Design and tailoring of patterned ZnO nanostructures for perovskite light absorption modulation

Lithography is a pivotal micro/nanomanufacturing technique,facilitating performance enhancements in an extensive array of devices,encompassing sensors,transistors,and photovoltaic devices.The key to creating highly precise,multiscale-distributed patterned structures is the precise control of the lithography process.Herein,high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography.By optimizing these parameters,ZnO nanorod arrays with line/hole arrangements are successfully prepared.Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure,enlarged surface area,and improved light capture ability,which achieve highly efficient energy conversion in perovskite solar cells.The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.

Profile of Absolute Light Utilization Efficiency Within Leaves of Euonymus japonicus

Absolute light utilization efficiency across leaf section of Euonymus japonicus T. was calculated based on the measurements of photoacoustic technique (PA technique) and microscopic fiber optic probe. This new method was based on the principal of depth analysis by PA technique and the differential analysis of light gradients across leaf section by micro-optical probe technique. The depth analysis was shown by a sample of PA scan light absorption spectra. Results showed that the tissue layers between palisade tissue and spongy tissue used the smallest proportion of incident light energy for photochemical reactions (about 0.026% incident light energy of 660 nm light), while in tissue layer more close to the adaxial surface of leaf or the abaxial surface of leaf, the efficiency of utilization of light energy tended to be improved, e. g. 0.092% for tissue layers close to adaxial surface; 0.036% for tissue layers close to abaxial surface. The results that different leaf tissue layers utilized different proportion of incident light energy for photochemical reaction directly prove the hypothesis put forward by Han and Vogelmann.

Tip-induced directional charge separation on one-dimensional BiVO4 nanocones for asymmetric light absorption

One dimensional(1D)semiconductor is a class of extensively attractive materials for many emerging solar energy conversion technologies.However,it is still of shortage to assess the impact of 1D structural symmetry on spatial charge separation and understand its underlying mechanism.Here we take controllably-synthesized 1D BiVO_(4)nanocones and nanorods as prototypes to study the influence of 1D symmetry on charge separation.It is found that the asymmetric BiVO_(4)nanocones enable more effective charge separation compared with the symmetric nanorods.The unexpected spatial charge separation on the nanocones is mainly ascribed to uneven light absorption induced diffusion-controllable charge separation due to symmetry breaking of 1D nanostructure,as evidenced by spatial and temporal resolved spectroscopy.Moreover,the promotion effect of charge separation on the nanocones was quantitatively evaluated to be over 20 times higher than that in BiVO_(4)nanorods.This work gives the first demonstration of the influence of 1D structural symmetry on the charge separation behavior,providing new insights to design and fabricate semiconductor materials for efficient solar energy conversion.

Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods： The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results： The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using （tree- or stand-level） models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion： This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.

Laser-induced forward transferred silver nanomembrane with controllable light absorption

Laser processing provides highly-controlled modification and on-demand fabrication of plasmon metal nanostructures for light absorption and photothermal convention.We present the laser-induced forward tansfer(LIFT)fabrication of silver nanomembranes in control of light absorption.By varying the hatch distance,different morphologies of randomly distributed plasmon silver nanostructures were produced,leading to well-controlled light absorption levels from 11%to 81%over broadband.The anti-reflection features were maintained below 17%.Equilibrated and plain absorptions were obtained throughout all absorption levels with a maximum intensity fluctuation of±8.5%for the 225μJ cases.The 45μJ pulse energy can offer a highly equilibrated absorption at a 60%absorption level with an intensity fluctuation of±1%.Pattern transfer was also achieved on a thin tape surface.The laser-transferred characters and patterns demonstrate a localized temperature rise.A rapid temperature rising of roughly 15℃can be achieved within 1 s.The LIFT process is highly efficiently fabricated with a typical speed value of 10^(3)to 10^(5)cm^(2)/h.The results indicated that LIFT is a well-controlled and efficient method for the production of optical films with specific absorption levels.

Effect of Sm doping into CuInTe_(2) on cohesive energy before and after light absorption

The effects of Sm doping into CuInTe_(2) chalcopyrite on the cohesive energy before and after light absorption are systematically investigated by the empirical electron theory(EET) of solids and molecules.The results show that the static energy of CuIn_(1-x)Sm_(x)Te_(2) decreases with Sm content increasing due to the valence electronic structure modulated by doping Sm into CuIn_(1-x)Sm_(x)Te_(2).The calculated optical absorption transition energy from the static state to the excited energy level in CuIn_(1-x)Sm_(x)Te_(2) accords well with the experimental absorption bandgap of CuIn_(1-x)Sm_(x)Te_(2).Moreover,it is found that the energy bandgap of CuIn_(1-x)Sm_(x)Te_(2) is significantly widened with Sm content increasing due to its special valent electron structure,which is favorable for enhancing the light absorption in a wider range and also for the potential applications in solar cells.

Extreme Light Concentration and High Absorption of the Double Cylindrical Microcavities

We numerically study the enhancement factor of energy density and absorption efficiency inside the double cylindrical microcavities based on a triple-band metamaterial absorber. The compact single unit cell consists of concentric gold rings with a gold disk in the center and a metallic ground plane separated by a dielectric layer. We demonstrate that the multilayer structure with subwavelength electromagnetic confinement allows 104-105-fold enhancement of the electromagnetic energy density inside the double cavities and contains the most energy of the incoming light. Particularly, the enhancement factor of energy density G shows strong ability of localizing light and some regularity as the change of the thickness of the dielectric slab and dielectric constant. At the normal incidence of electromagnetic radiation, the obtained reflection spectra show that the resonance frequencies of the double microcavities operate in the range of 10-30μm. We also calculate the absorption efficiency C, which can reach 95%, 97% and 95% at corresponding frequency by optimizing the structure＇s geometry parameters. Moreover, the proposed structure will be insensitive to the polarization of the incident wave due to the symmetry of the double cylindrical microcavities. The proposed optical metamaterial is a promising candidate as absorbing elements in scientific and technical applications due to its extreme confinement, multiband absorption and polarization insensitivity.

Measurements of NO_2 mixing ratios with topographic target light scattering-differential optical absorption spectroscopy system and comparisons to point monitoring technique

A topographic target light scattering-differential optical absorption spectroscopy （＇IbTaL-DOA~） system is de- veloped for measuring average concentrations along a known optical path and studying surface-near distributions of atmospheric trace gases. The telescope of the ToTaL-DOAS system points to targets which are located at known dis- tances from the measurement device and illuminated by sunlight. Average concentrations with high spatial resolution can be retrieved by receiving sunlight reflected from the targets, A filed measurement of NO2 concentration is performed with the ToTaL-DOAS system in Shijiazhuang in the autumn of 2011. The measurement data are compared with con- centrations measured by the point monitoring technique at the same site. The results show that the ToTaL-DOAS system is sensitive to the variation of NO2 concentrations along the optical path.

Variability in the Light Absorption Coefficient by Phytoplankton,Non-Algal Particles and Colored Dissolved Organic Matter in the Northern Gulf of California

Variability of the optical properties of the northern Gulf of California (México) were analyzed for the first time based on six cruises performed from spring to summer (March to September) between 2008 and 2013. The changes observed in the absorption by three seawater components (phytoplankton, detritus and chromophoric dissolved organic matter or CDOM) were analyzed in relation to changes in bio-optical regions and composition of the phytoplankton community (determined based on phytoplankton pigments). Two regions with unique bio-optical characteristics were identified separated by a narrow transition zone: the Upper Gulf of California (UGC) and Northern Gulf of California (NGC). Despite the temporal changes in their spatial distribution they maintained particular characteristic. UGC is characterized by an average Chla of 1.78 mg/m3, the dominance of microphytoplankton (diatoms and dinoflagellates) and a stronger contribution of detritus to total light absorption. NGC is characterized by an average Chla of 0.7 mg/m3 and the predominance of picophytoplankton, characterized by the dominance of zeaxanthin (marker pigment for cyanobacteria) and/or chlorophyll b (marker pigment for green algae), along with a co-dominium by CDOM and phytoplankton to light absorption. Results indicate that Case II waters can be very different when evaluating the individual contribution by phytoplankton, detritus and CDOM to total light absorption what has to be considered for the selection of bio-optical models for each specific region what can also help to a better definition of the related uncertainties.

Dissolved organic carbon fractionation in wet deposition and its potential impact on radiative forcing in the central Tibetan Plateau

As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-centration and light absorption ability of precipitation DOC,affecting the climatic effect caused by DOC in the atmosphere.In this study,light absorption and fluorescence characteristics of precipitation DOC was investigated in the central Tibetan Plateau(TP).The results showed that the mean DOC concentration and mass absorption cross-section measured at 365 nm(MAC_(365)) in Tanggula(TGL)station were 0.59±0.42 mg/L and 0.37±0.19 m^(2)/g,respectively,while both values showed much higher volatilities than those of aerosols.DOC concentrations had significant negative correlation with the precipitation amount,while MAC_(365) values increase with the precipitation amount in TGL station.Therefore,DOC with high light-absorbing ability was preferred to be retained in the atmosphere during wet deposition.In this study,precipitation DOC contained three fluorescent components(one humic-like component and two tyrosine-like components)mainly from local biomass burning sources.DOC concentration showed a negative relationship with MAC_(365) value in TGL station.The wet deposition of DOC with low light-absorbing ability can reduce the strong negative radiative forcing caused by secondary organic aerosol due to high proportion of DOC in secondary organic carbon.Similar phenomenon was also found in Nam Co,Lulang and Everest stations of previous study,which may have a potential impact on radiative forcing in the atmosphere of TP.

Optimizing intrinsic cocatalyst activity and light absorption efficiency for efficient hydrogen evolution of 1D/2D ReS_(2)-CdS photocatalysts via control of ReS_(2)nanosheet layer growth

The visible-light-driven hydrogen evolution is extremely important,but the poor charge transfer capa-bility,a sluggish evolution rate of hydrogen,and severe photo-corrosion make photocatalytic hydrogen evolution impractical.In this study,we present 1D/2D ReS_(2)-CdS hybrid nanorods for photocatalytic hy-drogen evolution,comprised of a ReS_(2)nanosheet layer grown on CdS nanorods.We found that precise control of the contents of the ReS_(2)nanosheet layer allows for manipulating the electronic structure of Re in the ReS_(2)-CdS hybrid nanorods.The ReS_(2)-CdS hybrid nanorods with optimal ReS_(2)nanosheet layer content dramatically improve photocatalytic hydrogen evolution activity.Notably,photocatalytic hydro-gen evolution activity(64.93 mmol g^(−1)h^(−1))of ReS_(2)-CdS hybrid nanorods with ReS_(2)nanosheet layers(Re/Cd atomic ratio of 0.051)is approximately 136 times higher than that of pure CdS nanorods under visible light irradiation.Furthermore,intimated coupling of the ReS_(2)nanosheet layer with CdS nanorods reduced the surface trap-site of the CdS nanorods,resulting in enhanced photocatalytic stability.The de-tailed optical and electrical investigations demonstrate that the optimal ReS_(2)nanosheet layer contents in the ReS_(2)-CdS hybrid nanorods can provide improved charge transfer capability,catalytic activity,and light absorption efficiency.This study sheds light on the development of photocatalysts for highly efficient photocatalytic hydrogen evolution.

High-precision alkali-atom density measurement and control methods using light absorption for dual-beam SERF magnetometers

The alkali-atom density measurement method based on light absorption is highly suitable for a spin-exchange relaxationfree(SERF)atomic magnetometer because of its high-precision measurement and complete nonmagnetic interference.In this study,the optical rotation angle detection system based on polarization balance detection is utilized to realize the alkali-atom density real-time measurement without affecting magnetic field measurement.We discovered that there exists an optimal frequency detuning of the probe light,which offers the highest sensitivity in alkali-atom density measurement and the lowest susceptibility to temperature fluctuations in terms of the scale factor.In contrast to conventional light absorption measurements based on pump light,this method demonstrated a threefold improvement in alkali-atom density measurement sensitivity while remaining immune to ambient magnetic fields and incident light intensity fluctuations.Furthermore,we utilized this method to achieve closed-loop temperature control with an accuracy of 0.04℃.

Dual-symmetry-perturbed all-dielectric resonant metasurfaces for high-Q perfect light absorption

We demonstrate a high-Q perfect light absorber based on all-dielectric doubly-resonant metasurface.Leveraging bound states in the continuum(BICs)protected by different symmetries,we manage to independently manipulate the Q factors of the two degenerate quasi-BICs through dual-symmetry perturbations,achieving precise matching of the radiative and nonradiative Q factors for degenerate critical coupling.We achieve a narrowband light absorption with a>600 Q factor and a>99%absorptance atλ_(0)=1550 nm on an asymmetric germanium metasurface with a 0.2λ_(0)thickness.Our work provides a new strategy for engineering multiresonant metasurfaces for narrowband light absorption and nonlinear applications.

Preparation of Nano-TiO_2 Doped with Cerium and Its Photocatalytic Activity

Cerium-doped titanium dioxide nano-powders were prepared through the sol-gel method and the compound sampies were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and UV/Vis diffuse reflectance spectra （DRS）. The photocatalytic activity was evaluated by photocatalytic degradation of phenol in water. The results of XRD, TEM, and DRS show that pure TiO2 and Ce-doped TiO2 powder crystallines are a mixture of anatase and rutile ; the doping can retard the development of the grain size of TiO2 and decrease the diameter of TiO2 from more than 20 nm of pure TiO2 to about 10 nm; the doped TiO2 can improve the light absorption of TiO2 and suitable doping content tends to move the DRS spectrum of TiO2 towards visible light, but too much doping is not good for the light absorption ability. The results of the photocatalytic experiments show that doping with Ce content of 0.08% -0.4% can increase the photocatalytic activity of TiO2; however, doping with Ce content of 0.5% -2.5% can significantly decrease the photocatalytic activity of TiO2. The favorite doping content is 0.4% in the range of our experiments.

The embedded CuInS2 into hollow-concave carbon nitride for photocatalytic H2O splitting into H2 with S-scheme principle

It is still a great challenge to effectively optimize the electronic structure of photocatalysts for the sustainable and efficient conversion of solar energy to H2 energy.To resolve this issue,we report on the optimization of the electronic structure of hollow-concave carbon nitride(C3N4)by deviating the sp2-hybridized structure of its tri-s-triazine component from the two-dimensional plane.The embedded CuInS2 into C3N4(CuInS2@C3N4)demonstrates an increased light-capturing capability and the promoted directional transfer of the charge carrier.Research results reveal that the hollow structure with an apparent potential difference between the concave and convex C3N4 drives the directional transfer of the photoinduced electrons from the Cu 2p orbital of CuInS2 to the N 1s orbital of C3N4 with the S-scheme principle.The H2 evolution efficiency over CuInS2@C3N4 is up to 373μmol?h^-1 g^-1 under visible irradiation,which is 1.57 and 1.35 times higher than those over the bulk g-C3N4 with 1 wt%Pt(238μmol?h^-1 g^-1)and g-C3N4 with 3 wt%Pd(276μmol?h^-1 g^-1),respectively.This suggests that the apparent potential difference of the hollow C3N4 results in an efficient reaction between the photogenerated electrons and H2O.This work supplies a new strategy for enhancing the sustainable solar conversion performance of carbon nitride,which can also be suitable for other semiconductors.

Pyrolysis of Rice Husk in a Fluidized Bed Reactor:Evaluate the Characteristics of Fractional Bio-Oil and Particulate Emission of Carbonaceous Aerosol(CA)

Bio-oil production via pyrolysis is one of promising technologies for renewable energy production from bio-wastes.However,the complicated biooil is still a challenge for high-valued application and during biomass pyrolysis,the emission of non-cleaned aerosol,the potential emission,namely carbonaceous aerosol(CA)increased the difficulty of the commercial promotion.In this study,Rice husk pyrolysis was performed in a semi-continuous fluidized bed reactor coupled with fractional condensers.The effects of pyrolysis and condensation temperature on the properties of bio-oil and emission of CAwere investigated systemically.Results indicated that the in-situ separation of vapors was accomplished via condensers of different temperatures(85℃and−10℃).The bio-oil with different physiochemical properties were obtained in the high content of phenols and lower acids of BO1 and high content of acids and better liquidity.The size distribution of CA was found primarily classified as sub-micrometer grade particles,which have a diameter of less than 1.1μm.In particular,CA existed in three representative forms:bead,granular aggregate,and liquidoid.The results of light absorption of total organic carbon(TOC)and non-volatile organic carbon(NVOC)indicated that the absorption per mass increased in the single temperature with the decrement of wavelength and it improved as the pyrolysis temperature increased at the specified wavelength.The absorption per mass was to maximum value(3.7 m^(2)/g)at 360 nm wavelength and 600℃.TOC demonstrated a strong light absorption and a wide spectral range dependence(AAE:5.08-10.05)which enhanced the light absorption in the ultra-violet and low-visible regions.

Ultra-Thin Carbon-Doped Bi_(2)WO_(6) Nanosheets for Enhanced Photocatalytic CO_(2) Reduction

The photocatalytic reduction of CO_(2) is a promising strategy to generate chemical fuels.However,this reaction usually suf-fers from low photoactivity because of insuffi cient light absorption and rapid charge recombination.Defect engineering has become an eff ective approach to improve the photocatalytic activity.Herein,ultra-thin(~4.1 nm)carbon-doped Bi_(2)WO_(6) nanosheets were prepared via hydrothermal treatment followed by calcination.The ultra-thin nanosheet structure of the cata-lyst not only provides more active sites but also shortens the diff usion distance of charge carriers,thereby suppressing charge recombination.Moreover,carbon doping could successfully extend the light absorption range of the catalyst and remarkably promote charge separation,thus inhibiting recombination.As a result,the as-prepared Bi_(2)WO_(6) photocatalyst with ultra-thin nanosheet structure and carbon doping exhibits enhanced photocatalytic CO_(2) reduction performance,which is twice that of pristine ultra-thin Bi_(2)WO_(6) nanosheet.This study highlights the importance of defect engineering in photocatalytic energy conversion and provides new insights for fabricating effi cient photocatalysts.

Integrated Photothermal Nanoreactors for Effi cient Hydrogenation of CO_(2)

To alleviate the energy crisis and global warming,photothermal catalysis is an attractive way to effi ciently convert CO_(2)and renewable H_(2) into value-added fuels and chemicals.However,the catalytic performance is usually restricted by the trade-off between the dispersity and light absorption property of metal catalysts.Here we demonstrate a simple SiO 2-protected metal-organic framework pyrolysis strategy to fabricate a new type of integrated photothermal nanoreactor with a comparatively high metal loading,dispersity,and stability.The core-satellite structured Co@SiO_(2)exhibits strong sunlight-absorptive abil-ity and excellent catalytic activity in CO_(2)hydrogenation,which is ascribed to the functional separation of diff erent sizes of Co nanoparticles.Large-sized plasmonic Co nanoparticles are mainly responsible for the light absorption and conversion to heat(nanoheaters),whereas small-sized Co nanoparticles with high intrinsic activities are responsible for the catalysis(nanoreactors).This study provides a new concept for designing effi cient photothermal catalytic materials.

Electronic, Thermal Expanding, and Optical Absorption Properties of Transition Metal Dichalcogenides: A First-principles Study

A comprehensive investigation was made on the electronic structure, thermal expansion coefficient and light absorption spectrum of total six transition metal dichalcogenides(TMDs) compounds with formula of MX_2(M=Mo, W, Cr, X=S, Se). First, an indirect-direct band gap transition from bulk to singlelayer was declared for all the six compounds. Moreover, the detailed lattice constants and thermal expansion coefficients provided in the paper were the key information for designing MX_2-based field effect transistors. Finally, the calculated optical absorption spectra demonstrate that these compounds can effectively utilize solar energy and are good photo catalyst candidates. All these present findings will benefit the design of new generation of novel two-dimensional materials.

Preparation and UV property of size-controlled monodisperse nickel nanoparticles (<10 nm) by reductive method

Nickel nanoparticles （〈10 nm） were success fully synthesized using a reductive method of nickel chloride with sodium borohydride in the ethanol/poly vinylpyrrolidone （PVP） system. The effects of three fac tors, such as the concentration of the nickel ions, the time of reaction, and the amount of PVP （surfactant）, were discussed. The possible growth process of the particles and optimum reactive conditions was also investigated. The result of transmission electron microscopy （TEM） reveals that these nickel nanoparticles are spherical. The average diameter could be controlled as 25 nm under selected conditions. Highresolution TEM and energydispersive spectroscopy results indicates that the nickel nanoparticles are pure. The UVvisible light absorption spectrum shows that the peaks of nickel nanoparticles moves toward the short wavelength along with the decrease of sizes.