Wide Range Of Visible Light Research Articles

Cu3 MS4 (M=V, Nb, Ta) and its Solid Solutions with Sulvanite Structure for Photocatalytic and Photoelectrochemical H2 Evolution under Visible-Light Irradiation.

Solid solutions with of Cu3 VS4 with either Cu3 NbS4 or Cu3 TaS4 (Cu3 Nb1-x Vx S4 or Cu3 Ta1-x Vx S4 ) were prepared by a solid-state reaction and adopted a sulvanite structure. Their band gaps were 1.6-1.7 eV corresponding to the absorption of a wide range of visible light. Ru cocatalyst-loaded Cu3 MS4 (M=V, Nb, Ta), Cu3 Nb1-x Vx S4 , and Cu3 Ta1-x Vx S4 showed photocatalytic activities for sacrificial H2 evolution under visible-light irradiation. Most solid solutions showed better activities than the single-component Cu3 MS4 (M=V, Nb, Ta). Cu3 MS4 (M=V, Nb), Cu3 Nb1-x Vx S4 , and Cu3 Ta1-x Vx S4 also functioned as photoelectrodes and gave cathodic photocurrents under visible-light irradiation, indicating a p-type semiconductor character. Cu3 Nb0.9 V0.1 S4 showed the best photocatalytic and photoelectrochemical performances. When Ru-loaded Cu3 Nb0.9 V0.1 S4 was used as a photocathode with a CoOx -loaded BiVO4 photoanode, photoelectrochemical water splitting proceeded under simulated sunlight irradiation without an external bias.

Efficient Solar‐Driven Water Oxidation over Perovskite‐Type BaNbO2N Photoanodes Absorbing Visible Light up to 740 nm

AbstractPhotoelectrochemical water splitting using semiconductors absorbing a wide range of visible light is a potentially attractive means of harvesting large portions of the solar spectrum. However, this is also very challenging because narrowing the semiconductor band gap lowers the driving force for photoreactions. Herein, a highly active perovskite BaNbO2N exhibiting photoexcitation up to 740 nm for water oxidation is reported. The synthesis route, consisting of moderate nitridation and subsequent annealing in inert Ar flow, enhances the crystallinity of the BaNbO2N surface without inducing the reduction of the Nb species. As a result, a particulate BaNbO2N photoanode exhibits a photocurrent of 5.2 mA cm−2 at 1.23 VRHE under simulated solar irradiation, which is the highest yet reported for an oxynitride responsive at wavelengths above 600 nm. Suppressing the reduction of B‐site cations during the synthesis of perovskite AB(O,N)3, which otherwise results in surface defects or impurities, is critical for achieving high water oxidation activity.

PtIx/[(CH3)2NH2]3[BiI6] as a well-dispersed photocatalyst for hydrogen production in hydroiodic acid

Constructing a photocatalytic system for hydrogen generation is a promising means for producing clean and renewable energy. However, developing photocatalysts with high efficiency in a wide range of visible light is still a formidable challenge. Here, we report on a highly active system for photocatalytic hydrogen production from hydroiodic acid splitting that contains a soluble organic-inorganic hybrid PtIx/[(CH3)2NH2]3[BiI6] as a newcomer photocatalyst for harvesting a wide range of visible light (up to 630 nm). Under irradiation at 465 nm, the photocatalytic system achieves apparent quantum yield of ~82.8% for photocatalytic hydrogen production along with a stable activity for at least 100 h. We propose that the superior photocatalytic performance is attributed to collisions between [BiI6]3− and Pt ions (Pt2+ or Pt4+), giving rise to efficient charge separation, which could be an effective approach towards designing and fabricating organic-inorganic semiconductors with improved performance in photocatalysis.

Study on the Photoresponse Characteristics of Organic Light-Emitting Field-Effect Transistors

Organic photodetectors have attracted great attention because of their promising applications in the fields of imaging, optical communication, and biosensing. Although the optical and electrical performances of the organic light-emitting field effect transistors (OLEFETs) have improved substantially in the past decade, the photodetection property of the OLEFETs has rarely been studied. Here, we investigated the photoresponse characteristics of the heterostructured OLEFETs, which unexpectedly shows performance comparable to some organic phototransistor-only devices, without sacrificing the light emission performance of the device. The device shows photoresponse ability in a wide visible light range and a maximum photon-to-electron efficiency of 45 300% with millisecond-scale switching on and off time when under the illumination of 405 nm. It is found that the photoresponse characteristics of the devices are mainly determined by the hole injection layer, as light absorption happens mainly in this layer. Our...

Simple Hydrogen Plasma Doping Process of Amorphous Indium Gallium Zinc Oxide-Based Phototransistors for Visible Light Detection

A homojunction-structured amorphous indium gallium zinc oxide (a-IGZO) phototransistor that can detect visible light is reported. The key element of this technology is an absorption layer composed of hydrogen-doped a-IGZO. This absorption layer is fabricated by simple hydrogen plasma doping, and subgap states are induced by increasing the amount of hydrogen impurities. These subgap states, which lead to a higher number of photoexcited carriers and aggravate the instability under negative bias illumination stress, enabled the detection of a wide range of visible light (400-700 nm). The optimal condition of the hydrogen-doped absorption layer (HAL) is fabricated at a hydrogen partial pressure ratio of 2%. As a result, the optimized a-IGZO phototransistor with the HAL exhibits a high photoresponsivity of 1932.6 A/W, a photosensitivity of 3.85 × 106, and a detectivity of 6.93 × 1011 Jones under 635 nm light illumination.

Improved antireflection based on biomimetic nanostructures at material interface

Reducing light reflections on the surface of materials has important applications in many fields, such as solar cells, photodetectors, and optical sensors, etc. An effective method of decreasing reflection is using the anti-reflective coating with a gradient refractive index. In this study, we designed a nanostructure composed of optimized cone arrays on the flat thin film surface. The tapered nanostructure forms an anti-reflection layer. The effective refractive index of the anti-reflection layer changes smoothly with the depth so that the surface can efficiently reduce the reflection in a wide visible light range. Moreover, the reflection can also be modulated by adjusting the height and the period of the nanocones. Furthermore, there is an optimal wavelength at which the highest anti-reflection efficiency is achieved. The results here provide a theoretical guidance for the practical design of broadband anti-reflection nanostructures at the device surface.

Synthesis of Os(ii)-Re(i)-Ru(ii) hetero-trinuclear complexes and their photophysical properties and photocatalytic abilities.

Photofunctional trinuclear complexes containing three different central metals, i.e. Os(ii), Re(i) and Ru(ii), were synthesised for the first time using stepwise Mizoroki-Heck reactions. The vinylene groups in the bridging ligands of the Os(ii)-Re(i)-Ru(ii) trinuclear complexes were selectively reduced by photochemical hydrogenation in moderate yield, affording novel supramolecular photocatalysts which can absorb a wide range of visible light up to 730 nm and induce CO2 reduction with high selectivity and durability. The turnover numbers of CO formation were over 4300. Details of the photophysical properties of these new trinuclear complexes, especially their intramolecular excitation-energy transfer phenomena, are also reported.

Electronic and Optical Properties of Pristine and Vertical and Lateral Heterostructures of Janus MoSSe and WSSe.

On the basis of electron-electron self-energy corrections, quasiparticle band structures of Janus MoSSe and WSSe are identified, and the excitonic effects are demonstrated to play a dominate role in the optical response. Combining together MoSSe and WSSe monolayers to form vertical heterostructures (VHTs) and lateral heterostructures (LHTs) rarely leads to a simple arithmetic sum of their properties, giving rise to novel and unexpected behaviors. In particular, Rashba polarization can be enhanced in VHTs due to improved out-of-plane electric polarity. In the case of LHTs, photoresponse and absorption coefficients show optical activity in a wide visible light range. It is of interest that both VHTs and LHTs reveal type-II band alignment, enabling the separation of excitons. Besides, grain boundaries (GBs) of large angle (60°) in Janus MoSSe due to chalcogen effects behave as one-dimensional (1D) metallic quantum wires, suggesting the possible formation of 1D electron or hole gas in such electronic heterostructures.

Novel Visible-Light-Driven Photocatalyst Co3O4/FeWO4 for Efficient Decomposition of Organic Pollutants

A highly efficient and visible light (λ ≥ 420 nm) responsive composite photocatalyst, Co3O4/FeWO4 was prepared by simple impregnation method. The heterojunction semiconductors Co3O4/FeWO4 demonstrated notably high photocatalytic activity over a wide range of composition than the individual component Co3O4 or FeWO4 for the complete degradation of 1,4-dichlorobenzene (DCB) in aqueous phase under visible light irradiation. The photocatalytic activity of composite was optimized at 1/99 Co3O4/FeWO4 composition. After 2 h of visible light irradiation 51% decomposition of 1,4-dichlorobenzene (DCB) was observed utilizing 1/99 Co3O4/FeWO4 photocatalyst while the end members demonstrated a negligible degradation under the same experimental condition. The valence band (VB) and conduction band (CB) of Co3O4 is located above the VB and CB of FeWO4, respectively. Both the semiconductors Co3O4 and FeWO4 exhibit strong absorption over the wide range of visible light. The obviously enhanced photocatalytic performance of Co3O4/FeWO4 composite has been discussed on the hole (h+) as well as electron (e−) transfer mechanism between the VB and CB of individual semiconductors.

Investigation on Nitridation Process of SrNbO2N Particles from SrNbO3 for Photoelectrochemical Water Splitting

Hydrogen produced from water using renewable energy has been investigated as a next-generation energy carrier. Photoelectrochemical (PEC) water splitting is a potential candidate for clean hydrogen production with reasonable cost. Considering utilization of sunlight as an energy source, photocatalysts need to absorb a wide range of visible light. SrNbO2N is an attractive material with an absorption edge of 690 nm and works as a photoanode in a PEC system.1 Photoelectrochemical properties of SrNbO2N particles are greatly affected by their oxide precursors and nitridation conditions. Therefore it is thought that understanding nitridation mechanism is a critical issue to activate PEC properties of oxynitrides. In this study, a novel oxide precursor SrNbO3 and subsequently nitrided SrNbO2N was investigated. SrNbO3 oxide precursor was synthesized by a solid state reaction under an Ar flow.2 A mixture of Nb and Sr5Nb4O15 which was synthesized by calcining a stoichiometric mixture of SrCO3 and Nb2O5 in advance was heated under an Ar flow at 1773 K for 20 h. Obtained oxide precursors were nitrided under an ammonia flow at 1173 K for different time. Photoelectrodes of synthesized particles were fabricated by particle transfer method.3Nitridation process of oxide precursors were investigated based on X-ray diffraction, diffuse reflectance spectra and elemental analysis as which were combined oxygen-nitrogen analysis with inductively coupled plasma atomic emission spectroscopy (ICP-AES) as well as PEC properties. SrNbO3 and SrNbO2N nitrided for more than 20 h both had a perovskite-type structure. At the initial stage of nitridation, however, SrNbO3 was separated to Sr5Nb4O15 and SrNbO3-x N y then gradually nitrided to SrNbO2N as shown in Fig. 1. This phase separation appeared due to introduction of N atoms to oxidize Nb4+ to Nb5+. According to progression of nitridation, photocurrent densities improved. This study shows the effect of oxide precursor on the PEC performance of resulting oxynitrides. Nitridation mechanism affected by the crystal structure of oxide precursors is also discussed. 1) M. Kodera, H. Urabe, M. Katayama, T. Hisatomi, T. Minegishi and K. Domen, J. Mater. Chem. A, 2016, 4, 7658–7664. 2) X. Xu, C. Randorn, P. Efstathiou and J. T. Irvine, Nat. Mater., 2012, 11, 595–598. 3) T. Minegishi, N. Nishimura, J. Kubota and K. Domen, Chem. Sci., 2013, 4, 1120–1124. Figure 1

Surface-Modified Metal Sulfides As Stable H2 Evolving Photocatalyst in Z-Scheme Water Splitting System with [Fe(CN)6]3–/4– Redox Mediator Under Visible Light Irradiation

Photocatalytic water splitting using semiconductor materials has attracted considerable attention due to the potential for the clean production of H2 from water by utilizing solar energy. Since nearly half of the solar energy incident on the Earth’s surface lies in the visible region, an efficient harvest of wide range of visible light is essential for realizing practically high efficiency in the photocatalytic H2 production under natural sunlight. Most of metal sulfide semiconductors, such as CdS, possess appropriate band levels for water reduction and oxidation as well as a narrow band gap allowing visible light absorption because the valence bands of them are mainly formed by S 3p orbital. However, the most of sulfides have no capability of O2 evolution from water due to the occurrence of self-oxidative deactivation by photogenerated holes. Even for the sacrificial H2 evolution, they require particular electron donor such as S2– and SO3 2– to generate H2 stably. In the present study, we introduce a new and versatile way that can stabilize metal sulfides, not only CdS but also others such as ZnIn2S4 and CdIn2S4, as H2-evolving photocatalyst in Z-scheme water splitting with [Fe(CN)6]3–/4– redox. Pt/CdS was found to generate considerable amount of H2 from water in the presence of [Fe(CN)6]4– under visible light, while the H2 evolution was soon terminated at ca. 28 µmol in the unbuffered aqueous solution (Fig. 1). However, the production of nearly the twice amount (ca. 53.6 µmol) of oxidant, i.e., [Fe(CN)6]3–, was confirmed in the solution after the reaction. This result indicated that photocatalytic H2 evolution over Pt/CdS proceeded under visible light irradiation, accompanied by the oxidation of [Fe(CN)6]4– to [Fe(CN)6]3–. The cease of H2 evolution was due to increased pH value (6.7 → 10.7). Then, it was found that the use of borate buffer (BB) was effective to suppress such decrease in H2evolution rate. Photocatalytic H2 evolutions over other metal sulfides (ZnIn2S4 and CdIn2S4) were also examined in the presence of [Fe(CN)6]4–. Pt/ZnIn2S4 showed appreciable H2 evolution rate (4.8 µmol/h). On the other hand, Pt/CdIn2S4 showed quite low activity (0.8 µmol/h). ATR-FTIR analysis revealed that hexacyano complexes, such as M x [CdFe(CN)6]1) and M x [ZnFe(CN)6]2) were formed on Pt/CdS and Pt/ZnIn2S4, respectively, after each reaction, both of which showed appreciable H2 evolution. These hexacyano complexes would be generated from the reaction of [Fe(CN)6]3–/4– and Cd2+ or Zn2+ ion derived from photocorrosion during photocatalytic reaction. Rubin et al. have reported that such hexacyano complex formed on CdS electrode efficiently scavenged photogenerated holes, leading to increased rate of oxidation of [Fe(CN)6]4– and also suppression of photocorrosion of CdS. To improve the activity for H2 evolution, the hexacyano complex K2[CdFe(CN)6] prepared in advance, was loaded onto ZnIn2S4 and CdIn2S4 particles. The loading indeed improved the H2 evolution rate in both cases (ZnIn2S4: 4.8 →15 µmol/h, CdIn2S4: 0.8 → 6 µmol/h). Finally, we demonstrated that combination of metal sulfides as H2-evolving photocatalyst and O2 evolution system (TaON photoanode3)) could split water stably into H2 and O2 under visible light irradiation (Fig. 2).

Anatase (101)-like Structural Model Revealed for Metastable Rutile TiO2(011) Surface.

Titanium dioxide has been widely used as an efficient transition metal oxide photocatalyst. However, its photocatalytic activity is limited to the ultraviolet spectrum range due to the large bandgap beyond 3 eV. Efforts to reduce the bandgap to achieve a broader spectrum range of light absorption have been successfully attempted via the experimental synthesis of dopant-free metastable surface structures of rutile-type TiO2 (011) 2 × 1. This new surface phase possesses a reduced bandgap of ∼2.1 eV, showing great potential for an excellent photocatalyst covering a wide range of visible light. There is a need to establish the atomistic structure of this metastable surface to understand the physical cause for the bandgap reduction and to improve the future design of photocatalysts. Here, we report computational investigations in an effort to unravel this surface structure via swarm structure-searching simulations. The established structure adopts the anatase (101)-like structure model, where the topmost 2-fold O atoms form a quasi-hexagonal surface pattern and bond with the unsaturated 5-fold and 4-fold Ti atoms in the next layer. The predicted anatase (101)-like surface model can naturally explain the experimental observation of the STM images, the electronic bandgap, and the oxidation state of Ti4+. Dangling bonds on the anatase (101)-like surface are abundant making it a superior photocatalyst. First-principles molecular dynamics simulations have supported the high photocatalytic activity by showing that water and formic acid molecules dissociate spontaneously on the anatase (101)-like surface.

Electro- and opto-mutable properties of MgO nanoclusters adsorbed on mono- and double-layer graphene.

Inspired by recent experiments, the trapping of molecules in 2D materials has gained increasing attention due to the unique ability of the molecules to modulate the electronic and optical properties of 2D materials, which calls for fundamental understanding and predictive design strategies. Herein, we focus on mono- and double-layer graphene encapsulating various MgO clusters and explore their diverse electronic and optical properties using a number of high-level first-principles calculations. By correlating the stability of adsorption, geometry, charge transfer, band structures, optical absorption spectrum, and the van der Waals pressure, our results decode various synergies in electro- and opto-mutable properties of MgO/graphene systems. We found that 2D-MgO flakes on graphene layers exhibit surface polarization effects - in contrast to their isolated neutral flakes - and show a significant charge transfer from graphene to n-doped flakes, breaking the symmetry of graphene layers. We obtained a van der Waals pressure of ∼0.7 (0.9) GPa on bilayer graphene encapsulating MgO nanoclusters, which matches extremely well with experiment. While there is one quantum emission in the visible light region for a single MgO flake, a wide range of visible light is accessible for MgO on mono- and double-layer graphene. Overall, these findings provide new physical insights and design strategies to modulate 2D materials with several applications in optoelectronics while significantly broadening the spectrum of strategies for fabricating new hybrid 2D heterostructures by encapsulating external molecules.

Artificial Photocatalytic System Using Polydiacetylene-(−NH-phen)Ru(bpy)2 for Cofactor Regeneration and CO2 Reduction

For the practical use of a photobioreactor for artificial photosynthesis, efficient visible light-absorbing materials have to link reduction and oxidation catalysts for an efficient energy flow. As a step toward this goal of an NADH regeneration system and enzymatic production of solar fuels from CO2, we report the synthesis of a new polydiacetylene compound that is covalently connected with [Ru(phen-NH2) (bpy)2]2+ (bpy =2,2′-bipyridine, phen =1,10-phenonthroline-5-amine). The [(bpy)2Ru(phen-NH−)]-polydiacetylene absorbed a wide range of visible light because of the presence of two chromophores, the Ru complex and polydiacetylene. The polyacetylene backbone was converted from blue to red by conformational changes under the catalytic reaction conditions in a buffer solution. The electron transfer from the photoexcited [Ru(phen)(bpy)2]2+ to the polydiacetylene backbone was observed. In a visible light-driven photocatalytic NAD+ reduction by (cyclopentadienyl)Rh(bpy)(H2O)2+ with [(bpy)2Ru(phen-NH−)]-polydiac...

Fabrication of ZnO-ZnS@polyaniline nanohybrid for enhanced photocatalytic degradation of 2-chlorophenol and microbial contaminants in wastewater

In this work, a visible light active semiconductor photocatalyst ZnO-ZnS@polyaniline (ZnO-ZnS@Pani) nanocomposite was synthesized and its application was investigated for the photocatalytic degradation of organic and microbial contaminants in aqueous solution. The morphology and structural characteristics of the prepared materials were analysed using X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, Raman analysis and X-ray photoelectron spectroscopy. The photocatalytic activity of ZnO-ZnS@Pani was investigated for the degradation of 2-chlorophenol (2-CP) in synthetic wastewater under visible light irradiation as a function of contact time, pH and initial pollutant concentration. The highest 89% degradation of 2-CP was achieved at the pollutant concentration of 50 mg/L and 0.5 g/L catalyst dose. The efficient degradation was achieved due to the polyaniline in ZnO-ZnS@Pani nanocomposite which absorbs a wide range of visible light and inceases the eletron/hole separation. Moreover, the catalyst showed high stability and retained its photocatalytic activity up to the maximum level even after multiple reuses. Furthermore, ZnO-ZnS@Pani showed excellent antimicrobial action in sunlight against water born fecal E. coli, where 13.4% more effectiveness was observed as compared to ZnO-ZnS. These results revealed that ZnO-ZnS@Pani is an efficent visible light catalyst and can be used for the decontamination of wastewater.

C-Dot Generated Bioactive Organosilica Nanospheres in Theranostics: Multicolor Luminescent and Photothermal Properties Combined with Drug Delivery Capacity.

Biocompatible nanomaterials that allow for labeling cells and tissues with the capacity to load and deliver drug molecules hold great promise for the therapeutic-diagnostic purposes in tissue repair and disease cure. Here a novel nanoplatform, called C-dot bioactive organosilica nanosphere (C-BON), is introduced to have excellent theranostic potential, such as controlled drug delivery, visible-light imaging, and NIR photothermal activity. C-dots with a few nanometers were in situ generated in the Ca-containing organosilica mesoporous nanospheres through the sol-gel and thermal-treatment processes. The C-BON exhibited multicolor luminescence over a wide visible-light range with strong emissions and high photostability over time and against acidity and the possible in vivo optical imaging capacity when injected in rat subcutaneous tissues. Moreover, the C-BON showed a photothermal heating effect upon the irradiation of near-infrared. The C-BON, thanks to the high mesoporosity and existence of Ca(2+) ions, demonstrated excellent loading capacity of anticancer drug doxorubicin (as high as 90% of carrier weight) and long-term (over a couple of weeks) and pH/NIR-dependent release ability. The C-BON preserved the compositional merit of Ca-Si glass, having excellent bioactivity and cell compatibility in vitro. Taken all, the multifunctional properties of C-BON-multicolor luminescence, photothermal activity, and high drug loading and controlled release-together with its excellent bioactivity and cell compatibility potentiate the future applications in theranostics (chemotherapy and photothermal therapy with optical imaging).

Grinding combined melt-diffusion synthesis of sulfur/P25 heterostructure for enhanced photocatalytic activity under visible light

A facile grinding combined melt-diffusion method has been developed to prepare sulfur/P25 heterostructure only using commercial sulfur and P25 as raw materials. This combination of sulfur with P25 not only extended the light absorption spectrum but also enhanced the separation efficiency of photoinduced charge carriers. In the sulfur/P25 heterostructure, sulfur acts as a photocenter for absorbing visible light to generate more charge carriers. The transfer of charge carriers between the anatase, rutile phase of TiO2, and sulfur components increases the charge separation efficiency. As a result, sulfur/P25 heterostructure exhibited much higher photocatalytic activity for degradation of methyl orange under visible light irradiation than commercial P25. Our results might open up a promising way to develop a novel and highly efficient TiO2-based heterostructure photocatalyst under a wide range of visible light.

Enhancing the photocatalytic H2evolution activity of red phosphorous by using noble-metal-free Ni(OH)2under photoexcitation up to 700 nm

Ni(OH)2 nanoparticles are demonstrated to be cost-efficient alternatives to Pt co-catalysts for enhancing the visible-light photocatalytic H2 evolution activity of red phosphorous (P) when deposited onto its surface. Ni(OH)2-modified red P exhibits 1.12 times higher photocatalytic activity for H2 evolution than that of Pt-deposited red P under a wide range of visible light.

Recent progress on photocatalysts with wide visible light range absorption for heterogeneous water splitting

Recent progress on wide visible light range photocatalysts for heterogeneous water splitting was summarized, and the next challenge of developing an efficient 600 nm class photocatalytic water splitting system was highlighted.

Photocatalytic Degradation of Phenol with Bacteriorhodopsin Sensitized TiO<sub>2</sub> Nanoparticles

Bacteriorhodopsin (BR) is a light driven proton pump firstly found in the membrane of halophilic archaea. BR absorbs wide range of visible light with high quantum efficiency. To elucidate the sensitizing effect of BR, we tested the photocatalytic degradation of phenol with BR-sensitized TiO2 nanoparticles and compared with that of Alizarin red (AR). When the concentration of BR was 13.1 mg/L (4.9×10-7 mol/L), 23.8% of phenol was degradated after 2 hours of light irradiation. The degradation percentage was 3.5 times higher than that with TiO2 nanoparticles alone and similar to that sensitized by AR (20.1%). The possibilities and approaches to increase the sensitizing performance of BR were discussed.