Photoreduction Process Research Articles

Removing trace chromium from high concentration vanadium solution by photoreduction deposition with Ti–Zr solid solution

The preparation of ultrahigh-purity vanadium (>99.99 wt%) requires the removal of trace amounts of chromium, but economical vanadium purification is difficult to achieve using crude vanadium mother liquors (>98 wt%) because of the similar properties of V(V) and Cr(IV) ions. In this study, a Ti–Zr solid solution was used for the deep purification of high-concentration ammonium polyvanadate by removing trace chromium using photocatalytic reduction process. The results show that V(V) and Cr(VI) are competitively adsorbed and photoreduced, but V(V) adsorption is preferred and occurs more rapidly than that of Cr(VI). However, after the photoreduction product of V(V), V(IV) is desorbed, whereas after that of Cr(VI), Cr(III) is deposited on the photocatalyst, achieving the separation of vanadium and chromium. The 2 h removal efficiency of chromium exceeds 80%, and the chromium content in the obtained vanadium is less than 0.04 wt%. After precipitation, the chromium content in the obtained ammonium metavanadate is less than 0.001 wt%, and the purity of the final V2O5 product exceeds 99.99%, which meets the requirement for ultrahigh-purity vanadium products. The used photocatalyst can be regenerated and reused with stable performance. This work provides a reference method for ultrahigh-purity vanadium production and an example of the industrial application of the photoreduction process.

Surface disinfection with silver loaded pencil graphite prepared with green UV photoreduction technique

Carbon-based materials have been studied for their antimicrobial properties. Previously, most antimicrobial studies are investigated with suspended nanoparticles in a liquid medium. Most works are often carried out with highly ordered pyrolytic graphite. These materials are expensive and are not viable for mass use on high-touch surfaces. Additionally, highly antimicrobial silver nanoparticles are often incorporated onto substrates by chemical reduction. At times, harmful chemicals are used. In this work, low-cost graphite pencils are mechanically exfoliated and transferred onto Si substrates. The sparsely-covered graphite flakes are treated by either plasma O2 or UV irradiation. Subsequently, Ag is photo reduced in the presence of UV onto selected graphite flake samples. It is found that graphite flake surface topography and defects are dependent on the treatment process. High surface roughness and (defects density, I D/I G) are induced by plasma O2 follows by UV and pristine graphite flake as follows: 6.45 nm (0.62), 4.96 nm (0.5), 3.79 nm (0.47). Antimicrobial tests with E. coli reveal high killing efficiency by photoreduced Ag-on-graphite flake. The reversible effect of Ag leaching can be compensated by repeating the photoreduction process. This work proposes that UV treatment is a promising technique over that of plasma O2 in view that the latter treated surface could repel bacteria resulting in lower bacteria-killing efficiency.

Photochemical synthesis of Au nanostars on PMMA films by ethanol action as flexible SERS substrates for in-situ detection of antibiotics on curved surfaces

• Photochemical fabrication of Au NSs by the action of ethanol has been demonstrated. • Au NSs are employed directly on the flexible PMMA substrate for SERS application. • High enhancement factors about 10 9 are achieved for the antibiotics. • Effective multiplex SERS detection towards CPX and CAP is presented. • In-situ detection of antibiotics in chicken-wing samples was performed. Enormous Raman signal enhancement using gold nanostars (Au NSs) has attracted great attention due to the excitation of strong electric field on the nanostar tips. The synthetic methods of Au NSs mainly utilize specialized shape-directing agents, such as surfactants or polymers, to assist the tip formation. However, these agents passivate nanostar surfaces and weaken the interaction between Au NSs and analyte molecules. Herein, we report the synthesis of Au NSs with clean surface by the action of ethanol through a facile photoreduction process. The growth mechanism of Au NSs is elucidated and discussed with the action of ethanol as a polar protic solvent. The synthesis process of Au NSs is employed directly on poly(methyl methacrylate) (PMMA) films for the application of surface-enhanced Raman spectroscopy (SERS). The proposed flexible Au-NSs/PMMA SERS substrate is characterized by the SERS detection of two antibiotics, ciprofloxacin (CPX) and chloramphenicol (CAP). The superior detection performance includes high sensitivity, high enhancement factor (2.03 × 10 9 ), low limit of detection (3.41 × 10 -11 M), superior multiplex detection ability, good mechanical stability, excellent uniformity and reproducibility (<7.32 %). These superior sensing properties can be attributed to a large number of hotspots formed by diverse nanostructures at different positions of Au NSs on the Au-NSs/PMMA SERS substrate. The multiplex SERS detection ability is also explored for the simultaneous detection of multiple analytes. The transparent and flexible nature of the Au-NSs/PMMA SERS substrate enables the in-situ, real-time detection of CPX and CAP in chicken-wing samples by using the fiber-coupled Raman probe with the low LODs. The reported flexible SERS substrate opens the way to improve the practical detection of various antibiotics for the worldwide food safety issues.

Electron-coupled enhanced interfacial interaction of Ce-MOF/Bi2MoO6 heterostructure for boosted photoreduction CO2

To achieve the task of “Carbon neutrality” in China, the photoreduction of CO2 was applied over the solid-phase synthesized Ce-MOF/Bi2MoO6 heterostructure. The inexhaustible driven force of sunlight was adopted and the value-added chemicals of methane, methanol and formic acid were obtained during photoreduction. The firstly successful construction of Ce-MOF/Bi2MoO6 heterostructure was generated by their intense contact via the electron-coupled structure, which could take full advantage of the high surface area of Ce-MOF and the efficient electrons transfer of Bi2MoO6. The segregation and transport of photoexcited carriers were heightened by the enhanced interfacial interaction. Moreover, the generation of HCOOH appeared only over the composites, which was caused by the inhibition of the fast interaction between the photoexcited electrons and CO2-reduced intermediates. As a result, the CO2 photoreduction performance of electrons-induced heterostructured of Ce-MOF/Bi2MoO6 composites exhibited higher CH4, CH3OH and HCOOH yield amount than the neat Ce-MOF and BMO. The optimized photocatalyst reached up to 113.87 μmol·h−1·g−1 of CH4, 40.59 μmol·h−1·g−1 of CH3OH and 73.48 μmol·h−1·g−1 of HCOOH. The mechanism of CO2 photoreduction process was gained by ESR and in-situ DRIFTS techniques.

Enhanced photocatalytic degradation of tetracycline hydrochloride by Ag/AgI/WO3·H2O composites

AbstractNovel visible light response Z‐scheme Ag/AgI/WO3·H2O composite photocatalysts were synthesized using a two‐step hydrothermal method followed by a photoreduction process without adding any surfactant. The synthesized Ag/AgI/WO3·H2O composite (AAW‐2) with the Ag/WO3·H2O molar ratio of 0.8/1 showed the highest photodegradation activity for tetracycline hydrochloride (TCH) solution under visible light, and its rate constant was 24.6 times higher than that of WO3·H2O. The enhanced photocatalytic activity of the Ag/AgI/WO3·H2O composite can be due to the efficient separation of the electron–hole pairs through the Z‐scheme Ag/AgI/WO3·H2O structure. The AAW‐2 composite exhibited excellent stability toward TCH degradation after four successive circulations. Finally, the photocatalytic mechanism of the Ag/AgI/WO3·H2O composite was proposed based on the radical‐trapping experiments, where h+ and •O2− were the main active species during the photocatalytic reaction.

Investigation of CO2 Photoreduction in an Annular Fluidized Bed Photoreactor by MP-PIC Simulation.

Carbon dioxide (CO2) photoreduction is a promising process for both mitigating CO2 emissions and providing chemicals and fuels. A gas–solid two-phase annular fluidized bed photoreactor (FBPR) would be preferred for this process due to its high mass-transfer rate and easy operation. However, CO2 photoreduction using the FBPR has not been widely researched to date. The Lagrangian multiphase particle-in-cell (MP-PIC) simulation with computational fluid dynamic models is a new and robust approach to explore the multiphase reaction system in the gas–solid fluidized bed. Therefore, the purpose of this paper is to investigate CO2 photoreduction in the FBPR by MP-PIC modeling to understand the intrinsic mechanism of solid flow, species mass transfer, and CO2 photoreaction. The MP-PIC models for solid flow in the FBPR were validated by the bed expansion height and bubble size. The results showed the particle stress of the Lun model, the drag of the Ergun-WenYu (Gidaspow) model, and the coefficient of restitution e = 0.95 with the wall parameters ew = 0.9 and μw = 0.6 are the best fit to the experimental empirical correlations. The MP-PIC models developed in this work proved to be better than the Eulerian two-fluid modeling in the prediction of the bed expansion height and bubble size. It was also found from the simulation results that the maximum radiation intensity is in the half reactor height area, and the photocatalytic reaction mainly occurred around the inner wall. It showed that the gas velocity and catalyst loading were two crucial operating parameters to control the process. The results reported here can provide guidance for the operation and reactor design of the CO2 photoreduction process.

Anisotropic growth of gold nanocrystals induced by concerted adsorption using a photochemical approach

Photochemical reduction of noble metal ions in the presence of stabilizers that selectively adsorb on different crystal planes is a fascinating method for synthesizing shape-controlled metal nanocrystals (NCs). In this study, we demonstrate the photoreduction of Au3+ ions in the presence of polyvinylpyrrolidone (PVP) and Br− ions, that are classified into different categories of protective agents. Au nanoplates with atomically flat surfaces are obtained by the photoirradiation of an aqueous solution containing Au3+, PVP and Br−. Notably, PVP preferentially adsorbs along the perimeter, while Br− ions tend to adsorb on the flat top and bottom (111) faces. The selective adsorption of these structurally distinct stabilizers promotes two-dimensional growth of the Au nanoplates. PVP serves not only as a protective agent but also as a reduction agent in the photoreduction process. At high concentrations of Br− ions, the adsorption of the Br− ions also occurs at the perimeter, which kinetically traps the side growth of the nanoplates and leads to the formation of polygonal Au nanoplates. In other words, competitive adsorption of PVP and Br− at the facets and their density kinetically affect the shape of the formed Au NCs. This concept was successfully applied to control the photoreduction of Au3+ ions into icosahedral Au nanoparticles.

Effect of laser fluence and charge compensation defects on photoreduction of Eu ions in KSrPO4 crystal using a UV laser

In our previous study, Eu ions in KSrPO4 were reduced from trivalent to divalent by irradiation with a Nd:YVO4 nanosecond laser at a wavelength of 266 nm. This reduction was caused by laser light, so this phenomenon was termed photoreduction. Here, the effect of the laser fluence and charge compensation defects on photoreduction were investigated to model the process. The dependence of the amount of Eu ions reduced on the photoluminescence intensity suggests that a two-photon process is involved. Considering the energy of the laser wavelength at which photoreduction occurs, the two photons were attributed to the excitation of [Eu3+-O2-] charge transfer and charge transfer from a Sr vacancy to the conduction band, respectively. KSrPO4:Eu phosphors co-doped with various metal ions were synthesized, and photoreduction was conducted on these phosphors. In the case of co-doping trivalent metal ions, the amount of reduced Eu ions was increased, while the amount was decreased when co-doping monovalent ions. We consider that this difference is due to the change in the defect state of KSrPO4:Eu by co-doping metal ions and suggest that the presence of charge compensation defects, such as Sr vacancies, are important in the photoreduction process. Based on these results, we model the photoreduction process and discuss the details of the mechanism.

Role of Cu0-TiO2 interaction in catalyst stability in CO2 photoreduction process

The application of copper-based semiconductors for CO2 photoreduction has been limited by the poor stability of these catalysts in aqueous solutions due to parallel oxidation reactions. Thus, here we discussed the role of the Cu0-TiO2 interaction in catalyst stability, where the semiconductor acts as a charge separator and support for Cu0. Cu0 nanoparticles were deposited on the surface of TiO2 by reducing copper nitrate using a sodium borohydride solution. The metallic copper presents a higher selectivity in CO production (82.32%), while pure TiO2 presents a selectivity for CH4 (62.44%). However, with the heterostructure formation, the photocatalysts activity increases and the selectivity changes with copper amount variation over TiO2. In addition to the obtained C1 products (CH4, CO, and CH3OH), products containing two or more carbons (C2+) were also generated, such as acetic acid (C2H4O2), acetone (C3H6O), and isopropanol (C3H8O). H2 was also produced, although the selectivity for products derived from the photoreduction of CO2 was significantly greater. The sample TiO2/Cu 30% was significantly stable, which indicated the importance of an adequate heterojunction in the catalyst activity. These results demonstrate the synergistic effect between different copper species over TiO2, in which both materials play a role in the catalytic event.

Synthesis of CdS nanomaterials and their photocatalytic activity under visible light

CdS nanomaterial was hydrothermally synthesized at 160 oC for 6 hours from a dispersed mixture of Cd(NO3)2.4H2O and CH3CSNH2 in 50 mL ethylenediamine and denoted as Cw-m, where w-m is the weight ratio of Cd(NO3)2.4H2O/CH3CSNH2 and equals to 1-2, 1-1 and 3-2. The obtained materials were characterized by X-Ray Diffraction (XRD), Infrared spectra (IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-Vis-DRS). The UV-vis DRS showed that the CdS materials possess bandgap of around 2.24 eV. The photocatalytic activity of the CdS was assessed by degradation of methylene blue (MB) under visible light. The experiments indicated that CdS semiconductor materials can be active under visible light. The MB degradation over the CdS was mainly attributed to the photoreduction process induced by the superoxide radical anions (O2• -) and hydroxyl radicals (•OH).

Bionic Optical Leaf for Photoreduction of CO2 from Noble Metal Atom Mediated Graphene Nanobubble Arrays.

The reduction of CO2 to useful chemicals by solar irradiation has been of great interest in recent years to tackle the greenhouse effect. Compared with inorganic metal oxide particles, carbonaceous materials, such as graphene, are excellent in light absorption; however, they lack in activity and selectivity because of the challenge to manipulate the band gap and optimize the electron-hole separation, which drives the photoreduction process. In this work, inspired by the delicate natural plant leaf structure, we fabricated orderly stacked graphene nanobubble arrays with nitrogen dopant for the coordination of noble metal atoms to mimic the natural photoreduction process in plant leaves. This graphene metamaterial not only mimics the optical structure of leaf cells, which scatter and absorb light efficiently, but also drives the CO2 reduction via nitrogen coordinated metal atoms as the chlorophyll does in plants. Our characterizations show that the band gap of nitrogen-doped graphene could be precisely tailored via substitution with different noble metal atoms on the doped site. The noble atoms coordinated on the doped site of graphene metamaterial not only enlarge the light absorption volume but also maximize the utilization of noble metals. The bionic optical leaf metamaterial coordinated with Au atoms exhibits high CO productivity up to 11.14 mmol gcat-1 h-1 and selectivity to 95%, standing as one of the best catalysts among the carbonaceous and metal-based catalysts reported to date. This catalyst also maintained a high performance at low temperatures, manifesting potential applications of this bionic catalyst at polar regions to reduce greenhouse gases.

Nanostructured heterogeneous photocatalyst materials for green synthesis of valuable chemicals

The photocatalytic process employing nanostructured semiconductor materials has attracted great attention in energy production, CO2 reduction, and water/air purification for decades. Recently, applying heterogeneous photocatalyst for the synthesis of valuable chemicals is gradually emerging and considered as a promising process for the conversion of cheap resources (i.e., biomass derivatives, polyols, and aromatic hydrocarbons). Compared with traditional thermal catalytic approaches, the photocatalytic process provides a mild reaction condition and flexible platform (photocatalyst) that allows precise tweaking of reaction intermediates and reaction pathways, thus resulting in fine control of the selective synthesis of specialized chemicals that are challenging for thermal catalysis. In this review, we summarize recent achievements in photocatalytic synthesis of various industrial important chemicals via photo-oxidative and photo-reductive processes. The selective oxidation of alcohols and aromatics, epoxidation of alkenes, hydrogenation of gaseous molecules and hydrocarbons, and coupling reactions by means of various photocatalysts including metal oxides, supported plasmonic metal nanostructures, conjugated organic polymers, anchored homogeneous catalysts, and dye-sensitized heterostructures are discussed from a material perspective. In addition, fundamental understandings of reaction mechanisms and rational design of nanostructured photocatalysts for enhancing efficiency, selectivity, and stability are discussed in detail.

Role of the Polymeric Matrix and Surface Affinity During Gold Nanoparticles Patterning by Multi-Photon Photo-Reduction

Gold nanoparticles (GNPs) can be patterned on specific positions and substrates by Multi-Photon Direct Laser Writing (MP-DLW) in wet polymeric matrices doped with tetrachloroauric acid (HAuCl₄) as gold precursor. The Hamaker constants describing the GNP-GNP interaction and the interaction between the GNPs and the surrounding materials is described, defining the role of the polymeric matrix; thus, its limits and the advantages are thoroughly analysed. The Multi-Photon Photo-Reduction (MPPR) process, leading to the GNPs creation, triggers a local temperature rising, which can ablate the polymer and influences the particle distribution, size and density. The GNPs polydispersity also depends on the water content in the film, variable because of the vaporization. A protocol to perform MP-DLW of GNPs, without the use of the polymer is illustrated: by treating the surface with a surfactant, it is possible to make the particles stick to the substrate, control their size and reduce the diffusive and convective effects generated by the MPPR.

Excellent photoreduction performance of U(VI) on metal organic framework/covalent organic framework heterojunction by solar-driven

The conversion of uranium(U) from soluble U(VI) into insoluble U(IV) by photocatalytic reduction is an implementable removal technology. In this investigation, two common MOFs photocatalysts (MOF-In, MOF-Ti) and the assembled MOF@COF (2D Schiff base, NH2-MIL-125(Ti)@TpPa-1) were applied for photocatalytic reduction of U(VI). These as-synthesized photocatalysts were characterized by XRD,SEM, TEM, XPS, DRS, EIS, photocurrent and Mott-Schottky plots. The results shown that the constructed NH2-MIL-125(Ti)@TpPa-1 heterojunction not only broadened the scope of visible light response to orange light (600 nm), but also expedited the separation of photogenerated carriers and facilitatedthe U(VI)photoreduction. Specially, the photoreduction removal rates of U(VI) were NH2-MIL-68(In) (55.6%), NH2-MIL-125(Ti) (57.7%), NH2-MIL-125(Ti)@TpPa-1 (81.6%), and the heterojunction of NH2-MIL-125(Ti)@TpPa-1 was about 1.5-fold higher than that of NH2-MIL-125(Ti). Meanwhile, during the photoreduction process, photogenerated electrons and superoxide radicalsplayed the dominant roles in converting U(VI) into U(IV). Moreover, the presence of active Ti3+and oxygen vacancycould effectively promotesuperoxide radicalgeneration and inhibit recombination of photogenerated carriers. Combined with the U(VI) adsorption by NH2-MIL-125(Ti)@TpPa-1 in previously studied, altogether, MOF@COF hybridization can play a synergistic role of adsorption-photocatalytic reduction in the practical application of U(VI) elimination. Therefore, it can be predicted that 2D COF-based hybridization materials have a brilliant application prospect in pollutant purification by solar energy.

Reaction Mechanism of the Enhanced Reaction Activity and Rate of N-Doped CoO Photocatalysts for Photoreduction of CO2 in Air

The use of light to directly reduce CO2 in the atmosphere is the actual development trend of photocatalysis applications in the future. However, it is still in the initial stage of exploration. In this work, oleylamine is used as a template in a one-step hydrothermal method to obtain the N-doped CoO catalyst that can be used to efficiently reduce CO2 in air. N-doped CoO achieves ultrahigh CO2 conversion efficiency (about 75%), amazing CO yield (2.902 mmol g–1 h–1), and superior CO conversion frequency (TOFCO > 300) in air. However, in a 0.03% simulated atmosphere (Ar/CO2), the CO precipitation rate drops by 18 times, while the H2 precipitation rate increases significantly. Quasi-in situ spectroscopy and experimental studies show that O2 in the CO2 reduction process will promote the formation of an amorphous layer with a small number of hydroxyl groups on the surface of N-doped CoO. This amorphous/crystalline interface will effectively promote the catalytic reduction of CO2. This work has inspired further research on the photoreduction process of low-concentration CO2 in the future.

Efficient visible light initiated one-pot syntheses of secondary amines from nitro aromatics and benzyl alcohols over Pd@NH2-UiO-66(Zr)

Pd@NH2-UiO-66(Zr), with small-sized Pd nanoparticles encapsulated inside the cavities of NH2-UiO-66(Zr), was obtained via a double-solvent impregnation followed by a photoreduction process, which shows superior activity for the visible light initiated syntheses of secondary amines from nitro compounds and alcohols, via a sequential photocatalytic hydrogenation of nitro compounds/dehydrogenation of alcohols, condensation of amines and aldehydes to imines, and the hydrogenation of imines. Simultaneous consumption of photogenerated electrons/holes in the photocatalytic hydrogenation of nitro compounds to amines and dehydrogenation of alcohols to aldehydes promotes the whole reaction. Due to the confinement effect of the cavity and the small-sized Pd nanoparticles, Pd@NH2-UiO-66(Zr) shows significantly superior performance as compared with Pd/NH2-UiO-66(Zr), in which larger Pd nanoparticles are deposited on the surface. This study provides an efficient and green strategy for the production of secondary amines and highlights the great potential of using M/MOFs nanocomposites as multifunctional catalysts for light induced one-pot tandem reactions.

Mesoporous tellurium oxide incorporated g-C3N4 for boosted photoinduced – visible-light reduction of Hg(II)

Two-dimensional (2D) tellurium oxide (TeO2) nanoparticles were homogenously incorporated porous graphitic carbon nitride (g-C3N4) utilizing a simple synthesis sol–gel approach in the occurrence of soft and hard templates. The photocatalytic performance of TeO2/g-C3N4 photocatalysts was performed to reduce Hg(II) ions during visible light illumination. α-TeO2 NPs as tetragonal phases are uniformly scattered with small particle size (15 nm) onto layer structure of g-C3N4. The highest photocatalytic performance (100%) within 40 min is 3 %TeO2/g-C3N4 photocatalyst, and it was enhanced 6.66 and 3.7 folds larger than bare g-C3N4 and TeO2. The rate constant of 3 %TeO2/g-C3N4 photocatalyst is fostered nearly 7.6 and 14.3 times larger than the bare TeO2 NPs and g-C3N4. TeO2 with a nanoscale diameter size (∼15 nm) exhibited a higher photoreduction rate and faster kinetics. Such high reduction ability over TeO2/g-C3N4 photocatalyst was ascribed to the advantageous construction of TeO2/g-C3N4 heterojunction, the synergistic effects of TeO2 and g-C3N4 and the enhancement in electron mobility and efficient electrons and holes separation rate. Owing to such advantageous properties, the 2D- TeO2/g-C3N4 photocatalyst presents promising application potentials as a high-performance photoreduction process.

Crafting of plasmonic Au nanoparticles coupled ultrathin BiOBr nanosheets heterostructure: steering charge transfer for efficient CO2 photoreduction

Integrating semiconductor photocatalysts with outstanding visible light absorption and fast surface/interface charge transfer kinetics is still an enormous challenge for efficient CO2 photoreduction. In this work, the Au nanoparticles have been coupled with ultrathin BiOBr nanosheets, the formed heterostructure (Au/BiOBr) possesses a localized surface plasmon resonance (LSPR) and enhances the visible light absorption ability, as well as forms a fast charge transport channel on the interface between Au and BiOBr. Thus, the heterostructure photocatalyst exhibits higher photocatalytic CO2 to CO performance (135.3/16.43 μmol g−1) than that of BiOBr (89.0/6.46 μmol g−1) under 300 W Xe lamp and visible light (λ > 400 nm) irradiation for 5 h, respectively. Finally, the in situ FT-IR spectroscopy revealed CO2 photoreduction process and found that the ∗COOH is the key intermediate for CO2 to CO. This work provides an effective method to construct multielectron transfer scheme for efficient photocatalytic CO2 reduction.

Lanthanide Luminescence Supramolecular Switch Based on Photoreactive Ammonium Molybdate.

Lanthanide supramolecular assemblies as photoswitches have attracted much attention in the fields of cellular imaging and light-emitting materials. However, the regulation of lanthanide luminescence behavior by redox of metal ions is rare. Herein, we constructed a lanthanide luminescence supramolecular switch, that is, a binary assembly constructed by mono-(6-ethylenediamine-6-deoxy)-β-cyclodextrin (ECD) and ammonium molybdate tetrahydrate ((NH4)6Mo7O24·4H2O, Mo7), and further assembled into ternary assemblies with polyoxometalate Na9[XW10O36]·32H2O (X-POM, X = Eu and Dy), which was comprehensively characterized by UV-vis, fluorescence, NMR, Fourier transform infrared, dynamic light scattering, scanning electron microscopy, and ζ potential. Thanks to the oxygen-shielding effect of secondary supramolecular assembly, the photoreduction process of Mo7 (VI) could occur rapidly and efficiently. Due to the high Förster resonance energy transfer (FRET) efficiency of X-POM and Mo7 (V) in supramolecular assembly, the photoreduction process is accompanied by fluorescence quenching. In addition, the oxidation process of the Mo7 (V) could be rapidly promoted by heating, which allowed the X-POM fluorescence to recover. Interestingly, ECD-mediated ternary supramolecular assemblies not only tune the lanthanide luminescence but also strongly increase the lanthanide luminescence behavior, leading to the emission of strong narrow red light at 5D0-7F4, which can be successfully applied to two-dimensional code anticounterfeiting. In this study, a new approach is provided for the construction of lanthanide luminescence supramolecular switches tuned by photoreactive polyoxometalate.

Leaf-Vein structure like g-C3N4/P-MWNTs donor-accepter hybrid catalyst for efficient CO2 photoreduction

Separation efficiency of photogenerated carriers and CO2 adsorption ability of the catalyst are two important factors affecting the photoreduction performance of CO2. In view of the above analyses, leaf-vein like 2D-1D g-C3N4/P-MWNTs donor/acceptor semiconductor-carbon hybrid composite has been successfully prepared by the simple co-grinding/calcination processes. UV–vis DRS results showed that the modification of P-MWNTs can enhance the photo-absorption ability of the composite. Photoelectrochemical tests proved that 2D-1D Schottky-like barriers can enlarge the separation and transfer efficiency of photogenerated carriers. BET and CO2-adsorption tests exhibited that the introduction of P-MWNTs can greatly increase the CO2 capture ability of the composite. CO2 photoreduction experiments confirmed that the composite had much more excellent CO2 photoreduction performance than the pure g-C3N4 under the irradiation of UV–vis light or visible light. In-situ FTIR and 13C isotope tracer tests were applied to research the CO2 photoreduction processes. Finally, the synergistic effect on CO2 photoreduction process between electron transfer and CO2 adsorption behavior has been discussed in total.