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Crystallographic defects are essential to the functional properties of semiconductors, controlling everything from conductivity to optical properties and catalytic activity. In nanocrystals, too, defect engineering with extrinsic dopants has been fruitful. Although intrinsic defects like vacancies can be equally useful, synthetic strategies for controlling their generation are comparatively underdeveloped. Here, we show that intrinsic defect concentration can be tuned during the synthesis of colloidal metal oxide nanocrystals by the addition of metal salts. Although not incorporated in the nanocrystals, the metal salts dissociate at high temperatures, promoting the dissociation of carboxylate ligands from metal precursors, leading to the introduction of oxygen vacancies. For example, the concentration of oxygen vacancies can be controlled up to 9% in indium oxide nanocrystals. This method is broadly applicable as we demonstrate by generating intrinsic defects in metal oxide nanocrystals of various morphologies and compositions.

This study describes nanocomposites of graphene flakes (GF) combined with CuS, Fe3O4 and CuS−Fe3O4 nanoparticles prepared by wet chemical methods. The Fe3O4 and/or CuS nanoparticles were directly anchored onto GF without requiring additional chemical treatment. The composition, structure and morphology of the nanocomposites, as well as of the pristine GF and metal oxide/sulfide nanoparticles were characterised by X − ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), powder X − ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results confirmed the successful attachment of CuS nanophases (size range: 23.7–50.1 nm) and/or Fe3O4 nanoparticles (size range: 10.6–15.8 nm). The adsorption and photocatalytic properties of the GF−based nanocomposites were evaluated at room temperature using Rhodamine B (RhB) as a model contaminant. Theoretical models were fitted to the adsorption kinetic results using the pseudo-first-order, pseudo-second-order and Elovich equations, while the adsorption mechanism was determined using the intraparticle diffusion, Bangham and Boyd models. The RhB adsorption efficiency was 6.5% for GF@CuS−Fe3O4 after 180 min contact time, whereas for the other materials was significantly higher: 97.6%, 60.9% and 31.9% for GF, GF@CuS and GF@Fe3O4, respectively. The adsorption capacity of GF and composites fitted the pseudo−second−order kinetic and Elovich models. The influence of the nanostructures composition on the corresponding photocatalytic activity in the degradation of RhB under a 150 W halogen lamp was also evaluated. The GF@CuS−Fe3O4 nanocomposite totally eliminated the dissolved RhB after 60 min irradiation, whereas the GF@CuS, GF@Fe3O4 and pristine Fe3O4 removed 75.6%, 80.9% and 30.8%, respectively, after 180 min irradiation. It was found that the photocatalytic behaviour of the composites was best described by the first−order kinetic model. The rate constant of the photocatalytic RhB removal for GF@CuS−Fe3O4 (k = 7.05 ×10−2 min−1) was 2.1, 5.1 and 15.0 times higher than those obtained for GF@CuS, GF@Fe3O4 and pristine Fe3O4, respectively, after 60 min of visible light irradiation. published

CuInSe2 nanocrystals exhibit tunable near-infrared bandgaps that bolster utility in photovoltaic applications as well as offer potential as substitutes for more toxic Cd- and Pb-based semiconductor...

Grazing incidence small angle X-ray scattering (GISAXS) was used to study the structure and interparticle spacing of monolayers of organic ligand-stabilized iron oxide nanocrystals floating at the air-water interface on a Langmuir trough, and after transfer to a solid support by the Langmuir-Blodgett technique. GISAXS measurements of the nanocrystal arrangement at the air-water interface showed that lateral compression decreased the interparticle spacing of continuous films. GISAXS also revealed that Langmuir-Blodgett transfer of the nanocrystal layers to a silicon substrate leads to a stretching of the film, with a significant increase in interparticle spacing.

Electrochemical conditioning via chronopotentiometry (CP) and cyclic voltammetry (CV) is essential for the activation of oxygen evolution reaction (OER) electrocatalysts. While many reports have activated OER electrocatalysts using either CP or CV, the inherent differences between these two electrochemical conditioning methods for the activation of OER electrocatalytic materials have yet to be explored. Here, we investigate the effects of CP and CV electrochemical conditioning on a Ni-based OER precatalyst and substrate in Fe-purified and Fe-unpurified KOH electrolytes by employing (ⅰ) Ni foil, (ⅱ) NiSe precatalyst films with different thicknesses on the fluorine-doped tin oxide glass substrate, and (ⅲ) NiSe precatalyst films on Ni foil substrates. It was found that CV electrochemical conditioning can result in a higher degree of in situ oxidation and Fe incorporation for Ni-based precatalysts and substrates compared to CP electrochemical conditioning. In turn, this brought about different material properties (e.g., in situ oxidized layer thickness, composition, crystallinity, and morphology) and electrochemical characteristics (e.g., active surface area, electron transport limitation, and intrinsic activity) of Ni-based electrocatalysts, thereby not only affecting their OER activity but also complicating the interpretation of the origin of OER activity. This study identifies the distinct effects of CP and CV electrochemical conditioning on Ni-based OER electrocatalysts and provides insight into the choice of the electrochemical conditioning method to better investigate OER electrocatalysts.

CuInSe2 nanocrystals offer promise for optoelectronics including thin-film photovoltaics and printed electronics. Additive manufacturing methods such as photonic curing controllably sinter particle...

A wide range of material properties can be accessed by tuning the size and shape of nanocrystals (NCs). Cations incorporated into the crystal lattice of indium oxide (In2O3) NCs as dopants have bee...

Metal halide perovskite nanocrystals offer a range of interesting properties and are being studied extensively for applications in solar cells, photodetectors and light-emitting devices. This persp...

Coloration efficiency is an important figure of merit in electrochromic windows. Though it is thought to be an intrinsic material property, we tune optical modulation by effective utilization of ion intercalation sites. Specifically, we enhance the coloration efficiency of m-WO

The homogeneous exciton linewidth, which captures the coherent quantum dynamics of an excitonic state, is a vital parameter in exploring light-matter interactions in two-dimensional transition metal dichalcogenides (TMDs). An efficient control of the exciton linewidth is of great significance, and in particular of its intrinsic linewidth, which determines the minimum timescale for the coherent manipulation of excitons. However, such a control has rarely been achieved in TMDs at room temperature (RT). While the intrinsic A exciton linewidth is down to 7 meV in monolayer WS(2), the reported RT linewidth was typically a few tens of meV due to inevitable homogeneous and inhomogeneous broadening effects. Here, we show that a 7.18 meV near-intrinsic linewidth can be observed at RT when monolayer WS(2) is coupled with a moderate-refractive-index hydrogenated silicon nanosphere in water. By boosting the dynamic competition between exciton and trion decay channels in WS(2) through the nanosphere-supported Mie resonances, we have managed to tune the coherent linewidth from 35 down to 7.18 meV. Such modulation of exciton linewidth and its associated mechanism are robust even in presence of defects, easing the sample quality requirement and providing new opportunities for TMD-based nanophotonics and optoelectronics.

CuInSe

As editors of a materials chemistry journal, we are thrilled at the awarding of the 2019 Nobel Prize in Chemistry to John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino, for their contributions that have led to the modern lithium ion battery (Figure 1). As the Nobel Prize Committee states succinctly, “They created a rechargeable world.”(1) The commercial and societal rewards of experimental research typically require decades to reach fruition, and lithium ion batteries were no different, with crucial leads dating back to the 1960s, and even earlier.(2) Materials chemistry journals only emerged 30 years ago with the advent of Chemistry of Materials, the Journal of Materials Chemistry, and Advanced Materials in 1989. Much of the earlier work in battery materials appeared beforehand in electrochemistry, physics, and solid state journals. The key fundamental discovery underpinning the lithium ion battery was the understanding and application of ion intercalation, in this case,(3) lithium ions inserted between the layers in graphite, metal sulfides, and, eventually, oxides that were commercialized. This Nobel Prize was evenly split three ways because, as the Nobel committee correctly observed, the contributions of all three inventors were essential to the success of the commercialization of the lithium ion battery.

The equilibrium phase of cesium lead iodide (CsPbI3) at room temperature is yellow and optically inactive due to its indirect band gap. The metastable black phase of CsPbI3 on the other hand exhibi...

Capping ligand bonding and the thermal and colloidal stability of Cs2AgBiBr6 nanocrystals were studied. Oleylamine and oleic acid bonding to Cs2AgBiBr6 nanocrystals was studied with 1H nuclear magn...

There has been significant interest in I–III–VI2 nanocrystals for photonic and optoelectronic applications, especially solar cells. CuInSe2 nanocrystals have been studied extensively as model materials for this class of compounds. By incorporation of Ga to make CuInxGa1–xSe2 (CIGSe), the optical gap can be tuned by composition as well as size for higher efficiency solar cells or other applications. The synthesis of CIGSe nanocrystals, however, has not been studied in much detail. It turns out that the addition of Ga to the typical arrested precipitation reactions for CuInSe2 nanocrystals in oleylamine (OLAm) leads to very slow particle nucleation and growth rates. In order to achieve consistent morphology, reaction yield, and Ga incorporation, a lengthy (∼24 h) low temperature incubation step is needed. Under these slow growth conditions, the crystal structure of the CIGSe nanocrystals is cubic. By addition of diphenylphosphine (DPP) to the reactions, the nucleation and growth rates are significantly incr...

Inorganic single crystals with anisotropic structures usually suffer from high brittleness and stiffness. Flexible polymers are used to replace inorganic crystals, but the hot-stretching-induced orientation process is tedious, and oriented molecular chains tend to revert to random coils during aging. To overcome these obstacles and using the similarities between sub-1 nm nanowires (NWs) and linear polymers, we successfully fabricated anisotropic, transparent, flexible, and stable (ATFS) NW films with great potential for optical applications through a wet-spinning method. The NW films show birefringence, and their birefractive index is higher than that of many polymers. They also showed polarized absorption of UV light and anisotropic scattering of visible light. The integrated films composed of NWs and quantum dots showed good fluorescence polarization. The tedious synthesis of quantum rods and fabrication of oriented polymer films can thus be avoided.

Colloidal nanocrystals of CH3NH3PbI3 (MAPI) with the tetragonal crystal structure and cuboidal shape terminated by {110} and {002} facets were assembled into superlattices with cubatic structure an...

Copper indium diselenide (CuInSe2) is a prototype ternary compound and group I–III–VI semiconductor with useful optoelectronic properties. CuInSe2 nanocrystals have been of significant interest because of their size-tunable optical properties and lack of toxic heavy metals. Because of the particular vacancy and antisite substitutional point defects in CuInSe2, large stoichiometric deviations can be tolerated, sometimes leading to the so-called ordered vacancy compounds (OVCs). Here, we use Raman spectroscopy of oleylamine-capped CuInSe2 nanocrystals and ab initio lattice dynamics modeling to study the concentration and arrangements of (2vCu– + InCu2+) defect pairs in the nanocrystals. The nanocrystals have randomly distributed defect pairs that become mobile under light excitation and accumulate, as in OVCs, along the [100] direction. Because the high concentration of vacancies in CuInSe2 nanocrystals is compensated by InCu2+ antisite defects, these nanocrystals do not exhibit an optical plasmon resonance...

Nanocrystal inks have been used to make printed photovoltaic devices (PVs) with reasonably high efficiencies; however, little is actually known about the material properties that limit the performance of these devices. Here, we model the output characteristics of PVs with CuInSe2 nanocrystal absorber layers using the Solar Cell Capacitance Simulator (SCAPS) software package and obtain the thickness-limited response and typical current–voltage behavior, power conversion efficiency (PCE), and external quantum efficiency (EQE) of experimentally fabricated PVs. The device behavior is accurately modeled using a low carrier mobility of 5 × 10–4 cm2 V–1 s–1 and measured optical properties for the CuInSe2 nanocrystal films. The simulations reveal that a reduction in the energy barrier for hole transport at the back contact and increased mobility and lifetime of charge carriers in the CuInSe2 nanocrystal layer could improve device performance. Furthermore, this system is qualitatively different than the well-studi...

Coupling emitters with nanoresonators is an effective strategy to control light emission at the subwavelength scale with high efficiency. Low-loss dielectric nanoantennas hold particular promise for this purpose, owing to their strong Mie resonances. Herein, we explore a highly miniaturized platform for the control of emission based on individual subwavelength Si nanospheres (SiNSs) to modulate the directional excitation and exciton emission of two-dimensional transition metal dichalcogenides (2D TMDs). A modified Mie theory for dipole-sphere hybrid systems is derived to instruct the optimal design for desirable modulation performance. Controllable forward-to-backward intensity ratios are experimentally validated in 532 nm laser excitation and 635 nm exciton emission from a monolayer WS(2). Versatile light emission control is achieved for different emitters and excitation wavelengths, benefiting from the facile size control and isotropic shape of SiNSs. Simultaneous modulation of excitation and emission via a single SiNS at visible wavelengths significantly improves the efficiency and directionality of TMD exciton emission and leads to the potential of multifunctional integrated photonics. Overall, our work opens promising opportunities for nanophotonics and polaritonic systems, enabling efficient manipulation, enhancement and reconfigurability of light-matter interactions.

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research. Ministerio de Ciencia e Innovación | Ref. RYC2018-026103-I Agencia Estatal de Investigación | Ref. CTQ2017-82711-P Ministerio de Economía y Competitividad | Ref. MDM-2015-0538 Agencia Estatal de Investigación | Ref. PID2019-107314RB-I00

International audience; A goal in the field of nanoscale optics is the fabrication of nanostructures with strong directional light scattering at visible frequencies. Here, we demonstrate the synthesis of Mie-resonant coreshell particles with overlapping electric and magnetic dipole resonances in the visible spectrum. The core consists of silicon surrounded by a lower index silicon oxynitride (SiOxNy) shell with an adjustable thickness. Optical spectroscopies coupled to Mie theory calculations give the first experimental evidence that the relative position and intensity of the magnetic and electric dipole resonances are tuned by changing the core-shell architecture. Specifically, coating a high-index particle with a low-index shell coalesces the dipoles, while maintaining a high scattering efficiency, thus generating broadband forward scattering. This synthetic strategy opens a route towards metamaterial fabrication with unprecedented control over visible light manipulation.

Subwavelength nanostructures with tunable compositions and geometries show favorable optical functionalities for the implementation of nanophotonic systems. Precise and versatile control of structural configurations on solid substrates is essential for their applications in on-chip devices. Here, we report all-solid-phase reconfigurable chiral nanostructures with silicon nanoparticles and nanowires as the building blocks in which the configuration and chiroptical response can be tailored on-demand by dynamic manipulation of the silicon nanoparticle. We reveal that the optical chirality originates from the handedness-dependent coupling between optical resonances of the silicon nanoparticle and the silicon nanowire via numerical simulations and coupled-mode theory analysis. Furthermore, the coexisting electric and magnetic resonances support strong enhancement of optical near-field chirality, which enables label-free enantiodiscrimination of biomolecules in single nanostructures. Our results not only provide insight into the design of functional high-index materials but also bring new strategies to develop adaptive devices for photonic and electronic applications.

CuInSe

Colloidal synthesis is harnessed for the gram-scale preparation of hexagonal-shaped plate-like Bi

Optomechanics arises from the photon momentum and its exchange with low-dimensional objects. It is well known that optical radiation exerts pressure on objects, pushing them along the light path. However, optical pulling of an object against the light path is still a counter-intuitive phenomenon. Herein, we present a general concept of optical pulling—opto-thermoelectric pulling (OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path. This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles, and three-dimensional (3D) trapping of single particles is achieved at an extremely low optical intensity of 10−2 mW μm−2. Moreover, the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance. The concept of self-induced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-a-chip devices., Optical pulling: Light can move particles against the stream In a phenomenon termed opto-thermoelectric pulling (OTEP), the optical heating of a particle due to the absorption of a simple plane light wave can pull the particle against the direction of the light path. Linhan Lin, Yuebing Zheng and colleagues at the University of Texas at Austin, USA, demonstrate this counter-intuitive concept by manipulating particles of silicon 500 namometers across. The authors propose a mechanism allowing the effect of optical heating to oppose and overcome the optical force in the direction of the light beam. They explain how this can be achieved by manipulating the interaction of the energy of photons with the target particles. The phenomenon can trap and move particles using extremely low optical intensities. There are potential applications based on the interaction of light with fluids (optofluidics) especially in lab-on-a-chip devices.

A synthetic challenge in faceted metal oxide nanocrystals (NCs) is realizing tunable localized surface plasmon resonance (LSPR) near-field response in the infrared (IR). Cube-shaped nanoparticles of noble metals exhibit LSPR spectral tunability limited to visible spectral range. Here, we describe the colloidal synthesis of fluorine, tin codoped indium oxide (F,Sn:In

Colloidal synthesis is harnessed for the gram-scale preparation of hexagonal-shaped plate-like Bi2Te2.7Se0.3 particles, yielding nearly 5 g of the product in one experiment. The resultant textured particles are highly crystalline, phase-pure, chemically uniform, and can serve as a starting material for the preparation of bulk thermoelectrics for room temperature applications. The consolidation occurs via spark plasma sintering, which affords nanostructured n-type Bi2Te2.7Se0.3 material exhibiting a high figure of merit ZT ≈ 1 at 373 K with an average ZT ≈ 0.93 (300-473 K). Our experimental and theoretical studies indicate that the high thermoelectric performance is attributed to a favorable combination of the resultant transport properties. Specifically, bottom-up formation of the plate-like particles results in the substantial reduction of thermal conductivity by nanostructuring as observed experimentally and can be ascribed to phonon scattering at grain boundaries and suppressed bipolar conduction. When coupled with high electrical conductivity, which is preserved at the bulk scale as confirmed by ab initio calculations, these factors boost the thermoelectric performance of the as-synthesized n-type Bi2Te2.7Se0.3 bulk nanostructured alloy to the state-of-the-art level. The combination of a newly developed scalable colloidal synthesis with optimized spark plasma sintering constitutes a convenient route to nanostructured bulk thermoelectrics, which is an interesting pathway for the preparation of simple and complex thermoelectric chalcogenides., This work was supported by Portuguese National Funding Agency for Science, Research and Technology (FCT) under the UT-BORN-PT project (UTAP-EXPL/CTE/0050/2017). B. A. K. acknowledges funding of this work by the Robert A. Welch Foundation (grant no. F-1464).

A novel nanocomposite based on molecularly imprinted polymer (MIP) polymerized over silica nanoparticles (Si) is used for the development of an all-solid-state (ASS) potentiometric sensor for determination of sarcosine, a biomarker for Prostate Cancer (PCa). This MIP-Si sensor has shown high selectivity in phosphate-buffered solution (PBS) and simulated body fluid (SBF). We have obtained a linear response (10−5–10−8 mol/L), with a low detection limit (7.8 × 10−8 mol/L) and a quick response time close to 30 s, being stable for at least 150 days. It is corroborated that the sensor is a stable, reproducible, and sensitive biosensing device for PCa detection.

Methylammonium lead iodide (CH3NH3PbI3, MAPI) is a high-performance solar cell material but lacks stability in the presence of humidity. Addition of a few percent bismuth (Bi) as a trivalent cation substitute for Pb (i.e., MAP(Bi)I) leads to enhanced stability under high (90%) relative humidity (RH). At moderate humidity (60% RH), however, MAP(Bi)I degrades more rapidly than MAPI. Bi incorporation into MAPI either stabilizes or destabilizes the two hydration products, MAPI·H2O and PbI2, depending on the amount of humidity in the environment.

Copper indium diselenide (CuInSe2) nanocrystals are a prototypical I–III–VI semiconductor quantum dot material, typically synthesized in oleylamine (OLAm) as a solvent and capping ligand, often with the addition of diphenylphosphine (DPP) to improve the reaction yield. Using 1H nuclear magnetic resonance spectroscopy, we study the association of OLAm and DPP on CuInSe2 nanocrystals and find that they both behave as tightly bonded L-type ligands. There is no observable desorption of OLAm or DPP when a toluene-d8 dispersion is heated to 100 °C, and no ligand exchange occurs when the nanocrystals are exposed to other L-type species like trioctylphosphine (TOP) or octadecanethiol (ODT), which can bind as either X-type or L-type. Molecular iodine (I2), however, is found to readily displace both OLAm and DPP from the nanocrystal surface and facilitate efficient and complete ligand exchange with either TOP or ODT and appears to behave as a Lewis acid Z-type ligand. We also find that the X-type ligand, stearic ac...

Silicon (Si) nanowires with a silicon oxide (SiOx) shell undergoing lithiation and delithiation were examined by in situ transmission electron microscopy (TEM). Large pores formed in the nanowires during the delithiation cycle. We found that the oxide shell constrains the expansion of the Si nanowires during lithitation and then induces pore formation in the nanowires. We propose that the SiOx shell prevents the vacancies that result from the loss of lithium from escaping the Si core, leading to pore nucleation and growth. It is also possible that the difference in mechanical properties of the expanding and contracting Si nanowire and SiOx shell contribute to the observed pore formation. This in situ study reaffirms the need to directly observe structural changes that occur during cycling in battery materials, especially when modified by coatings.

Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) are extremely attractive materials for optoelectronic applications in the visible and near-infrared range. Coupling these materials to optical nanocavities enables advanced quantum optics and nanophotonic devices. Here, we address the issue of resonance coupling in hybrid exciton–polariton structures based on single Si nanoparticles (NPs) coupled to monolayer (1L)-WS2. We predict a strong coupling regime with a Rabi splitting energy exceeding 110 meV for a Si NP covered by 1L-WS2 at the magnetic optical Mie resonance because of the symmetry of the mode. Further, we achieve a large enhancement in the Rabi splitting energy up to 208 meV by changing the surrounding dielectric material from air to water. The prediction is based on the experimental estimation of TMDC dipole moment variation obtained from the measured photoluminescence spectra of 1L-WS2 in different solvents. An ability of such a system to tune the resonance coupling is rea...

Colloidal nanorods with axial Si and Ge heterojunction segments were produced by solution-liquid-solid (SLS) growth using Sn as a seed metal and trisilane and diphenylgermane as Si and Ge reactants. The low solubility of Si and Ge in Sn helps to generate abrupt Si-Ge heterojunction interfaces. To control the composition of the nanorods, it was also necessary to limit an undesired side reaction between the Ge reaction byproduct tetraphenylgermane and trisilane. High-resolution transmission electron microscopy reveals that the Si-Ge interfaces are epitaxial, which gives rise to a significant amount of bond strain resulting in interfacial misfit dislocations that nucleate stacking faults in the nanorods.

Photoluminescence (PL) spectra were measured for dodecene-capped Si nanocrystals with a wide range of average diameters, from 1.8 to 9.1 nm. Nanocrystals larger than 3 nm exhibited relatively high PL quantum yields of 30%−45%. Smaller nanocrystals exhibited lower quantum yields that decreased significantly with reduced size. Because smaller nanocrystals also have lower optical absorption there is a significant biasing of the PL spectra by the larger nanocrystals. We show that with proper accounting of polydispersity and size- dependent quantum yields and optical absorption the effective mass approximation (EMA) accurately estimates the average diameter of silicon (Si) nanocrystals from experimentally determined PL emission peak energies. A finite confinement model is presented that explains the decreased PL quantum yields of the smaller diameter nanocrystals.

Colloidal silica nanoparticles with average diameters less than 100 nm were made using a modified Stober method involving tetraethylorthosilicate (TEOS) and octadecyl trimethoxysilane (OTMOS) as a surface modifier. We show that the hydrophobicity of the nanoparticles could be tuned in this one-step reaction by introducing methanol as a co-solvent with ethanol and optimizing the ammonium hydroxide concentration and time elapsed between TEOS and OTMOS addition. Using this approach, silica nanoparticles could be made directly with the proper surface hydrophobicity to stabilize invert (water-in-oil) emulsions with shear-thinning rheological behavior as needed in oil drilling applications. Particle characterization data from transmission and scanning electron microscopy (TEM and SEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), and contact angle measurements are presented.

Solar cells on paper have the potential to be inexpensive and portable due to several unique features of the substrate: paper is cheap, flexible, lightweight, biodegradable, and manufactured by roll-to-roll processing. Here, we report the first nanocrystal photovoltaic devices (PVs) made on paper. Using spray-deposited CuInSe2 nanocrystals as the absorber material on substrates composed of bacterial cellulose nanofibers synthesized by the microorganism Gluconacetobacter hansenii, these devices demonstrate exceptional electrical and mechanical integrity. There is no significant loss in PV device performance after more than 100 flexes to 5 mm radius, and the devices continue to perform when folded into a crease. The practical use of these paper PVs is demonstrated with a prototype device powering liquid crystal displays (LCDs) mounted to various kinds of surfaces.

Constructing colloidal particles into functional nanostructures, materials, and devices is a promising yet challenging direction. Many optical techniques have been developed to trap, manipulate, assemble, and print colloidal particles from aqueous solutions into desired configurations on solid substrates. However, these techniques operated in liquid environments generally suffer from pattern collapses, Brownian motion, and challenges that come with reconfigurable assembly. Here, we develop an all-optical technique, termed optothermally-gated photon nudging (OPN), for the versatile manipulation and dynamic patterning of a variety of colloidal particles on a solid substrate at nanoscale accuracy. OPN takes advantage of a thin surfactant layer to optothermally modulate the particle-substrate interaction, which enables the manipulation of colloidal particles on solid substrates with optical scattering force. Along with in situ optical spectroscopy, our non-invasive and contactless nanomanipulation technique will find various applications in nanofabrication, nanophotonics, nanoelectronics, and colloidal sciences., Particle manipulation is still challenging even with the many tools available, especially manipulating particles on a surface. Here, the authors report a technique for nanomanipulation of various objects on solid substrates by modulating particle-substrate interactions through laser-induced opto-thermal dynamics.