting in the corresponding fluctuations in the conductance of the device. The results show that the presenc...

The thin film of Sb2Se3 was deposited by thermal evaporation method and the film was annealed in N2 flow in a three zone furnace at a temperature of 290°С for 30 min. The structural properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (ТЕМ), X-ray diffraction (XRD) and Raman spectroscopy, respectively. It is seen that the as-deposited film is amorphous and the annealed film is polycrystalline in nature. The surface of Sb2Se3 film is oxidized with a thickness of 1.15 nm investigated by X-ray photolecetron spectroscopy (XPS) measurement. Spectroscopic ellipsometry (SE) and UV–vis spectroscopy measurements were carried out to study the optical properties of Sb2Se3 film. In addition, the first principles calculations were applied to study the electronic and optical properties of Sb2Se3. From the theoretical calculation it is seen that Sb2Se3 is intrinsically an indirect band gap semiconductor. Importantly, the experimental band gap is in good agreement with the theoretical band gap. Furthermore, the experimental values of n, k, e1, and e2 are much closer to the theoretical results. However, the obtained large dielectric constants and refractive index values suggest that exciton binding energy in Sb2Se3 should be relatively small and an antireflective coating is recommended to enhance the light absorption of Sb2Se3 for thin film solar cells application.

The finite difference time domain (FDTD) method presents attractive advantages for analysis of the spectroscopic ellipsometry (SE) response of complex, non-planar samples including generality and suitability to address complex structures as well as non-linear effects and/or non-periodic morphologies. However, it is imperative to advance our understanding, and more importantly, to design strategies to improve the computational time of FDTD method calculations. In a previous report we show the ability to simulate the SE response of prototypical samples based on far-field projections of near-field simulation based on the FDTD method with accuracy equivalent to ∼0.5 monolayer precision in film thickness up to 70° angle of incidence (AoI). In this contribution, we provide a refined strategy that results in ∼3 orders of magnitude improvement in the determination of the SE data as estimated by the χ 2 figure of merit for modeling of SE data at angles as large as 80° AoI with respect to the standard solution. Significantly the proposed strategy also provides improvement in the computation time that speeds up by a factor ∼4× at 70° AoI but that can be as large as ∼20× for 40° AoI.

1D ZnO nanostructures have been considerable interests due to their unique structures and properties as well as potential applications as building blocks of nanodevices. The Zn1−xLixO NR arrays were grown on p-Si substrate by an inexpensive environment friendly hydrothermal process followed by forming Au/Zn1−xLixO NRs Schottky photodiodes. The diodes show excellent rectifying property in dark and the rectification to be 1.19 × 102 and 6.26 × 102 at 2.4 V, for Au/ZnO and Au/LZO NRs diodes, respectively. It is interesting that Li doped diode shows negative shift of the turn on voltage (Von) and the rapidly increasing forward current as well as low leakage current which are of great benefit to minimize the power loss and an improving switching characteristics of rectifier devices. The obtained ideality factor is greater than unity. The value of barrier height obtained from I–V measurements is smaller than the value obtained from C–V measurements. The responsivity is higher for Li doped diode (0.13 A/W) than undoped (0.05 A/W) even the commercial GaN UV detector (0.1 A/W). Thus, good crystallinity and excellent Schottky diode rectifying properties of Au/ZnLiO NRs diode on p-Si substrate, enabling efficient electronics nanodevices and nanoscale UV-photodetection sensors.

Ruthenium(II) tris(bipyridyl) cationic complex (Ru(bpy)32+) incorporated UiO-67 (Universitetet i Oslo) nanoscale metal–organic frameworks (NMOFs) with an average diameter of ∼92 nm were developed as theranostic nanoplatform for in vitro two-photon fluorescence imaging and photodynamic therapy. After incorporation into porous UiO-67 nanoparticles, the quantum yield, luminescence lifetime, and two-photon fluorescence intensity of Ru(bpy)32+ guest molecules were much improved owing to the steric confinement effect of MOF pores. Benefiting from these merits, the as-synthesized nanoparticles managed to be internalized by A549 cells while providing excellent red fluorescence in cytoplasm upon excitation with 880 nm irradiation. Photodynamic therapeutic application of the Ru(bpy)32+-incorporated UiO-67 NMOFs was investigated in vitro. The Ru(bpy)32+-incorporated UiO-67 NMOFs exhibited good biocompatibility without irradiation while having good cell-killing rates upon irradiation. In view of these facts, the deve...

A new refractive index sensor based on all-dielectric interference coating is presented. The sensor performance is experimentally demonstrated. It has been verified and quantified by experiment. It has potential be widely used in sensing application.

Cancer treatment by magnetic hyperthermia offers numerous advantages, but for practical applications many variables still need to be adjusted before developing a controlled and reproducible cancer treatment that is bio-compatible (non-damaging) to healthy cells. In this work, Fe3O4 and CoFe2O4 were synthesized and systematically studied for the development of efficient therapeutic agents for applications in hyperthermia. The biocompatibility of the materials was further evaluated using HepG2 cells as biological model. Colorimetric and microscopic techniques were used to evaluate the interaction of magnetic nano-materials (MNMs) and HepG2 cells. Finally, the behavior of MNMs was evaluated under the influence of an alternating magnetic field (AMF), observing a more efficient temperature increment for CoFe2O4, a desirable behavior for biomedical applications since lower doses and shorter expositions to alternating magnetic field might be required.

Zinc-air batteries (ZABs) have the advantages of low price, environmental friendliness, and high energy density that enables great potential for the application of energy storage devices. Unfortunately, the main limitation of ZABs is the low kinetics of air cathode, including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), making it necessary to develop catalysts with excellent performance to speed up the reaction rates and improve their efficiency. For these purposes, cobalt-based carbon has the advantages of low cost, high activity, and stability, which are suitable for oxygen electrocatalysts. In this review, the basic mechanisms of ORR and OER electrocatalysis are introduced and analyzed, and the development of cobalt-based carbon materials used as electrocatalysts in ZABs in recent years is reviewed, including cobalt oxide–based carbon, cobalt-nitrogen–doped carbon (Co–N–C), and cobalt bimetallic–based carbon. In addition, we review the use of in situ/in operando characterization techniques applied to trace the catalytic reactions. Finally, we provide an account of the current challenges and future perspectives for the design of new types of high efficiency and bifunctional electrocatalysts.

In this paper, systematic investigations on the fabrication and characterization of high performance TiO2 nanorod array perovskite solar cells (NAPSCs) are reported. The TiO2 nanorods, of length around 350–400 nm, were grown by solvothermal technique directly on glass/FTO substrates. From the scanning transmission electron microscopy (STEM) we demonstrate that excellent crystallinity for the TiO2 nanorods can be produced using the solvothermal technique. Precursor consisting of a mixture of PbI2, CH3NH3I (MAI) and CH3NH3Cl (MACl) was used for the growth of perovskite thin films on the glass/FTO/TiO2 nanorod array (TiO2-NA) substrates. It is found that the morphology and quality of the perovskite layer depend strongly on the concentration of MACl in the precursor. Experimental studies on femtosecond transient absorption (fs-TA) indicate that the incorporation of TiO2-NA greatly enhances the collection efficiency of the photo-generated carriers due to substantial increase of interfacial area between the perovskite and TiO2-NA, leading to a reduction in carrier diffusion distance. It is shown to be the key factor that the proposed technique facilitates the use of a thicker perovskite absorber layer (∼500 nm) without compromising on the series resistance. Detailed J–V characterization shows that the NAPSCs exhibit negligible hysteresis with a power conversion efficiency (PCE) >19% for the champion device.

Novel hybrid core-shell nanoarchitectures were fabricated by a simple two-step electrochemical approach: first ZnO nanorod core was electrodeposited from Zn(NO3)2 solution; further, the core nanoarray was coated with a shell based on polypyrrole hybridized with graphene oxide by electropolymerization. The properties of the core/shell nanoarchitectures were studied as a function of the core properties induced by electrodeposition parameters. The ZnO nanostructures showed improved crystallinity and c-axis preferred orientation with increasing cathodic deposition potential while the increased deposition duration resulted in a morphology transition from nanorod to pyramidal shape. The electrochemical activity of the core/shell arrays was found to increase with the deposition potential of ZnO core but decreased when morphology changed from nanorod to pyramid shape. The photocatalytic results showed improved activity for the core/hybrid shell nanoarrays with respect to ZnO and ZnO/PPy ones. The degradation rate for methylene blue decreased with prolonged deposition duration of the core. The obtained results highlight the importance of electrochemical tuning of ZnO-based core/shell nanoarrays for improved performance in electrochemical and photocatalytic applications.

Novel hybrid architectures based on ZnO nanostructures supported on reduced graphene oxide films are reported by a facile two-step aqueous electrochemical approach. Graphene oxide (GO) obtained by oxidizing graphite with either H2SO4:H3PO4 mix or H2SO4 was subjected to electrochemical reduction (ErGO) by constant potential and sweeping potential methods and further employed as seeding layer for electrodeposition of ZnO nanorods. The results showed the GO reduction rate was markedly influenced by oxygen content while Infrared spectroscopy indicated the sweeping potential was effective in removing the carbonyl and alkoxy groups but also as more defect-inducing reduction approach than constant potential, according to the Raman measurements. The subsequent electroreduction of ErGO during the electrodeposition of ZnO resulted in interfacial interaction between the seed layer and ZnO nanorods. H2SO4:H3PO4 mix induced a less disrupted graphitic plane in GO which proved beneficial for the growth of higher density ZnO nanorods with improved crystalline quality. By controlling the chemical introduction/electroreduction conditions for oxygen groups in GO materials, the interfacial interaction with ZnO nanorods and their properties could be tailored in order to obtain high performance nanoplatforms.

Bismuth chalcogenides are promising materials for thermoelectric (TE) application due to their high power factor (product of the square of the Seebeck coefficient and electrical conductivity). However, their high thermal conductivity is an issue of concern. Single doping has proven to be useful in improving TE performance in recent years. Here, it is shown that dual isovalent doping shows the synergistic effect of thermal conductivity reduction and electron density control. The insertion of large atoms in the layered Bi2Te3 structure distorts the crystal lattice and contributes significantly to phonon scattering. The ultralow thermal conductivity (KT = 0.35 W m−1 K−1 at 473 K) compensates for the low power factor and thus enhances TE performance. The density functional theory electronic structure calculation results reveal deep defects states in the valence band, which influences the electronic transport properties of the system. Therefore, the dual dopants (indium and antimony) show a coupled effect of improvement in the density of state near the Fermi level and reduction in the conduction band minimum, thus enhancing electron density. Numerically, it is demonstrated that the dual doping favors acoustic phonon scattering and thus drastically reduces the thermal conductivity.

Nowadays, air pollution has become a global menace being responsible of a significant increase on the morbidity and mortality of human beings. In view of this, sustainable and efficient technologies for air purification are being sought. Air purification by photocatalytic treatment has received a lot of attention due to the unspecific and high oxidation capacity of the catalyst; however still some variables must be optimized to assure practical applications. In this work, visible light active TiO2–Cu2+@perlite and Ag@TiO2–Cu2+/perlite supported materials were fabricated. TiO2–Cu2+ (2 at. %) were synthesized using a sol-gel procedure followed of the impregnation of the support by immersion. For Ag@TiO2–Cu2+, silver deposition was conducted by chemical reduction using sodium citrate and sodium borohydride. The materials (powders and supported materials) were characterized by Scanning Electron Microscopy (SEM) to demonstrate their small size and adherence to the substrate. A prototype of a photocatalytic air purifier was built. The efficacy of the prototype was evaluated for the disinfection of indoor air (dentistry clinics). The photo-catalyst was activated using visible and UVA low-cost high-energy LEDs. The antibacterial activity of the air filter was evaluated. Ag@TiO2–Cu2+ exerts better air disinfection activity at lower doses in comparison to TiO2–Cu2+. Bacterial growth inhibitions up to 99% were achieved for both, Gram-negative and Gram-positive bacteria. The incorporation of Ag and Cu to TiO2 improves the antibacterial activity of the materials due to enhanced photocatalytic activity and the synergic activity of TiO2 and dopant elements (Ag, Cu) to inhibit microorganism’s growth.

The availability of wide-band-gap oxides with bipolar conductivity is critical to developing transparent optoelectronic technologies. Unfortunately, most metal oxides show a strong propensity for $n$-type conductivity, while $p$-type doping remains extremely challenging. Focusing on CdO and NiO, which have type-III band offset, this study reveals that their alloy Ni${}_{x}$Cd${}_{1\ensuremath{-}x}$O${}_{1+\ensuremath{\delta}}$ can exhibit bipolar conductivity. Electronic band structure and native defects are manipulated by varying the oxygen stoichiometry. The results strongly suggest that these alloys have great technological potential for applications requiring transparent conducting oxides.