Light Path Length Research Articles

Monitoring shipping emissions in the German Bight using MAX-DOAS measurements

Abstract. A 3-year time series of ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of NO2 and SO2 on the island Neuwerk has been analyzed for contributions from shipping emissions. The island is located in the German Bight, close to the main shipping lane (at a distance of 6–7 km) into the river Elbe towards the harbor of Hamburg. Measurements of individual ship plumes as well as of background pollution are possible from this location. A simple approach using the column amounts of the oxygen molecule dimer or collision complex, O4, for the determination of the horizontal light path length has been applied to retrieve path-averaged volume mixing ratios. An excellent agreement between mixing ratios determined from NO2 retrievals in the UV and visible parts of the spectrum has been found, showing the validity of the approach. Obtained mixing ratios of NO2 and SO2 are compared to co-located in situ measurements showing good correlation on average but also a systematic underestimation by the MAX-DOAS O4 scaling approach. Comparing data before and after the introduction of stricter fuel sulfur content limits (from 1 to 0.1 %) on 1 January 2015 in the North Sea Emission Control Area (ECA), a significant reduction in SO2 levels is observed. For situations with wind from the open North Sea, where ships are the only local source of air pollution, the average mixing ratio of SO2 decreased by a factor of 8, while for NO2 in the whole time series from 2013 to 2016, no significant change in emissions was observed. More than 2000 individual ship emission plumes have been identified in the data and analyzed for the emission ratio of SO2 to NO2, yielding an average ratio of 0.3 for the years 2013/2014 and decreasing significantly, presumably due to lower fuel sulfur content, in 2015/2016. By sorting measurements according to the prevailing wind direction and selecting two angular reference sectors representative for wind from the open North Sea and coast excluding data with mixed air mass origin, relative contributions of ships and land-based sources to air pollution levels in the German Bight have been estimated to be around 40 % : 60 % for NO2 as well as SO2 in 2013/2014, dropping to 14 % : 86 % for SO2 in 2015/2016.

Investigating several ZrN plasmonic nanostructures and their effect on the absorption of organic solar cells

Broadband absorption enhancement is obtained in organic solar cells using zirconium nitride (ZrN) plasmonic nanostructures. Due to the thickness limitations imposed on organic solar cells, their absorption efficiency is limited. Plasmonic nanostructures have the ability to increase their optical efficiency by increasing the light path length inside the active material. Here, refractory plasmonics, a new type of plasmonic nanostructures, is used in organic solar cells instead of traditional metal plasmonics. ZrN, as an example of refractory plasmonics, has a high localized surface plasmon resonance quality factor in the visible range while being cheap, abundant, and C-MOS compatible. Here, several ZrN plasmonic nanostructures are studied including ZrN nanospheres, nanocubes, and nanoshells. Their Mie scattering and absorption efficiencies in a polymer environment are calculated. In addition, the effect of their incorporation on the absorbed power and short circuit current of organic solar cell is analyzed. ZrN nanodisks are also studied in different locations inside the solar cell with the best performance found for nanodisks placed at the interface between the active and the buffer layer. The highest absorption enhancement reported here is obtained when ZrN cubical nanoshells are added. A 34.7% increase in short circuit current is calculated for this structure.

Optimization of the Photoanode of CdS Quantum Dot-Sensitized Solar Cells Using Light-Scattering TiO2 Hollow Spheres

CdS quantum dot-sensitized solar cells (QDSCs) have been fabricated and their photoanode optimized by altering the thickness of the photoelectrode and CdS deposition conditions and applying a ZnS electron-blocking layer and TiO2 hollow spheres. Hydrothermally grown TiO2 nanocrystals (NCs) with dominant size of 20 nm were deposited as a sublayer in the photoanode with thickness in the range from 5 μm to 10 μm using a successive ionic layer adsorption and reaction (SILAR) method. The number of deposition cycles was altered over a wide range to obtain optimized sensitization. Photoanode thickness and number of CdS sensitization cycles around the optimum values were selected and used for ZnS deposition. ZnS overlayers were also deposited on the surface of the photoanodes using different numbers of cycles of the SILAR process. The best QDSC with the optimized photoelectrode demonstrated a 153% increase in efficiency compared with a similar cell with ZnS-free photoanode. Such bilayer photoelectrodes were also fabricated with different thicknesses of TiO2 sublayers and one overlayer of TiO2 hollow spheres (HSs) with external diameter of 500 nm fabricated by liquid-phase deposition with carbon spheres as template. The optimization was performed by changing the photoanode thickness using a wide range of CdS sensitizing cycles. The maximum energy conversion efficiency was increased by about 77% compared with a similar cell with HS-free photoelectrode. The reason was considered to be the longer path length of the incident light inside the photoanode and greater light absorption. A ZnS blocking layer was overcoated on the surface of the bilayer photoanode with optimized thickness. The number of CdS sensitization cycles was also changed around the optimized value to obtain the best QDSC performance. The number of ZnS deposition cycles was also altered in a wide range for optimization of the photovoltaic performance. It was shown that the maximum efficiency was increased by about 55% compared with a similar QDSC with ZnS-free bilayer photoanode. The final improvement was carried out by applying methanol-based Cd precursor solution in the SILAR deposition process. The best photoanodes from the previous stages were selected and used in this sensitizing process. Besides, nanocrystalline TiO2 sublayers with different thicknesses were applied for further optimization. The results revealed that maximum power conversion efficiency of 3.7% was achieved as a result of such improvement, for a QDSC with optimized double-layer photoanode including TiO2 HSs and NCs and ZnS blocking layer.

How to facet gem-quality chrysoberyl: Clues from the relationship between color and pleochroism, with spectroscopic analysis and colorimetric parameters

Pleochroism plays an important role in determining the face-up visual color appearance of faceted, optically anisotropic (non-cubic) gemstones. One area that has received little attention is the interplay between pleochroism and the so-called alexandrite effect wherein the perceived color of a mineral changes with different lighting conditions (i.e., daylight vs. incandescent light). In this article we have collected ultraviolet/visible/near-infrared (UV-Vis-NIR) spectra of a gem-quality, synthetic Cr-bearing chrysoberyl crystal along its three crystallographic axes. We use these spectra to calculate the color and to quantify the color change that would be observed in a wafer or faceted gemstone in any orientation and for any prescribed path length of light between 1 and 25 mm. We describe the method used to perform these calculations and give an overview of color science and color space as it pertains to mineralogy and gemology. The data collected here are used to predict the optimum orientation for a wafer or a faceted alexandrite gemstone to produce the maximum color change sensation between daylight and an incandescent light source. We find that a wafer oriented with the unpolarized light-path-length perpendicular to the a-axis exhibits the strongest color change but that the color change is weaker parallel to the a-axis. Pleochroism in a faceted stone will mix light traveling in different directions. This relaxes requirements to orient a stone along the “best” direction, but it is still found that stones cut with their table to culet direction oriented perpendicular to the a-axis show the best color-change while orientation parallel to the a-axis produces weaker color change. Nonetheless, there is a wide range of “acceptable” orientations and no single “best” direction for a faceted gemstone. The results of this study demonstrate the complex nature of color in minerals and shed light on the intricate interplay between several factors including pleochroism, lighting conditions, light path length through a transparent sample, and chromophore concentrations. The use of the techniques outlined here can lead to a better understanding of the color sciences in the mineral world in general.

Characterization of strongly scattering nanoporous materials as miniaturized multipass cell for tunable diode laser absorption spectroscopy

Through the confinement of gas in nanoporous materials, it is possible to significantly increase the path length for light–gas interaction. This enables the observation of much stronger absorption features for the confined gas molecules. In this work, we systematically characterized a variety of disordered strongly scattering ZrO $$_2$$ and Al $$_2$$ O $$_3$$ nanoporous ceramic materials to exploit the potential of gas in scattering media absorption spectroscopy. As a result, we identified a material with an unprecedented performance in terms of optical path length enhancement. In ZrO $$_2$$ with thicknesses above 6 mm, the path enhancement exceeds 1000. The results obtained with near-infrared absorption spectroscopy on oxygen were validated by time-of-flight measurements at 700 nm, thus demonstrating their robustness. Finally, we report quantitative oxygen concentration measurement using nanoporous materials as miniaturized random-scattering multipass cell with an extremely simple and low-cost setup.

Simultaneous enhancement of light absorption and improved charge collection in PTB7-Th: PC70BM organic solar cells

ABSTRACTEnhancing the light absorption and improving the charge collection are considered as two major prerequisite for achieving highly efficient bulk heterojunction organic solar cells (BHJ OSCs). In the present study, we have explored Ga doped ZnO as an electron transport layer for improving the charge collection in one of the promising donor: acceptor system comprised of Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th):phenyl-C71-butyric acid methyl ester (PC70BM). With the inverted geometry having a configuration of ITO/GZO (40nm)/PTB7-Th: PC70BM (100nm)/MoO3 (10nm)/Ag (100nm), maximum power conversion efficiency (PCE) of 7.24% has been achieved, while it is limited at 6.89% for devices with undoped ZnO.It was found that PCE can be further improved to 8.35 % after V-grooved textured PDMS films were attached to the backside of OSC substrates. We attribute this performance enhancement in OSCs is due to increased total optical path length of the incident light within the device.

Investigation of Simultaneous Effects of Aerosol Properties and Aerosol Peak Height on the Air Mass Factors for Space-Borne NO2 Retrievals

We investigate the simultaneous effects of aerosol peak height (APH), aerosol properties, measurement geometry, and other factors on the air mass factor for NO2 retrieval at sites with high NO2 concentration. A comparison of the effects of high and low surface reflectance reveals that NO2 air mass factor (AMF) values over a snowy surface (surface reflectance 0.8) are generally higher than those over a deciduous forest surface (surface reflectance 0.05). Under high aerosol optical depth (AOD) conditions, the aerosol shielding effect over a high-albedo surface is revealed to reduce the path-length of light at the surface, whereas high single scattering albedo (SSA) conditions (e.g., SSA = 0.95) lead to an increase in the aerosol albedo effect, which results in an increased AMF over areas with low surface reflectance. We also conducted an in-depth study of the APH effect on AMF. For an AOD of 0.1 and half width (HW) of 5 km, NO2 AMF decreases by 29% from 1.36 to 0.96 as APH changes from 0 to 2 km. In the case of high-AOD conditions (0.9) and HW of 5 km, the NO2 AMF decreases by 240% from 1.85 to 0.54 as APH changes from 0 to 2 km. The AMF variation due to error in the model input parameters (e.g., AOD, SSA, aerosol shape, and APH) is also examined. When APH is 0 km with an AOD of 0.4, SSA of 0.88, and surface reflectance of 0.05, a 30% error in AOD induces an AMF error of between 4.85% and −3.67%, an SSA error of 0.04 leads to NO2 VCD errors of between 4.46% and −4.77%, and a 30% error in AOD induces an AMF error of between −9.53% and 8.35% with an APH of 3 km. In addition to AOD and SSA, APH is an important factor in calculating AMF, due to the 2 km error in APH under high-SZA conditions, which leads to an NO2 VCD error of over 60%. Aerosol shape is also found to have a measureable effect on AMF under high-AOD and small relative azimuth angle (RAA) conditions. The diurnal effect of the NO2 profile is also examined and discussed.

Photodetector based on Vernier-Enhanced Fabry-Perot Interferometers with a Photo-Thermal Coating

We present a new type of fiber-coupled photodetector with a thermal-based optical sensor head, which enables it to operate even in the presence of strong electro-magnetic interference and in electrically sensitive environments. The optical sensor head consists of three cascaded Fabry-Perot interferometers. The end-face surface is coated with copper-oxide micro-particles embedded in hydrogel, which is a new photo-thermal coating that can be readily coated on many different surfaces. Under irradiation, photons are absorbed by the photo-thermal coating, and are converted into heat, changing the optical path length of the probing light and induces a resonant wavelength shift. For white-light irradiation, the photodetector exhibits a power sensitivity of 760 pm/mW, a power detection limit of 16.4 μW (i.e. specific detectivity of 2.2 × 105 cm.√Hz/W), and an optical damage threshold of ~100 mW or ~800 mW/cm2. The response and recovery times are 3.0 s (~90% of change within 100 ms) and 16.0 s respectively.

Effect of residence time on micropollutant removal in WWTP secondary effluents by continuous solar photo-Fenton process in raceway pond reactors

The removal of micropollutants (MPs) in wastewater treatment plants (WWTPs) secondary effluents by solar photo-Fenton is commonly carried out with low concentrations of iron and hydrogen peroxide due to the low pollutant concentration (ngL−1). This led to two main consequences being observed: short treatment times (tens of minutes) and excess of photons when using 5cm-diameter tubular reactors. To make better use of most of the photons reaching the reactor surface, the use of raceway pond reactors (RPRs) with longer light path length was implemented successfully. However, little attention was paid to the treatment time itself and the photo-Fenton process was applied in batch mode despite filling and emptying stages being much longer than reaction time. This paper deals with the performance of the solar photo-Fenton process in RPRs operated in continuous mode to remove MPs in WWTP secondary effluents. In this regard, first the continuous degradation of a model emerging contaminant, the pesticide Acetamiprid (ACTM), was studied in a synthetic secondary effluent at pH 2.8. Next, real secondary effluents were treated at two liquid depths, 5 and 15cm and three hydraulic residence times (HRTs), 80, 40 and 20min. Reactant concentrations were 5.5mgL−1 Fe2+ and 30mgL−1 H2O2 giving rise to a treated wastewater volume of 450Lm−2day−1 for a 5cm-deep RPR operated in continuous mode at 40min HRT for 6h a day in winter, with 84% MP removal and 66% hydrogen peroxide conversion. As far as the authors know, this is the first report on the solar photo-Fenton process operated in continuous mode displaying its advantages with regard to the batch operation.

Modulated III–V Triple-Junction Solar Cell Wireless Device for Efficient Water Splitting

We report an efficient wireless device for water splitting using III–V triple-junction solar cells. To maximize the generation efficiency of hydrogen, the surface catalytic electrode has to be well designed to balance with the capability of the solar cell. We find that another important parameter is the path length of light in water, which needs to be short enough to sufficiently activate the germanium bottom layer in the solar cell. The solar-to-hydrogen conversion efficiency of the wireless device under 1 sun illumination without an external bias reaches 11.2% at almost neutral pH, and stoichiometric evolution of hydrogen and oxygen is confirmed.

Application of ZnO micro rods on the composite photo-electrode of dye sensitized solar cells

In this study, we prepared low-density ZnO micron rods (MRs) on ITO/PEN substrate by hydrothermal method, and used the scraper to fill the ZnO nanoparticles into the micron rods to prepare ZnO composite structure as the photo-electrode of dye sensitized solar cells (DSSCs). The nanostructures and photo-electrodes were investigated by field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), incident photon conversion efficiency (IPCE) and I–V characteristics analyses. In the results of FE-SEM, they show that the average length of the ZnO MRs and the thickness of ZnO film are 14 and 33.1 μm, respectively. EIS analyses show that there is a minimal RK and the longest electron lifetime of DSSCs with the ZnO composite structure, which means less recombination of the electrons in the ZnO composite structure. The results of IPCE indicate that the photo-electrode of ZnO composite structure exhibits the best quantum efficiency about 81.7%. It may be due to ZnO MRs play as a light scattering layer resulting in the increase of path length for the incident light, thereby increasing the collision probability between the incident light and the ZnO nanoparticles. In addition, we also compared the I–V characteristics of three different photo-electrodes with ZnO NPs, ZnO NPs pressed 418.8 kg/cm2 and ZnO composite structure. The best structure is ZnO composite structure, and it has the best current density (JSC = 10.59 mA/cm2) and overall conversion efficiency (η = 3.46%) of dye-sensitized solar cells.

Direct measuring of single-cycle mid-IR light bullets path length in LiF by the laser coloration method

A colour-centre structure formed in a LiF crystal under filamentation of a femtosecond mid-IR laser pulse with a power slightly exceeding the critical power for self-focusing has been experimentally and theoretically investigated. A single-cycle light bullet was recorded for the first time by observation of strictly periodic oscillations for the density of the color centers induced in an isotropic LiF crystal under filamentation of a laser beam with a wavelength tuned in the range from 2600 to 3900 nm, which is due to the periodic change in the light field amplitude in the light bullet formed under filamentation under propagation in dispersive medium. The light bullet path length was not more than one millimeter.

An Optical Path Length Modulator for Laser Diode Self-Mixing Interference

Transparent liquid flattening or stretching realizes optical path length modulation. A flat thin seal transparent cavity, one flank is an electromagnetic driving membrane and is filled over with transparent liquid. Vibration of the membrane makes the liquid compressing or stretching, changes the liquid layer thickness, i.e. the optical path length of light through the liquid layer. The liquid layer compressed is equivalent to increase membrane tension. The membrane has higher resonant frequency. The cavity diameter 10 mm modulation frequency is about 18 kHz.

Hexagonal mesoporous silica islands to enhance photovoltaic performance of planar junction perovskite solar cells

Wormhole-like hexagonal mesoporous silica (HMS) can modify the perovskite morphology and increase the light path length in a planar junction perovskite solar cell to improve the average PCE to 17.6% over 30 devices.

Canopy Net Photosynthesis Rate of a Mongolian Oak (<i>Quercus mongolica</i>) Forest Estimated by Field Experimental Data

The canopy net photosynthesis rate of Mongolian oak (Quercus mongolica) tree species that are dominant in East Asia and Korea is estimated with empirical models derived from field experimental data obtained from the Nam-San site in Seoul, Korea for the growing period from early May to late October in 2010. The empirical models include the attenuation function of photosynthetic photon flux density (PPFD) (r2 = 0.98-0.99, p r2 = 0.99, p level within canopy significantly varies diurnally and seasonally due to the seasonal variation of the total plant area index (TPAI = leaf area index + wood silhouette area index) and the light shielding effect of light path-length through the canopy in association with the variation of solar elevation angle. Consequently, a remarkable seasonal variation of the total canopy net photosynthesis rate of Q. mongolica forest stand is found for its growing period. The PPFD exceeding 1000 μmol m-2·s-1 is found to cause the decrease of net photosynthesis rate due to the thermal stress in the early (May) and late (September) growing period. During the whole growing season, the estimated total canopy net photosynthesis rate is found to be about 3.3 kg CO2 m-2.

Measuring the Spectrum of Extinction Coefficient and Reflectance for Cadmium Compounds from 400 to 900 nm

The key to extract the contents of cadmium in water by using remote sensing technique is to measure the spectrum of extinction coefficient per g·L(-1) and reflectance for its compounds. So in this paper, firstly, we choose two kinds of cadmium compounds, cadmium sulfide (CdS) and cadmium oxide (CdO), which are most commonly exsit in natural water, to measure the spectrums of extinction coefficient and reflectance for them. We use the equipment, designed on our own, which can adjust the path length of light passing and make our measuring results more accurate at visible and near-infrared wavelength range than others. Then we use Analytical Spectral Devices (ASD) spectrometer to measure the radiance of the light spot, which is from the direct light passed through cadmium compounds solutions of different concentrations reflected by the standard board. Using the ratio method to eliminate environmental errors and the effects of the thimbleful of suspended solids in water, we obtain the extinction coefficient per g·L(-1) of these two kinds of cadmium compounds from 400 to 900 nm. Secondly, we use ASD spectrometer to measure the reflectance spectrum of them in the sunny day at outdoor. The reflectance we obtain in this paper can help us to calculate the absorption and scattering coefficient per g·L(-1) in the future. The measuring results show that the extinction coefficient spectrum of CdS has two troughs at 550 and 830 nm and one peak at 675 nm. And the extinction coefficient spectrum of CdO decrease from purple to near-infrared. Both of their coefficient spectrums in blue are larger than green and red. And the value of the extinction coefficient per g·L(-1) of CdS is larger than CdO in the whole measuring wavelength range. The reflectance of CdS in yellow and red is larger than purple and blue, which increases rapidly from 500 to 650 nm and then leveling off. While the reflectance of CdO increase linearly from 525 to 900 nm. Both have obvious spectral characteristic. According to our results, the largest extinction coefficient appear at blue color, while the largest reflectance appear at yellow and red, which means that those bands are the most sensitive wavelength to detect the change of cadmium concentration in water. This study carries out with optical parameters measurements for optical activity of cadmium compounds specifically for water quality remote sensing for the first time. We conclude that the extinction coefficient and reflectance spectrums we obtained are reasonable, and the results can be used as the base parameter in the remote sensing inversion model for cadmium contents in water, which provides a breakthrough on using remote sensing technique to extract the heavy metal contents in water. Obtained these two optical parameters in this paper can provide powerful reference for band selection of the remote sensing image, which is used to extract cadmium contents in water, as well as provide the necessary important parameters of the remote sensing inversion model of cadmium contents in water.

Compressed-tube pressure cell for optical studies at ocean pressures: Application to glucose mutarotation kinetics.

A self-contained compressed-tube pressure cell is tested to 25 MPa. The cell is very simple to construct and offers stable pressure control with optical access to fluid samples. The physical path length of light through the cell is large enough to measure optical activity. The entire system is relatively small and portable, and it is vibration-free, since a compressor is not used. Operation of the cell is demonstrated by measuring the mutarotation rate of aqueous glucose solutions at 25 °C. A logarithmic plot of the rate constant vs. pressure yields an activation volume for mutarotation of -22 cm3/mol, approximately twice the value measured previously at higher pressures.

Enhancement of the atomic absorbance of Cr, Zn, Cd, and Pb in metal furnace atomic absorption spectrometry using absorption tubes

Trace amounts of Cr, Zn, Cd, and Pb were determined by metal furnace atomic absorption spectrometry using absorption tubes. Various absorption tubes were designed as roof- and tube-types, and fixed above the metal furnace in order to extend the light path length. Aqueous standards and samples were injected in the metal furnace and atomized in a metal atomizer with an absorption tube (6 cm length, 15.5 mm diameter). The used of an absorption tube resulted in an enhancement of the atomic absorbance. The ratios of absorbance values with and without the roof- and tube-type absorption tubes were 1.33 and 1.11 for Cr; 1.42 and 1.99 for Zn; 1.66 and 1.98 for Cd; and 1.31 and 1.16 for Pb, respectively. The use of an absorption tube was effective for Zn and Cd analysis, as the absorbance values for these low boiling point metals doubled. The proposed method was successfully applied in the determination of Zn in tap water.

Efficient light trapping and interface engineering for performance enhancement in PTB7-Th: PC70BM organic solar cells

Inefficient light absorption and poor charge separation are considered as two major bottlenecks for achieving highly efficient bulk heterojunction organic solar cells (BHJ OSCs). In the present study, we have introduced an additional phenyl-C71-butyric acid methyl ester (PC70BM) layer to modify the interface between ZnO based electron transport layer (ETL) and photoactive layer comprised of Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b; 4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thio-phene-)-2-carb-oxylate-2-6-diyl)] (PTB7-Th):PC70BM. This interface engineering has quenched the electron–hole recombination at the interface and has improved power conversion efficiency (PCE) from 6.65 to 7.74%. Devices were fabricated in an inverted geometry having a structure ITO/ZnO (40 nm)/PC70BM (5 nm)/PTB7-Th:PC70BM (70 nm)/MoO3 (10 nm)/Ag (100 nm). Additionally, V-grooved textured PDMS films were attached to the backside of OSC substrates which has further improved PCE to 9.12%. Our study suggests that the performance enhancement as observed in OSCs with V-grooved textured PDMS films could be due to increased total optical path length of the incident light within the device.

3D-Array of Au-TiO2 Yolk-Shell as Plasmonic Photocatalyst Boosting Multi-Scattering with Enhanced Hydrogen Evolution.

Nowadays, how to convert solar energy efficiently to other energies, such as chemical energy, is an important subject. In the present work, gold nanosphere (AuNS) monoencapsulated in TiO2 hollow nanosphere (Au-TiO2) and three-dimensional assembled array of Au-TiO2 (3D-array) were fabricated to carefully explore the multiscattering effect on the photocatalytic activity of H2 generation under simulated solar light and visible light irradiation, respectively. Au-TiO2 with the inner cavity diameter of 176 nm was uniformly synthesized via SiO2 protection method and then was used as building blocks for construction of 3D-array. The 3D-array exhibited a much higher photocatalytic activity of H2 generation (3.5 folds under visible light irradiation, 1.4 folds under solar light irradiation) than Au-TiO2. Single-particle plasmonic photoluminescence measurement and computational simulation of finite difference time domain (FDTD) were performed to elucidate the detailed mechanisms of photocatalysis. It was suggested that the hot electrons generated by AuNS under visible light irradiation play a significant role during the photocatalysis process. The higher activity of 3D-array is due to the elongation of light path length because of the multiscattering in-between Au-TiO2 and the reflection inside of the TiO2 shell. Therefore, the AuNS has more opportunity to absorb light and more hot electrons are expected to be generated through the electron transfer from AuNS to TiO2 shell, leading to an increment in the H2 generation. This result gives us a new perspective of constructing structures for efficient light utilization.