Strong Visible Light Absorption Research Articles

Large-Scale Synthesis of p–n Heterojunction Bi2O3/TiO2 Nanostructures as Photocatalysts for Removal of Antibiotics under Visible Light

Although photocatalysis has been proved to be a promising technology in solving various environmental problems, the preparation of visible light-driven photocatalysts on a large scale in a simple and sustainable manner still remains a technical challenge. Here, we demonstrate a simple one-pot method for the large-scale synthesis of a novel Bi2O3/TiO2 visible light-driven photocatalyst by coupling low-cost TiO2 with strong visible-light absorption of Bi2O3. The as-synthesized Bi2O3/TiO2 photocatalyst exhibits efficient charge separation due to the formation of a p–n heterojunction. Additionally, the porous nanostructure of Bi2O3/TiO2 provides high surface area and abundant active sites, realizing the complete degradation (100%) of tetracyclines under visible light (λ > 420 nm), which successfully breaks through the bottleneck of incomplete degradation of tetracyclines under visible light irradiation for most of the reported photocatalysts. Notably, since our method is based on the one-pot synthesis without any pretreatment procedure for the precursors of Bi2O3 and TiO2, it is very suitable for the development of large-scale synthesis by using a big reactor, producing up to 23.9 g of Bi2O3/TiO2 nanocatalyst in a single synthesis, which indicates its considerable potential for further scale-up production. Therefore, this study opens a new window for the large-scale synthesis of other visible light-driven photocatalysts with excellent photocatalytic performances.

Highly Efficient Ir(III)-Coumarin Photo-Redox Catalyst for Synergetic Multi-Mode Cancer Photo-Therapy.

Four photo-catalysts of the general formula [Ir(CO6/ppy)2 (L)]Cl where CO6=coumarin 6 (Ir1-Ir3), ppy=2-phenylpyridine (Ir4), L=4'-(3,5-di-tert-butylphenyl)-2,2' : 6',2''-terpyridine (Ir1), 4'-(3,5-bis(trifluoromethyl)phenyl)-2,2' : 6',2''-terpyridine (Ir2 and Ir4), and 4-([2,2' : 6',2''-terpyridin]-4'-yl)-N,N-dimethylaniline (Ir3) were synthesized and characterized. These photostable photo-catalysts (Ir1-Ir3) showed strong visible light absorption between 400-550 nm. Upon light irradiation (465 and 525 nm), Ir1-Ir3 generated singlet oxygen and induced rapidly photo-catalytic oxidation of cellular coenzymes NAD(P)H. Ir1-Ir3 showed time-dependent cellular uptake with excellent intracellular retention efficiency. Upon green light irradiation (525 nm), Ir2 provided a much higher photo-index (PI=793) than the clinically used photosensitizer, 5-aminolevulinicacid (5-ALA, PI>30) against HeLa cancer cells. The observed necro-apoptotic anticancer activity of Ir2 was due to the Ir2 triggered photo-induced intracellular redox imbalance (by NAD(P)H oxidation and ROS generation) and change in the mitochondrial membrane potential. Remarkably, Ir2 showed in vivo photo-induced catalytic anticancer activity in mouse models.

Direct Z-scheme-based novel cobalt nickel tungstate/graphitic carbon nitride composite: Enhanced photocatalytic degradation of organic pollutants and oxidation of benzyl alcohol

Designing a photocatalyst with strong redox ability and broad absorption of visible light is challenging in the field of photocatalysis. In this study, a series of novel Z-scheme-based Co x Ni 1−x WO 4 /g-C 3 N 4 (x = 0, 0.2, 0.5, 0.8 and 1) photocatalysts are synthesized with a view to increasing their redox abilities and improve their photocatalytic activities under broad absorption of visible light. The physicochemical properties are investigated, and the data show that an intimate stable heterojunction is formed between the bimetallic tungstate (CoNiWO 4 ) and g-C 3 N 4 (g-CN). Bifunctional properties of the synthesized catalysts are assayed by studying the decomposition of rhodamine B (RhB), bisphenol A (BPA), and selective conversion of benzyl alcohol (BA) to benzaldehyde (BDA). The composite material containing 1:1 molar ratio of Co/Ni shows the highest activity towards the degradation of RhB (99.8%) and BPA (99.32%), and the conversion of BA to BDA (86.96%), each at 1 g/ L -dose. The well-matched band structure between CoNiWO 4 and g-CN facilitates the formation of a Z-scheme charge transfer path, which prolongs the life time of the photoinduced charge carriers with high redox power, thus enhancing the photocatalytic activity. An intensive study of the mechanism proves that the degradation is driven by the hydroxyl ( • OH) and superoxide ( • O 2 - ) radicals, indicating that CoNiWO 4 /g-CN follows the Z-scheme charge transfer pathway. The current study has shown the superior photocatalytic activity among all tungstate-based hybrid photocatalytic materials for the degradation of complex organic pollutants, and selective transformation of BA to BDA. The findings in this study provide a new direction to the development of an efficient direct Z-scheme Co-Ni bimetallic tungstate-based photocatalyst for several redox reactions, especially mineralization of recalcitrant aqueous organic compounds. • A novel direct Z-scheme-based CoNiWO 4 /g-CN heterojunction is synthesized. • Photocatalytic degradation of RhB and BPA, and oxidation of BA are investigated. • Material with 1:1 Co-Ni molar ratio shows the best photocatalytic activity. • • O 2 - and • OH are the main ROS in the photocatalytic degradation of aqueous pollutants. • A direct Z-scheme charge transfer mechanism over CoNiWO 4 /g-C 3 N 4 is proposed.

Strain engineering of electronic and optical properties of monolayer diboron dinitride

We studied the effect of strain engineering on the electronic, structural, mechanical, and optical properties of orthorhombic diboron dinitride (o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$) through first-principles calculations. The 1.7-eV direct band gap observed in the unstrained o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ can be tuned up to 3 eV or down to 1 eV by applying 12% tensile strain in armchair and zigzag directions, respectively. Ultimate strain values of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ were found to be comparable with that of graphene. Our calculations revealed that the partial alignment of the band edges with the redox potentials of water in pristine o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ can be tuned into a full alignment under the armchair and biaxial tensile strains. The anisotropic charge carrier mobility found in o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ prolongs the average lifetime of the carrier drift, creating a suitable condition for photoinduced catalytic reactions on its surface. Finally, we found that even in extreme straining regimes, the highly anisotropic optical absorption of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ with strong absorption in the visible range is preserved. Having strong visible light absorption and prolonged carrier migration time, we propose that strain engineering is an effective route to tune the band gap energy and band alignment of o-${\mathrm{B}}_{2}{\mathrm{N}}_{2}$ and turn this two-dimensional material into a promising photocatalyst for efficient hydrogen production from water splitting.

Aminosilicate modified zinc oxide Nanorod-GO nanocomposite for DSSC photoanodes

Amine-functionalized ZnO nanorods@graphene oxide (ZnO-NR/NH2/GO) nanocomposites prepared by a facile solution route have been investigated through X-ray diffraction, diffuse reflectance spectra, Raman spectra, scanning electron microscopy and transmission electron microscopy. The amine-functionalized ZnO-NR/NH2/GO-2 nanocomposite exhibits very strong visible light absorption. Dye-sensitized solar cell (DSSC) made of ZnO-NR/NH2/GO-2 nanocomposite (with optimum 2 wt % GO) photoanode delivers a power conversion efficiency (PCE) of 3.76% which is much higher than the efficiency of unmodified ZnO-NR/GO photoanodes based DSSC (2.27%). The enhancement of PCE is primarily caused by the increased current density, attributed to the incorporation of aminosilicate and GO on the surface of ZnO-NRs which facilitates rapid transfer of electron from conduction band of ZnO to conducting surface of FTO. This diminished recombination of photogenerated electrons and holes improve the electron transfer at the photoanode/electrolyte interfaces.

Enhanced degradation of carbamazepine by BiOX (Cl, Br, I) composite photocatalysts under simulated solar light irradiation

To use solar energy effectively, BiOX (Cl, Br, I) nanosheets with reasonable band gap structure were prepared by ultrasonic assisted hydrothermal method. The prepared BiOX (Cl, Br, I) nanosheets removed 90% of CBZ within 5 min, showing rapid degradation kinetic of 0.3858 min−1. The improved photocatalytic activities can be due to the reduced recombination of photoinduced electron-hole pairs, strong visible-light absorption ability, large surface area and pore. Radicals experiments indicated that the BiOX (Cl, Br, I) generated main holes (h+) and minor electrons (e−) to degrade CBZ. These results demonstrated the good feasibility of BiOX (Cl, Br, I) nanosheets in the degradation of CBZ under simulated solar light irradiation.

Microtubular carbonized cotton fiber modified g-C3N4 for the enhancement of visible-light-driven photocatalytic activity

The combination of graphitic carbon nitride (g-C3N4) and carbonized material is a promising strategy to improve g-C3N4’s visible light absorption and charge separation efficiency. Herein, a carbonized cotton fiber (CCF) modified pure g-C3N4 (PCN/CCF) composite photocatalyst is prepared by a one-step calcination method for visible-light-driven photocatalytic. Due to CCF excellent electronic transmission and strong absorption of visible light, the green-cheap carbonized cotton fiber in the composite photocatalyst (PCN/CCF) can effectively enhance charge separation efficiency and enhances the visible light absorption of PCN. And the degradation efficiency of PCN/CCF-6 to methyl orange can reach 90% in 1 h under visible light irradiation. The photodegradation constant of PCN/CCF-6 is 0.03105 min−1, which is 8 times that of bulk carbon nitride (BCN) and twice that of the pure g-C3N4 (PCN). This catalyst also shows excellent degradation performance against other pollutants (Rh B, TC). PCN/CCF provide an effective way for carbon-based materials to assist high-efficiency photocatalytic degradation of organic pollutants.

Triazine‐Functionalized Silsesquioxane‐Based Hybrid Porous Polymers for Efficient Photocatalytic Degradation of Both Acidic and Basic Dyes under Visible Light

AbstractFour triazine‐functionalized silsesquioxane‐based hybrid porous polymers (TSHPPs) were synthesized by Heck reaction of octavinylsilsesquioxane (OVS) with brominated phenyl or thiophene substituted triazine monomers. These hybrid polymers offered good thermal stability, high specific surface areas (up to 555 m2 g−1), strong visible light absorption, and adjustable fluorescence properties. The materials showed high photocatalytic activity for the degradation of both acidic and basic dyes without additional oxidation agents or pH adjustments. Exposing to natural light, at a very low concentration of TSHPPs (0.2 mg mL−1), dyes with a concentration of up to 1000 ppm can be completely decolorized. After five consecutive iterations of degradation dyes, TSHPPs still showed good regenerability. This work provides an efficient method for the construction of photo‐responsive porous materials for solar‐to‐chemical energy conversion and demonstrates their potential as green and sustainable environment‐friendly catalysts.

Synthesizability and Properties of Metastable Semiconductors for Solar Energy Conversion

Metastable semiconductors in many chemical systems have been discovered that have desirable semiconductor properties for driving fuel-producing redox reactions from water and sunlight, such as strong visible light absorption, optimal band-edge energies, extreme defect tolerance, and enhanced carrier mobilities and charge separation. These properties are intimately related to their metastable nature, i.e., their crystalline structures and compositions lead to thermodynamic instabilities. New results will be presented that demonstrate flux-mediated synthetic routes to new metastable n-type Sn(II)-titanates and p-type Cu(I)-niobates. These semiconductors possess some the smallest known visible-light band gaps that also maintain suitable conduction and valence band energies for the photocatalytic reduction and oxidation of water to molecular hydrogen and oxygen, respectively. Their electronic structures also show advantageous features for solar energy conversion, such as small bandgaps, high band dispersion and defect tolerance. These characteristics are intimately related to their metastability and kinetic stabilization, which can be achieved via solid solutions that inhibit phase segregation. Thus, the solid-solution semiconductors Cu5(Ta1-x Nb x )11O30 and (Ba1-x Sn x )(Zr1-yTi y )O3 have been prepared using flux-mediated synthesis methods. Their band gaps, band edge energies and photocatalytic activities for the production of molecular hydrogen and molecular oxygen are found to be a sensitive function of their chemical compositions.

Strong Visible Light Absorption and Abundant Hotspots in Au-Decorated WO3 Nanobricks for Efficient SERS and Photocatalysis.

Metal/semiconductor hybrids show potential application in fields of surface-enhanced Raman spectroscopy (SERS) and photocatalysis due to their excellent light absorption, electric field, and charge-transfer properties. Herein, a WO3-Au metal/semiconductor hybrid, which was a WO3 nanobrick decorated with Au nanoparticles, was prepared via a facile hydrothermal method. The WO3-Au hybrids show excellent visible light absorption, strong plasmon coupling, high-performance SERS, and good photocatalytic activity. In particular, on sensing rhodamine B (RhB) under 532 nm excitation, bare WO3 nanobricks have a Raman enhancement factor of 2.0 × 106 and a limit of detection of 10–8 M due to the charger-transfer property and abundant oxygen vacancies. WO3-Au metal/semiconductor hybrids display a largely improved Raman enhancement factor compared to pure Au and WO3 components owing to the synergistic effect of electromagnetic enhancement and charge transfer. The Raman enhancement factor and limit of detection are further improved, reaching 5.3 × 108 and 10–12 M, respectively, on increasing the content of Au to 2.1 wt %, owing to the strong plasmon coupling between the Au nanoparticles. Additionally, the WO3-Au hybrids also exhibit excellent photocatalytic activity toward degradation of RhB under visible light irradiation. WO3-Au (2.1 wt %) possesses the fastest photocatalytic rate, which is 6.1 and 2.0 times that of pure WO3 nanobricks and commercial P25, respectively. The enhanced photocatalytic activity is attributed to the strong plasmon coupling and the efficient charge transfer between Au and WO3 nanobricks. The as-prepared materials show great potential in detecting and degrading pollutants in environmental treatment.

Flexible Metal Halide Perovskite Photodetector Arrays via Photolithography and Dry Lift‐Off Patterning

Metal halide perovskites draw increasing attention as photodetector materials due to their strong visible light absorption and resulting photocurrent. The development of efficient fabrication routes to realize high‐resolution perovskite pixel arrays is critical to enable practical devices. Herein, a dry lift‐off process to fabricate methylammonium lead iodide (MAPbI3) pixels on different substrates is reported, with a resolution down to 5 μm. Accordingly, 8 × 10 photodetector arrays are fabricated on both glass and flexible polyethylene terephthalate (PET). These arrays show a sensitive photoresponse over a broad wavelength range from 320 to 760 nm. Moreover, when encapsulated by a Parylene‐C overlayer, the photodetector arrays on glass substrate show remarkable air stability, without noticeable performance loss after 10 days in ambient air, and the flexible photodetector arrays on PET substrate show excellent bending tolerance, retaining nearly 95% of the response after 170 bending cycles.

Boosting interfacial charge separation and photocatalytic activity of 2D/2D g-C3N4/ZnIn2S4 S-scheme heterojunction under visible light irradiation

It was an effective strategy to improve photocatalytic degradation performance by constructing step-scheme (S-scheme) heterojunction photocatalysts with superior photo-redox capacity and high charge transfer efficiency. In this study, two-dimensional/two-dimensional (2D/2D) S-scheme g-C3N4/ZnIn2S4 (CN/ZIS) heterojunction with different mass ratios were synthesized by the hydrothermal method. Transmission electron microscopy (TEM) analysis showed that ZnIn2S4 nanosheets with an average size of ~20 nm were coupled on the surface of ultra-thin graphitic carbon nitrogen (g-C3N4) nanosheets, which can effectively increase the contact area. UV–vis diffuse reflectance spectra (DRS), Photoluminescence spectra (PL) and photochemical tests showed that CN/ZIS had strong visible light absorption ability and photo-generated carriers transfer ability. Under visible light irradiation, CN/ZIS-10 degraded 93.41% of tetracycline (TC), which was 1.38 times than that of pristine g-C3N4. Moreover, the photocatalytic activity of CN/ZIS-10 was almost no change after five cycles. The S-scheme mechanism of CN/ZIS-10 was explored through electron spin response (ESR) and capture experiments of active species. In conclusion, this work provided a reasonable example for the construction of g-C3N4-based S-scheme heterojunction.

Constructing electrostatic self-assembled ultrathin porous red 2D g-C3N4/Fe2N Schottky catalyst for high-efficiency tetracycline removal in photo-Fenton-like processes

The traditional heterogeneous photo-Fenton reaction was mainly restricted by the fewer surface-active sites, low Fe3+/Fe2+ transformation and H2O2 activation efficiency of catalyst. This work designed and fabricated the efficient photo-Fenton Schottky catalysts via a facile electrostatic self-assembly of metallic Fe2N nanoparticles scattering on the surface of red g-C3N4 (ultrathin porous oxygen-doped 2D g-C3N4 nanosheets). The porous morphology and exceptional electrical structure of red g-C3N4 endowed more active sites and facilitated the photoexcited charge separation. Benefitting from the Schottky effect and unique dimensional coupling structure, the strong visible light absorption and fast spatial charge transfer were realized in the Schottky junction system. More strikingly, Fe2N as an efficient co-catalyst was in favor of the trap and export of e-, leading to the Fe3+/Fe2+ transformation and H2O2 activation during the photo-Fenton process. Accordingly, the as-prepared catalysts revealed outstanding activity in photo-Fenton like degradation of tetracycline (TC) although under 5 W white LED light irradiation. Furthermore, the reasonable degradation pathway of TC and corresponding toxicity of the intermediates, as well as the photo-Fenton catalytic mechanism were interpreted and discussed in detail. This study would be a great aid in the development of various Schottky catalysts for heterogeneous photo-Fenton-based environmental remediation systems.

Bidirectional sensitization in Ruthenium(II)-antenna dyad beyond energy flow of biological model for efficient photosynthesis

In natural photosynthetic system, sunlight is harvested by chlorophyll, subsequent funneling of the excitation energy to redox centers to trigger redox reaction. In contrast, the functions of light absorption, intersystem crossing and redox reaction were integrated into a single species (i.e. Ru(bpy)32+) in traditional catalytic system. Inspired by nature, we explore a strategy to introduce the strong absorbing dyes into Ru redox center and regulate their excited states by increasing the π-conjugation of dyes to afford a series of Ru(II) complexes-chromophore dyads (Ru-1 – Ru-5). Experimental and theoretical investigations reveal a forward singlet energy transfer following a backward triplet energy transfer between chromophore/Ru center in Ru-5, presenting a bidirectional sensitization, which not only achieve the functional separation among components in photosensitizer but also promote the efficient collaboration between Ru(II) center and chromophore. Remarkably, Ru-5 exhibited a strong visible light absorption at 463 nm (ε = 50500 M−1cm−1) and its triplet lifetime reached to 122.5 μs, over 400 times longer than the single component complex Ru-1. These advantages enable Ru-5 a significantly higher catalytic activity than the typical Ru(bpy)32+ for both energy- and electron-transfer reactions. This work opens up a new avenue to improve photosensitization for efficient photosynthesis by learning from nature.

Synergistic effect of photo-reduced Ni–Ag loaded g-C3N4 nanosheets for efficient visible Light‐Driven photocatalytic hydrogen evolution

A heterogenous ternary Ni and Ag co-modified g-C3N4 nanocomposite is designed and fabricated using a photoreduction approach for photo-catalytic hydrogen production from methanol-water mixture. Ternary nanocomposite consisting of Ni–Ag co-deposited onto g-C3N4 was successfully fabricated and uniformly distributed, therefore, exhibited strong visible-light absorption and efficient charge carrier separation due to synergistic effect throughout the ternary composite. The nanocomposite with varying amounts of nickel and silver, play an important role to maximize the photoactivity with the optimized 3Ni–1Ag/CN sample delivering H2 of 2137.5 μmolg−1h−1, which is 16.13, 1.42 and 1.52 folds greater than using CN, 3Ni/CN and 3Ag/CN, respectively. This proves that semiconductor composition ratio is important in achieving a successful p-n junction and efficient charge separation and transfer in the ternary composite. The performance of optimized Ni–Ag/CN was further enhanced using photo-reduction method. The highest H2 yield of 5740 μmolg−1 is achieved over the photo-reduced Ni–Ag/CN-R nanocomposite which is 1.25 folds higher than non-photo-reduced composite. This improvement can be accredited to the formation of good p-n junction between the semiconductors in the ternary composite and due to the formation of photo-reduced Ag which acts as electron sinks which leads to improved charge separation. Furthermore, increasing catalyst loading increases the H2 production rate and methanol-water mixture gave the highest H2 production rate. The findings of this study would be beneficial for future hydrogen generation and implementation within newer sustainable systems.

Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

Electron Spin Dynamics of the Intersystem Crossing of Triplet Photosensitizers That Show Strong Absorption of Visible Light and Long-Lived Triplet States

Triplet Photosensitizers Showing Strong Absorption of Visible Light and Long-Lived Triplet Excited States and Application in Photocatalysis: A Mini Review

Triplet photosensitizers (PSs) have been studied as photocatalysts in photocatalytic H2 evolution by water splitting and photoredox catalytic synthetic organic reactions, etc. The applications share common features that the photocatalysts (triplet PSs) harvest the photoexcitation energy, then undergo intersystem crossing (ISC), and finally initiate the electron transfer or triplet energy transfer, which are intermolecular processes in most cases. Thus, triplet PSs showing a strong visible-light-harvesting ability and long triplet excited state lifetimes are desired because they can enhance the above intermolecular processes. The conventional transition metal complexes (i.e., Ru(bpy)3X2 or Ir(ppy)3) have been widely used; however, these complexes are not satisfactory due to their weak absorption of visible light and short triplet excited state lifetimes. To a large extent, the photophysical property of these complexes is due to the low-lying metal-to-ligand charge transfer (MLCT) state, the S0 → 1MLCT transition is weakly allowed, and a strong heavy atom effect exists for the 3MLCT state, which results in weak visible light absorption and a short triplet excited state lifetime, respectively. This mini review introduces the recent progress of the development of the transition metal complexes as well as the organic triplet PSs that show a strong visible-light-harvesting ability and long triplet excited state lifetimes. The application of these new triplet PSs in photocatalytic H2 evolution and photoredox catalytic synthetic organic reactions is summarized.

Visible-Light Photoinitiation of (Meth)acrylate Polymerization with Autonomous Post-conversion.

Conversion plateaus rapidly in radical photopolymerizations (RPPs) following discontinuation of irradiation due to rapid termination of reactive radicals, which restricts the wider use of RPPs in applications that involve nonuniform light access including those with attenuated light transmission or irregular surfaces. Based on our recent report of a radical dark-curing photoinitiator (DCPI) that continues polymerization beyond the cessation of irradiation by enabling latent redox initiation with photo-released amine in the presence of a suitable oxidant, we developed a new DCPI with an absorption spectrum that extends well into the visible range. Our design process involved a series of computational investigations of candidate molecules, including a systematic study of substituents and their position-dependent effects on absorption characteristics, electronic transitions, and the photochemical mechanism and its associated energetics. Our quantum chemical computations identified the target compound 5,7-dimethoxy-6-bromo-3-aroylcoumarin-DMPT/BPh4 and predicted that it would facilitate the dark-curing mechanism by concurrent photo-radical generation and photo-induced release of an efficient redox reductant under visible irradiation. This reductant-tethered chromophore was then synthesized and optically characterized with UV-vis spectroscopy that revealed its strong visible-light absorption with a molar absorptivity of 5710 M-1 cm-1 at 405 nm and 50 M-1 cm-1 at 455 nm. We then demonstrated extensive dark-curing of >35% additional conversion over 25 min following brief activation of the shelf-stable one-part system by irradiation with a 455 nm LED that was ceased at 20% conversion. In contrast, shuttering irradiation of the control formulation at that same point resulted in immediate cessation of conversion, which plateaued at 20%. We determined a remarkable initiator efficiency of 2.82 that results from the additional redox-generated radicals with a 77% photo-reductant generation quantum yield. The combination of superior photo- and dark-curing efficiencies of this new visible DCPI is expected to open new application opportunities in RPP, especially those involving resins that are highly light attenuating, surfaces that possess irregular features that produce uneven irradiance, and production lines where continued dark-curing downstream of the light activation step enhances line efficiencies.

Defects regulation of Sb2S3 by construction of Sb2S3/In2S3 direct Z-scheme heterojunction with enhanced photoelectrochemical performance

Antimony sulfide (Sb2S3), as a narrow band-gap semiconductor with strong visible light absorption ability, nevertheless due to the existence of a large number of defective energy levels, the application in the field of PEC water splitting was limited. This paper aimed to construct Sb2S3/In2S3 direct Z-scheme heterojunction to effectively eliminate the adverse effect of defective energy level on the photoelectrochemical performance of Sb2S3. Cell-like Sb2S3 thin films were prepared on ITO substrates by simple hydrothermal method, followed by using solvothermal method, the Sb2S3/In2S3 direct Z-scheme heterojunction was successfully constructed. The IPCE values of Sb2S3/In2S3 could reach 10.19 % (735 nm) compared with pure Sb2S3 (4.22 %). Both the separation and injection efficiency could be improved from 3.35 % and 31.69 % to 5.19 % and 61.48 %, respectively. The maximum photocurrent density was 1.24 mA/cm2 at 1.23 V vs. RHE, which was 5.6 times higher than pristine Sb2S3 (0.22 mA/cm2). Moreover, an earlier onset potential was observed (~0.7 V vs. RHE), showing an improvement of 0.3 V when compared to the pristine Sb2S3. This work provided a new idea for the application of antimony chalcogenides in the field of PEC water splitting and the construction of efficient photoelectric devices.

Ruthenium(II) complexes coordinated to graphitic carbon nitride: Oxygen self-sufficient photosensitizers which produce multiple ROS for photodynamic therapy in hypoxia

The photodynamic therapy (PDT) of cancer is limited by tumor hypoxia as PDT efficiency depends on O2 concentration. A novel oxygen self-sufficient photosensitizer (Ru-g-C3N4) was therefore designed and synthesized via a facile one-pot method in order to overcome tumor hypoxia-induced PDT resistance. The photosensitizer is based on [Ru(bpy)2]2+ coordinated to g-C3N4 nanosheets by Ru–N bonding. Compared to pure g-C3N4, the resulting nanosheets exhibit increased water solubility, stronger visible light absorption, and enhanced biocompatibility. Once Ru-g-C3N4 is taken up by hypoxic tumor cells and exposed to visible light, the nanosheets not only catalyze the decomposition of H2O2 and H2O to generate O2, but also catalyze H2O2 and O2 concurrently to produce multiple ROS (•OH, •O2−, and 1O2). In addition, Ru-g-C3N4 affords luminescence imaging, while continuously generating O2 to alleviate hypoxia greatly improving PDT efficacy. To the best of our knowledge, this oxygen self-sufficient photosensitizer produced via grafting a metal complex onto g-C3N4 is the first of its type to be reported.