Increased Light Harvesting Research Articles

Enhanced photovoltaic efficiency in TiO2-based CdS quantum dot-sensitized solar cells by the introduction of ZnO:Al3+ nanoparticles

A technique to fabricate quantum dots-sensitized solar cells (QDSSCs) based on Titanium Oxide (TiO2) and Zinc Oxide (ZnO) nanoparticles (NPs) is reported. ZnO nanocubes of around 65 nm were synthesized by the sol–gel precipitation method. ZnO was doped with Al3+ to enhance the photovoltaic efficiency by promoting electron mobility to form an efficient photoelectrode added to TiO2. Current density–voltage (J-V) characterizations indicate that the addition of Al3+ doping in ZnO crystalline structure in the photoelectrode can significantly improve current densities and consequently the photoconversion efficiency (η) of the QDSSCs, achieving maximum η of 3.4 % with five ZnO nanocubes layers with a 0.0005 M Al3+ doping concentration. While with the undoped sample and bare TiO2, the obtained ήs were 2.85 and 1.93 %, respectively. The improved QDSSC photovoltaic performance was attributed to the increased light harvesting due to a large surface area by introducing Al-doped ZnO nanocubes into the available places of the TiO2 lattice. On the other hand, the increased electrical conductivity due to the Al3+ ion doped into the ZnO lattice at the divalent Zn2+ site allows electrons to move readily into the Al-doped ZnO conduction band. Additionally, according to electron lifetime studies, the Al-doped ZnO nanocubes act as a dielectric layer, enhancing the photogenerated charge extraction process due to the introduction of lattice defects, causing intermediate levels to obtain higher electron recombination resistance.

Enhanced photocatalytic performance of Bi-doped TiO2 under sunlight and UV light: mechanistic insights and comparative analysis.

Bismuth-doped metal oxides exhibit favourable photocatalytic features when exposed to both sunlight and UV light. In this approach, Bi0/TiO2 and Bi+3/TiO2 photocatalysts were prepared and their structural and optical properties are analysed using various characterization techniques. These developed photocatalysts were further tested for the photocatalytic elimination of Nitrobenzene in UV light and sunlight and compared with the performance of bare TiO2. The catalyst Bi+3/TiO2 performed better in UV light with 72.31% degradation, and 4.74 × 10-6mol.litre-1.min-1 initial rate of reaction. However, when exposed to sunlight, Bi0/TiO2 outperformed with 73.85% degradation, and 4.63 × 10-6mol.min-1 initial rate of reaction. This significant increase in photocatalytic activity of Bi0/TiO2 under sunlight could be accredited to increased light harvesting and enhanced efficiency in charge carrier separation, both of which were made possible by bismuth-induced surface plasmon resonance.

Controllable construction of direct Z-scheme Mo2C-CdxZn1−xIn2S4 heterojunction via defect-mediated modulation for enhanced visible-light photocatalysis

Direct Z-scheme semiconductor heterostructures possess fascinating merits for solar photocatalysis, including increased light harvesting, spatially isolated photogenerated charge carriers, and well-preserved strong redox capability. However, steering Z-scheme charge transfer of semiconductor heterojunction in a controllable manner is still a challenging task. In this work, unique direct Z-scheme Mo2C-CdxZn1−xIn2S4 heterojunction is constructed via a defect-mediated modulating strategy, where Cd-doping switches the charge transfer mode of Mo2C-CdxZn1−xIn2S4 heterojunction from type-I to Z-scheme through increasing S vacancies, up-shifting conduction band level, and narrowing bandgap of CdxZn1−xIn2S4 component. Moreover, the defect-induced Mo-S bond affords fast channels for built-in electric field-induced Z-scheme photo-electrons transporting from Mo2C conduction band to CdxZn1−xIn2S4 valence band, supporting by X-ray photoelectron spectroscopy, surface photovoltage spectroscopy, and radical testing results. Noticeably, under irradiation of visible light (λ > 400 nm), Mo2C-CdxZn1−xIn2S4 Z-scheme heterojunction displays an excellent and stable photocatalytic H2-evolving activity, reaching an outstanding H2 generation rate of 28.12 mmol·g−1·h−1 with the corresponding high apparent quantum efficiency of 21.1% at 400 nm, far surpassing that of Pt-loaded C0.25ZIS and most documented ZnIn2S4-containing photocatalysts. The present work could inspire the crafty design of efficient Z-scheme photocatalysts through defect-mediated heterostructure construction and energy band engineering.

Lavender-like S-scheme WO3/ZnIn2S4 heterostructures for boosting photocatalytic degradation of tetracycline

The environmentally friendly disposal of antibiotic wastewater has elicited widespread concern. Herein, lavender-like WO3/ZnIn2S4 heterostructures are constructed by in-situ anchoring ZnIn2S4 nanosheets onto WO3 nanorods and applied to the photocatalytic degradation of tetracycline (TC). When ZnIn2S4 and WO3 are successfully coupled at a molar ratio of 0.3:1, the resultant product WZ-3 exhibits optimal photocatalytic performance, which is 4.7 and 1.5 times higher than that of WO3 and ZnIn2S4, respectively. Such an improvement is originated from the enlarged specific surface area, increased light harvesting, and effective carriers separation facilitated by the formation of an S-scheme heterojunction, which is corroborated through density functional theory (DFT) calculations and experimental characterizations. Moreover, this study elucidates the mechanism governing TC degradation, including its degradation pathways.

Doping Sn4+ ionized cocatalyst in CdSe/S colloidal crystal for promoting photocatalytic CO2 reduction under visible light

The exploration of low-cost and efficient cocatalysts is vitally important for attaining reliable and affordable photocatalytic CO2 conversion. Here, it is found that post-transition metal ions (Sn4+) doped CdSe/S colloidal crystal can serve as effective photocatalyst for CO2 reduction under visible light, in which Sn4+ serves as an ionized cocatalyst. Specifically, Sn4+ doped CdSe/S colloidal crystal shows an improved and stable photocatalytic CO2 reduction performance with CO generation rate of 50.3 μmol h−1 and H2 generation rate of 7.8 μmol h−1 in the presence of triethanolamine as sacrificial agent. The improved photocatalytic activity can be ascribed to the increased light harvesting ability, enhanced CO2 adsorption capability and the improved surface charge transfer efficiency induced by Sn4+ dopant.

Z-scheme photocatalysis and photoelectrochemical platform with a Co3O4-CuO heterogeneous catalyst for the removal of water pollutants and generation of energy

Protection of the environment by increasing the use of renewable energy sources has become a global priority. The use of renewable resources to generate green energy and remove contaminants from water is an ongoing endeavor. Excellent dye degradation and water-splitting performances have been achieved using photocatalysis, a green technology, combined with the use of heterojunction nanocomposites fabricated with urchin-like and spherical morphologies (Co3O4:CuO). In this study, a one-pot solvothermal approach was used to fabricate a Co3O4–CuO heterojunction composite for use as a multifunctional substrate in dye degradation and photoelectrochemical (PEC) water splitting. For dye degradation, the weight percentage of CuO was adjusted against that of Co3O4; the fabricated CuO–Co3O4 (7.5 wt%) catalyst facilitated 82% degradation of azo dye within only 2 h. The improved catalyst was also used to degrade rhodamine B (76%), methylene blue (71%), and methyl orange (79%). Moreover, owing to its excellent photogenerated charge transfer kinetics and separation capability, the Co3O4–CuO photoelectrode exhibited a higher photocurrent density than the pristine materials in PEC water splitting. Linear sweep voltammetry under light illumination revealed that the photoresponse current of the multifunctional Co3O4–CuO composite was 6.05 mA/cm2 at a potential of 1.8 V (vs. Ag/AgCl), which is ∼2.01 and 3.1 times higher than those of pristine Co3O4 and CuO catalysts, respectively. The photocurrent response of the composite was 3.9 times higher than that under dark conditions. The substantial advantages offered by the fabricated composite over the pristine materials (Co3O4 and CuO), as well as its degradation and PEC water splitting capabilities, were attributed to the combined impact of numerous reactive sites, effective charge separation, increased light harvesting, and facile reactant transfer. Consequently, our research provides novel insights into the fabrication of unique binary nanocomposites with multiple applications and outstanding photocatalytic performance.

Enhanced Photoelectrochemical Performance in Engineered Interface 2D Metal Sulfide Heterostructures for Water Splitting

Photoelectrochemical water splitting (PEC) is a viable solution for addressing future environmental and energy concerns. However, due to the high cost of photoelectrodes and the limitations of sluggish kinetics, practical applications are limited. To achieve that goal, effective solutions are still needed to create low-cost photoelectrodes suited for PEC. Transistion metal sulfides (TMS) materials have a high potential for use as photoelectrodes due to their favorable and impressive properties1. The photoactivity of TMS is typically unlimited due to low reflection at the grain boundary. The individual atomic thin sheets with higher surface area compared to bulk materials allow for faster diffusion of photoinduced charge carriers primarily due to the less interface between their grains. Their lower interfacial contact resistance enables enhanced charge dynamics and, as a result, improved electrochemical reaction kinetics. When compared to other TMS, CdS has a direct bandgap and excellent photoactivity. However, its toxicity and photocorrosion make it unsuitable for long-term practical use. WS2 is well-known layered transition metal sulfide that has a 2D molybdenite structure. It is non-toxic in acidic/neutral solutions that are chemically stable. It has been demonstrated to be more stable against oxidation and photo corrosion than CdS, which is extensively employed in photocatalysis2. However, because of the recombination of photoinduced charge carriers, pure WS2 exhibits relatively poor photocatalytic efficiency and stability. As a result, combining WS2 based photoactive nanomaterials with other suitable materials has helped overcome this challenge. Transistion metal sulfides with acceptable band structures for heterostructure construction with WS2 may enable breakthroughs in photocatalytic and photo-electrochemical processes.The primary focus of this work is to construct heterostructures by combining CdS and WS2 and to investigate their role as photoanodes of semiconductor materials in PEC water splitting. In this work, we have synthesised heterostructures using a facile solution-reaction method and Successive Ionic Layer Adsorption Reaction deposition (SILAR) technique which is intrinsically cost effective and scalable3. The heterostructure is characterised by XRD, SEM and TEM. We also studied the performance enhancement of this heterostructure using Linear sweep voltammetry and Electrochemical impedance spectroscopy. Pristine WS2 and CdS showed photocurrent densities of 3 μA cm-2 and 20 μA cm-2. However, heterostructures formation led to much improved photocurrents. Photocurrent densities of 151 μA cm-2 were observed for WS2/CdS heterostructures respectively at 1.23 V vs RHE. The enhanced improvement in photoelectrochemical performance in the case of the heterostructures could be due to the following factors: (a) the intimate interaction of this unique heterostructure improves adhesion and lowers the photoinduced charge transfer barrier; (b) increased light harvesting capability; and (c) improved charge dynamics of photoinduced charge carriers due to proper band alignment. The current study paves the way for further research into the creation of metal sulfide heterostructures that generate analogous photoelectrode materials.Keywords: Photoelectrochemical water splitting, metal sulfides, photoelectrodes.

A novel strontium carbonate/strontium sulfate/strontium titanate composite with core shell structure for photocatalytic degradation of dyes

A core–shell structure SrSO4-SrCO3 (SSO-SCO) composite was synthesized with strontium titanate and ammonium carbonate. The SrTiO3-SrSO4-SrCO3 (TSC) composite with core–shell structure was obtained by adding strontium titanate into the mixture through hydrothermal method. The morphology, elemental composition and crystallinity of the catalyst were characterized by SEM, EDS, TEM and XRD analyses. The TSC composite exhibited excellent photocatalytic performance for the degradation of methylene blue dyes compared to the SrTiO3. The high catalytic efficiency was due to synergistic effect of the increased light harvesting and efficient transport of photogenerated electron and hole pairs in composites based on the results of UV–vis and PL and transient photocurrent response tests. Furthermore, ESR spectra showed that ·OH radicals and hole radicals were the main active species contributing to the excellent performance. Based on the photocatalytic results and ESR spectra, a photocatalytic mechanism for MB degradation was proposed.

Bi2 S3 -In2 S3 Heterostructures for Efficient Photoreduction of Highly Toxic Cr6+ Enabled by Facet-Coupling and Z-Scheme Structure.

The construction of Z-scheme photocatalyst materials mimicking the natural photosynthesis system provides many advantages, including increased light harvesting, spatially separated reductive and oxidative active sites and strong redox ability. Here, a novel Bi2 S3 nanorod@In2 S3 nanoparticle heterojunction photocatalyst synthesized through one-pot hydrothermal method for Cr6+ reduction is reported. A systematic investigation of the microstructural and compositional characteristics of the heterojunction catalyst confirms an intimate facet coupling between (440) crystal facet of In2 S3 and (060) crystal facet of Bi2 S3 , which provides a robust heterojunction interface for charge transfer. When tested under visible-light irradiation, the Bi2 S3 -In2 S3 heterojunction photocatalyst with 15% Bi2 S3 loading content achieves the highest Cr6+ photoreduction efficiency of nearly 100% with excellent stability, which is among the best-reported performances for Cr6+ removal. Further examination using optical, photoelectrochemical, impedance spectroscopy, and electron spin resonance spectroscopy characterizations reveal greatly improved photogenerated charge separation and transfer efficiency, and confirm Z-scheme electronic structure of the photocatalyst. The Z-scheme Bi2 S3 -In2 S3 photocatalyst demonstrated here presents promise for the removal of highly toxic Cr6+ , and could also be of interest in photocatalytic energy conversion.

(General Student Poster Session Winner - 3rd Place) Increased Light Harvesting in Photosystem 1-Based Biophotovoltaics with Artificial Antenna

Photosynthesis is a process used by algae and plants to convert light energy into chemical energy. In order to reduce the consumption of fossil fuels and curb global warming, the efficient use of sunlight by mimicking photosynthesis or directly using photosynthetic proteins is attracting attention. Photosynthetic proteins, which use highly complex and optimized processes that are impossible to reproduce, have been reportedly used in a variety of artificial applications such as biophotovoltaics, semi-artificial photosynthesis, biosensors, etc. These biomaterials are naturally abundant and pose no threat to the environment. In addition, the reaction center of a protein-pigment complex exhibits near-unity quantum efficiency attributable to spatial charge separation by multiple sequential electron-transfer pathways within the protein, which is a very attractive feature for researchers in the photoenergy-conversion field.Photosystem 1 (PS1), a photosynthetic protein-pigment complexes with high charge separation quantum efficiency, has been used as a material for biophotovoltaics. However, the photocurrent of these biophotovoltaic devices is not high because of their low spectral response. In nature, to compensate for the low spectral response of the reaction centers of photosynthetic protein-pigments, förster resonance energy transfer (FRET) is used by the light-harvesting (LH) antennas. In this work, we have integrated an artificial LH antenna into a PS1-based biophotovoltaic in the form of a fluorescent dye, perylene di-imide derivative to expand the spectral response.The biophotovoltaics were fabricated in the same way as dye-sensitized solar cells (DSSCs); a two-electrode sandwich cell was prepared with a stained-TiO2 photoanode, a Pt counter electrode, and a triiodide/iodide-based ionic liquid electrolyte. The fabrication of the stained-TiO2 photoanode was carried out by sequential immersion in two solutions of artificial LH antenna and PS1. The incident photon-to-current conversion efficiency (IPCE) spectra and the photocurrent-density–voltage (J–V) curve under AM 1.5 G (100 mW cm-2) were measured.When PTCDI was used as artificial LH antenna, the magnitude of the IPCE spectrum is significantly enhanced in the range of 450–750 nm, and the photocurrent increased [1]. This range matches the absorption range of the PTCDI/PS1-assembled electrode; thus, the high-intensity part of the solar spectrum can be used to generate electric power. We measured the fluorescence spectra of the stained ZrO2 electrode. According to the fluorescence spectrum of the PTCDI/PS1-assembled ZrO2 electrode, a decrease in PTCDI fluorescent intensity at around 670 nm was observed. Time resolved fluorescence measurements show that the fluorescence of PTCDI decays faster in the presence of PS1 than in the absence. Moreover, PTCDI was previously reported to be quenched in proportion to the concentration of PS1, following the Stern–Volmer equation [2]. These results can be interpreted as evidence that the photons absorbed at PTCDI were transferred to PS1 via FRET.The electrodes fabricated in this study are considered to be a simple stacked structure of artificial LH antenna and PS1. The advantage of this method is that there are many antennas on the electrode around PS1. Therefore, we believe that the electrode lead to more efficient not only in biophotovoltaics but also in other bio-applications.[1] Y. Takekuma, H. Nagakawa, T. Noji, K. Kawakami, R. Furukawa, M. Nango, N. Kamiya, and M. Nagata ACS Applied Energy Materials, 2019, 2(6), 3986–3990.[2] H. Nagakawa, A. Takeuchi, Y. Takekuma, T. Noji, K. Kawakami, N. Kamiya, M. Nango, R. Furukawa and M. Nagata Photochem. Photobiol. Sci., 2019, 18, 309–313.

A coral-like hematite photoanode on a macroporous SnO2: Sb substrate for enhanced photoelectrochemical water oxidation

Oxygen evolution over semiconductor photoanodes plays a decisive role in water splitting via photoelectrochemical (PEC) process. While the hematite photoanode with a photocurrent threshold of 600 nm is promising for practical PEC water oxidation, it still suffers from the small minority carrier diffusion length, which makes it difficult to realize adequate light absorption and efficient charge separation concurrently. To address this issue, hematite nanorods were grown on macroporous SnO2:Sb substrates, forming a coral-like hematite (ATO-Fe2O3) photoanode. The ATO-Fe2O3 photoanode exhibited a 150 mV cathodic shift of onset relative to Fe2O3 nanorods directly on planar SnO2:F (FTO-Fe2O3). The photocurrent density reached 1.32 mA cm−2 at 1.23 V vs. RHE, approximately 8.8 times higher than FTO-Fe2O3, and it was further increased to 1.81 mA cm−2 after passivation with a thin TiO2 overlayer. The improved photocurrent was attributed to the increased light harvesting, reduced charge transfer resistance (Rct), and smaller contact area of oxygen bubble to hematite photoanode. Our research confirmed the effectiveness of macroporous ATO templated coral-like morphology on balancing the adequate light absorption and efficient charge separation issues of hematite photoanodes. This research may also be applicable to other semiconductor photoanodes for high-efficiency PEC water splitting.

Modeling the Role of LHCII-LHCII, PSII-LHCII, and PSI-LHCII Interactions in State Transitions

The light-dependent reactions of photosynthesis take place in the plant chloroplast thylakoid membrane, a complex three-dimensional structure divided into the stacked grana and unstacked stromal lamellae domains. Plants regulate the macro-organization of photosynthetic complexes within the thylakoid membrane to adapt to changing environmental conditions and avoid oxidative stress. One such mechanism is the state transition that regulates photosynthetic light harvesting and electron transfer. State transitions are driven by changes in the phosphorylation of light harvesting complex II (LHCII), which cause a decrease in grana diameter and stacking, a decrease in energetic connectivity between photosystem II (PSII) reaction centers, and an increase in the relative LHCII antenna size of photosystem I (PSI) compared to PSII. Phosphorylation is believed to drive these changes by weakening the intramembrane lateral PSII-LHCII and LHCII-LHCII interactions and the intermembrane stacking interactions between these complexes, while simultaneously increasing the affinity of LHCII for PSI. We investigated the relative roles and contributions of these three types of interaction to state transitions using a lattice-based model of the thylakoid membrane based on existing structural data, developing a novel algorithm to simulate protein complex dynamics. Monte Carlo simulations revealed that state transitions are unlikely to lead to a large-scale migration of LHCII from the grana to the stromal lamellae. Instead, the increased light harvesting capacity of PSI is largely due to the more efficient recruitment of LHCII already residing in the stromal lamellae into PSI-LHCII supercomplexes upon its phosphorylation. Likewise, the increased light harvesting capacity of PSII upon dephosphorylation was found to be driven by a more efficient recruitment of LHCII already residing in the grana into functional PSII-LHCII clusters, primarily driven by lateral interactions.

Doping Carbon Nitride Quantum Dots into Melamine‐Silver Matrix: An Efficient Photocatalyst with Tunable Morphology and Photocatalysis for H2O2 Evolution under Visible Light

AbstractCarbon nitride quantum dots (CNQDs) were doped into melamine (MA) and silver (Ag) matrix yielding CNQDs@MA−Ag nanocomposites by the supramolecular self‐assembly route. To our surprise, the resulting mesoporous nanocomposites could present different morphologies (i. e., nanowires, nanoflowers, and nanosheets) and especially tunable visible‐light photocatalysis performances depending on the percentages of CNQDs used. It was discovered that the CNQDs@MA−Ag ones with the pinecone‐like structure (containing 30 % CNQDs) could exhibit the strongest visible‐light photocatalysis for splitting water to yield H2O2 with a production efficiency of 39.82 μmol ⋅ g−1 h−1, which is more than ten‐fold higher than that of CNQDs alone. Herein, the nano‐scaled Ag could facilitate the increased light harvesting and the separation as well as transmission of electron‐hole pairs of CNQDs resulting in the enhanced visible‐light photocatalysis of nanocomposites. More importantly, the pinecone‐like ones might additionally enable more exposed active sites of photocatalysis and larger mesoporous specific area of contacting dissolved oxygen in water, leading to the higher photocatalytic efficiency of H2O2 generation. This CNQDs‐based fabrication strategy may open a new door towards the design of a variety of photocatalysts with different morphologies and tunable photocatalysis performances for the efficient splitting water toward H2O2 evolution under sunlight.

Uniform dispersion of CuO nanoparticles on mesoporous TiO2 networks promotes visible light photocatalysis

Here, we focus our efforts on synthesizing a uniform dispersion of CuO nanoparticles on mesoporous TiO2 networks for the first time. H2PtCl6 was added through a photocatalytic reaction to produce 0.5% Pt/CuO–TiO2 nanocomposites. XRD patterns confirmed that the prepared TiO2 formed the anatase phase. TEM images showed close contacts between CuO and TiO2 with 5–10 nm particle sizes. One of the advantages of the synthesized mesoporous CuO–TiO2 nanocomposites was the high pore volume (0.540 cm3 g−1) and large surface area (300 m2 g−1). The H2 evolution over the mesoporous 3 wt% CuO–TiO2 nanocomposites using a glucose hole scavenger [10 vol%] was determined to be ~13000 μmol/g, a value that was 1300 times greater than that of mesoporous TiO2. The H2 evolution rate was increased by up to 1300 and 20 times for 3 wt% CuO–TiO2 and 0.1 wt% CuO–TiO2 nanocomposites, respectively, compared with that of mesoporous TiO2. The increase in H2 evolution over mesoporous CuO–TiO2 nanocomposites was explained by the increased light harvesting capacity, high glucose molecule diffusion and efficient charge carrier separation. Moreover, the construction of a heterostructure with a p–n CuO–TiO2 heterojunction expedited the separation of charge carriers and promoted the evolution of H2. In addition, H2 evolution was substantially increased by the synergistic effects of Pt and CuO on the mesoporous TiO2 networks. Photoelectrochemical and photoluminescence measurements were employed to prove the H2 evolution mechanism over the CuO nanoparticles deposited on the mesoporous TiO2 networks.

Advanced partial nucleation for single-phase FA0.92MA0.08PbI3-based high-efficiency perovskite solar cells

To date, extensive research has been carried out, with considerable success, on the development of high- performance perovskite solar cells (PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixed-cation perovskite FA x MA1− x PbI3 (formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FA x MA1− x PbI3 films contain a high percentage of MA+ and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-PbI2-DMSO (DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.

TiO2/Cu2(OH)2CO3 nanocomposite as efficient antimicrobials for inactivation of crop pathogens in agriculture.

TiO2/Cu2(OH)2CO3 nanocomposite were synthesized via a simple in-situ precipitation process, which was applied as efficient antimicrobials for the inactivation of Escherichia coli (E. coli) and Fusarium graminearum (F. graminearum) under simulated solar light. With optimum Cu2(OH)2CO3 amount of 1.8 mol%, the TiO2/Cu2(OH)2CO3 nanocomposite presented the highest antimicrobial activities against E. coli and F. graminearum, and achieved complete inactivation in 80 min, which was far better than that of bare TiO2. The boosted photocatalytic disinfection efficiency was ascribed to the increased light harvesting and efficient charge transfer and separation in the TiO2/Cu2(OH)2CO3 nanocomposite, which resulted in more efficient generation of •OH and •O2- that played important role in the photocatalytic inactivation process. Our work revealed that TiO2/Cu2(OH)2CO3 composite was a promising antimicrobial agent for prevention of pathogenic fungal or bacterial infections in crop protection.

Morphology luminescence and photovoltaic performance of lanthanide-doped CaWO4 nanocrystals

Multifunctional materials have attracted recent attention due to their various applications in many fields. In this work, CaWO4 nanocrystals were prepared by a hydrothermal method. Nanoparticles, nanowires, and micro-sized structures were obtained by controlling the reaction temperature, Ca2+-to-WO42− ratio and type of dopant. The influence of rare earth ions on the morphology and luminescence properties was investigated. Upconversion and downconversion luminescence behaviors showed CaWO4 to be an excellent host for rare earth doping. CaWO4:Er3+ nanowires were also used in dye-sensitized solar cells (DSSCs) to improve device performance. Increased light harvesting caused by improved dye loading capacity and enhanced light scattering led to improved cell efficiency. Moreover, reduced charge recombination due to the additional energy levels of CaWO4:Er3+ was another reason for the improved cell efficiency. Therefore, in this work, we demonstrated the synthesis of CaWO4 nanocrystals and the control of their morphology and luminescence by rare earth doping, which has significant future applications in lighting and display. The applications in DSSCs provide a new strategy to achieve high-performance solar cells by using nanocrystals via increased light harvesting and reduced charge recombination.

Interfacial growth of the optimal BiVO4 nanoparticles onto self-assembled WO3 nanoplates for efficient photoelectrochemical water splitting

Photoelectrochemical water splitting is the most efficient green engineering approach to convert the sun light into hydrogen energy. The formation of high surface area core-shell heterojunction with enhanced light-harvesting efficiency, elevated charge separation, and transport are key parameters in achieving the ideal water splitting performance of the photoanode. Herein, we demonstrate a first green engineering interfacial growth of the BiVO4 nanoparticles onto self-assembled WO3 nanoplates forming WO3/BiVO4 core-shell heterojunction for efficient PEC water splitting performance. The three different WO3 nanostructures (nanoplates, nanobricks, and stacked nanosheets) were self-assembled on fluorine doped tin oxide glass substrates via hydrothermal route at various pH (0.8–1.2) of the solutions. In comparison to nanobricks and stacked nanosheets, WO3 nanoplates displayed considerably elevated photocurrent density. Moreover, a simple and low cost green approach of modified chemical bath deposition technique was established for the optimal decoration of a BiVO4 nanoparticles on vertically aligned WO3 nanoplates. The boosted photoelectrochemical current density of 1.7 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination was achieved for the WO3/BiVO4 heterojunction which can be attributed to a suitable band alignment for the efficient charge transfer from BiVO4 to WO3, increased light harvesting capability of outer BiVO4 layer, and high charge transfer efficiency of WO3 nanoplates.

Facile Synthesis of Heterojunctioned ZnO/Bi2S3 Nanocomposites for Enhanced Photocatalytic Reduction of Aqueous Cr(VI) under Visible-Light Irradiation

Heterojunctioned ZnO/Bi2S3 nanocomposites were prepared via a facile solvothermal method. The obtained photocatalysts were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), and Photoelectrochemical and Photoluminescence spectroscopy (PL), respectively. The results showed that ZnO/Bi2S3 composites exhibited the sandwiched-like structure, where ZnO nanoparticles were randomly embedded between Bi2S3 nanoflakes. The performance of photocatalytic Cr(VI) reduction under visible light indicated that ZnO/Bi2S3 composites exhibited high-efficiency photocatalytic activity in comparison with either Bi2S3 or ZnO. The 5%-ZnO/Bi2S3 photocatalyst removed 96% of Cr(VI) within 120 min at 20 mg/L initial concentration of Cr(VI). The enhanced performance of ZnO/Bi2S3 photocatalysts could be ascribed to the increased light harvesting and the effective separation and transfer of the photogenerated charge carriers across the heterojunction interface of the ZnO/Bi2S3 composite. This work could pave the way for the design of new hetero-structured materials and has great potential in environmental remediation.

Porphyrin-containing Polyimide with Enhanced Light Absorption and Photocatalysis Activity.

A series of porphyrin-containing polyimide (PI) photocatalysts were synthesized by a one-step solvothermal method. Characterization results revealed that porphyrin was uniformly coupled into the PI framework through covalent bonding and the visible-light absorption was greatly improved. The photodegradation activity of porphyrin-containing PIs for methyl orange (MO) under visible light was enhanced significantly, with the highest pseudo-first-order rate constant 35 times higher than that of neat porphyrin and 10 times higher than that of porphyrin-free PI. The enhancement is mainly attributed to an increased light harvesting accompanied by a varied HOMO level, which was clarified by control experiments, characterizations and theoretical calculations. This work provides an insight into multiple effects of dye molecules in dye-containing heterogeneous photocatalysts.