Visible Light Energy Research Articles

Luminescent down-shifting aluminosilicate nanocomposites: an efficient UVA shielding material for photovoltaics

In this investigation polycarbonate (PC) nanocomposites (NC) films have been fabricated with varying amounts of alluminosilicate nanotubes (HNT) using solvent intercalation method. On the basis of UV–Vis experiments, the effect of HNT on absorption coefficient spectra of PC/HNT NC films is demonstrated. A distinct reduction of band gap energy is being a result of HNT doping which leads to the formation of charge transfer complexes (CTC) and π-conjugation between HNT and PC matrix. Further absorption bands and absorption edge parameters such as Urbach energy (Eu) and energy gap (Eg) are used to evaluate the changes in the NC films. The structural and morphological aspects of PC/HNT NC were evaluated by Fourier transform infrared spectroscopy, X-Ray diffraction studies and scanning electron microscopy. Absorbance and transmittance spectra of luminescent PC/HNT NC films reveals the conversion of higher energy UVA light in to lower energy visible light which leads to efficient photovoltaic application.

Hybrid Au-Ag Nanostructures for Enhanced Plasmon-Driven Catalytic Selective Hydrogenation through Visible Light Irradiation and Surface-Enhanced Raman Scattering.

Herein, we report the successful application of hybrid Au-Ag nanoparticles (NPs) and nanochains (NCs) in the harvesting of visible light energy for selective hydrogenation reactions. For individual Au@Ag NPs with Au25 cores, the conversion and turnover frequency (TOF) are approximately 8 and 10 times higher than those of Au25 NPs, respectively. Notably, after the self-assembly of the Au@Ag NPs, the conversion and TOF of 1D NCs were approximately 2.5 and 2 times higher than those of isolated Au@Ag NPs, respectively, owing to the coupling of surface plasmon and the increase in the rate at which hot (energetic) electrons are generated with the formation of plasmonic hot spots between NPs. Furthermore, the surface-enhanced Raman scattering (SERS) activity of 1D Au@Ag NCs was strengthened by nearly 2 orders of magnitude.

Effect of metal doping on the visible light absorption, electronic structure and mechanical properties of non-toxic metal halide CsGeCl3.

Non-toxic metal halide perovskites have become forefront for commercialization of the perovskite solar cells and optoelectronic devices. In the present study, for the first time we show that particular metal doping in CsGeCl3 halide can considerably enhance the absorbance both in the visible and ultraviolet light energy range. We have carried out DFT based first principles calculations on Mn-doped and Ni-doped CsGeCl3 halide. We investigate the detailed structural, optical, electronic and mechanical properties of all the doped compositions theoretically. The study of the optical properties shows that the absorption edge of both Ni and Mn-doped CsGeCl3 is shifted toward the low energy region (red shift) relative to the pristine one. An additional peak is observed for both doped profiles in the visible light energy region. The study of the mechanical properties demonstrates that both the doped samples are mechanically stable and ductile as the pristine CsGeCl3. The study of the electronic properties shows that the excitation of photoelectrons is easier due to the formation of intermediate states in Mn-doped CsGeCl3. As a result Mn-doped CsGeCl3 exhibits higher absorptivity in the visible region than the Ni-doped counterpart. A combinational analysis indicates that CsGe1−xMnxCl3 is the best lead free candidate among the inorganic perovskite materials for solar cell and optoelectronic applications.

Dielectric Properties of Photo-Luminescent CdSe/CdS Mono-Shell and CdSe/CdS/ZnS Multi-Shell Nanocrystals Studied by TEM-EELS

Semiconductor nanocrystals (NCs) of CdSe/CdS (core/shell) mono-shell and CdSe/CdS/ZnS (core/shell/shell) multi-shell having bright and stable luminescence were investigated using high energy-resolution electron energy-loss spectroscopy (EELS) based on transmission electron microscopy to evaluate their dielectric properties in the visible light energy region. EELS spectra of the mono-shell and multi-shell NCs showed two-step structures attributed to interband transitions near band gaps of individual CdSe core and CdS shell. EELS simulations based on the classical dielectric theory revealed that the two-step structures were results of dielectric response from CdSe core and CdS shell. The intensity profiles of the two-step structures depend on a thickness of CdS shells and mono/multi-shell structures of NCs. Besides, the quantum confinement effect was observed in the spectra of mono- and multi-shell NCs, where onset energy of the CdSe core was larger than that of bulk CdSe. The EELS spectra of multi-shell NCs, however, did not present an evident onset due to a bandgap of ZnS outer-shell suggesting defects or amorphous state in ZnS outer-shell. Such dielectric properties of NCs obtained from EELS analysis could provide valuable information to evaluate the crystallinity of individual core and shells in NCs.

Visible-light induced copper(i)-catalysed denitrogenative oxidative coupling of hydrazinylpyridines with terminal alkynes

An effective and green approach to oxidative Csp2–Csp coupling of 2-hydrazinylpyridine with terminal alkynes to form 2-(alkyl/arylethynyl) pyridine via N2 elimination through the cleavage of a non-activated C–N bond under low energy visible light at room temperature (42 examples).

Photoactivation of imatinib–antibody conjugate using low-energy visible light from Ru(ii)-polypyridyl cages

Ru(ii)-polypyridyl cages with sterically bulky bidentate ligands provide efficient photochemical release of the anticancer drug imatinib using low energy visible light, imparting spatiotemporal control over drug bioavailability. The light-activated drug release is maintained when the Ru(ii) cage is covalently coupled to an antibody, which is expected to localize selectively on the tumor.

Largely enhanced near band edge emission of ultrathin zinc oxide nanowire/gold nanoparticles composites by surface plasmon resonance

Ultrathin zinc oxide nanowires with diameter less than 50nm were synthesized by polyethyleneimine assisted solution method. Zinc oxide nanowire near band edge emission was enhanced obviously by gold nanoparticles coating, and a max 26 times enhancement was realized. The defects caused visible light emission was also quenched to noise level when gold was deposited more than 10s. The large near band edge emission enhancement was caused by surface plasmon resonance mediated luminescent energy transfer, which absorbed the visible light energy and transferred to the near band edge emission. The large surface to volume ratio enhanced the coupling strength between gold nanoparticles and ultrathin zinc oxide nanowires. This research provide a method to improve the luminescent efficiency of zinc oxide nanowires.

The improvement of formic acid production from CO2 with visible-light energy and formate dehydrogenase by the function of the viologen derivative with carbamoylmethyl group as an electron carrier

Formate dehydrogenase (FDH) is an attractive biocatalyst for converting CO2 to formic acid in ambient conditions. FDH is applied to the catalyst for the visible-light induced CO2 – formic acid conversion system consisting of an electron donor, a photosensitizaer and an electron carrier. For improvement of the formic acid production efficiency with this system, the enhancement of electron relay processes among a photosensitizer, an electron carrier and FDH has been needed. We aimed to solve this problem by developing novel electron carrier based on the viologen derivative instead of methylviologen (MV), widely used as an electron carreir. In this study, viologen derivatives with carbamoyl group, 1,1′-dicarbamoylmethyl-4,4′-bipyridinium diiodide (CV) and 1-carbamoylmethyl-1′-methyl-4,4′-bipyridinium diiodide (CMV) were synthesized and applied to the electron carrier for photoinduced CO2-formic acid conversion system consisting of triethanolamine, water-soluble zinc porphyrin and FDH. By using CV and CMV, the effective formic acid production in the system of water-soluble zinc porphyrin and FDH was improved compared with that of MV.

DFT study of benzyl alcohol/TiO2 interfacial surface complex: reaction pathway and mechanism of visible light absorption.

We propose a new pathway for the adsorption of benzyl alcohol on the surface of TiO2 and the formation of interfacial surface complex (ISC). The reaction free energies and reaction kinetics were thoroughly investigated by density functional calculations. The TiO2 surfaces were modeled by clusters consisting of 4 Ti atoms and 18 O atoms passivated by H, OH group and H2O molecules. Compared with solid-state calculations utilizing the periodicity of the materials, such cluster modeling allows inclusion of the high-order correlation effects that seem to be essential for the adsorption of organic molecules onto solid surfaces. The effects of both acidity and solvation are included in our calculations, which demonstrate that the new pathway is competitive with a previous pathway. The electronic structure calculations based on the relaxed ISC structures reveal that the chemisorption of benzyl alcohol on the TiO2 surface greatly alters the nature of the frontier molecular orbitals. The resulted reduced energy gap in ISC matches the energy of visible light, showing how the adsorption of benzyl alcohol sensitizes the TiO2 surface. Graphical Abstract The chemisorption of benzyl alcohol on TiO2 surface greatly alters the nature of the frontier molecular orbitals and the formed interfacial surface complex can be sensitized by visible light.

Platinum electrocatalysts with plasmonic nano-cores for photo-enhanced oxygen-reduction

Platinum (Pt) has been recognized as the most efficient catalyst for the oxygen reduction reaction (ORR). So far, great efforts have been devoted to enhance the ORR activity of Pt by alloying or surface engineering, however, little effect has been devoted to utilizing solar energy to boost the ORR catalysis. Herein a photo-enhanced strategy is developed to improve the ORR activity of Pt with plasmonic nano-cores. Au-Pd-Pt NRs with strong surface plasmon resonance (SPR) absorption are synthesized and Pd serves as the buffer layer. Upon visible-light irradiation, the mass and specific activities over Au-Pd-Pt NRs/C could reach 2.56Amg−1Pt and 3.57mAcm−2 at 0.9V versus RHE, which is 25.6 and 27.5 times higher than those of commercial Pt/C; notably, 2.2-fold enhancement is obtained only with the visible-light energy. These studies may open new avenues to further improve the ORR activity with light energy as a driving force.

Organic degradation potential of a TiO2/H2O2/UV–vis system for dental applications

ObjectivesThe combination of TiO2 and H2O2 under light activation constitutes a promising method for disinfection of dental prosthetics and implants, due to production of reactive oxygen species (ROS). The aim of this work was to investigate the organic degradation ability of TiO2 particles in combination with H2O2 and under light activation utilizing the organic dye rhodamine B (RhB). MethodsFive different types of TiO2 particles, consisting of anatase, rutile, or a mixture of these crystalline phases, were combined with H2O2 and RhB, and subsequently exposed to UV (365nm) or visible (405nm) light at an irradiance of 2.1mW/cm2. ResultsIt was found that rutile in combination with low concentrations of H2O2 (1.0–3.5mM) resulted in a degradation of RhB of 96% and 77% after 10min exposure to 365nm and 405nm light, respectively, which was the highest degradation of all test groups. Control measurements performed without light irradiation or irradiation at 470nm, or without TiO2 particles resulted in little or no degradation of RhB. ConclusionsLow H2O2 concentrations (1.0mM–3.5mM) and visible light (405nm) used in combination with rutile TiO2 particles showed the highest RhB degradation capacity. Clinical significanceA combination of TiO2 particles and H2O2 exposed to low energy UV or high energy visible light has an organic degradation capability that could be utilized in applications to kill or inactivate bacteria on medical devices such as dental implants for treatment against, e.g., peri-implantitis.

4′‐Chlorochalcone‐Assisted Electroactive Polyvinylidene Fluoride Film‐Based Energy‐Storage System Capable of Self‐Charging Under Light

AbstractA simple photovoltaically self‐charging energy‐storage system (PSESS) has been fabricated as an effective solar energy‐storage power cell. The PSESS is capable of the in situ storage of visible light energy in the form of electrical energy. The PSESS is assembled on a photoelectrode (fluorine‐doped tin oxide) that contained a dye‐sensitized and hole‐trapping phenosafranine–polyvinylpyrrolidone film in association with an electroactive and highly dielectric chlorochalcone–polyvinylidene fluoride (PVDF) film, in which photogenerated electrons are stored. Here, chlorochalcone particles act as a catalytic agent for electroactive β crystal nucleation, visible‐light emission, and the improved dielectric value of the composite thin films. A proportion of 85 % electroactive β phase nucleation and a high dielectric constant (≈60) are achieved by incorporating 20 mass % chlorochalcone in PVDF. The self‐charging capability of the PSESS was verified under a light illumination intensity of 110 mW cm−2. The PSESS was charged up to 0.95 V under light illumination. Moreover, the device wass discharged with a constant current density 1.25 mA g−1 for a long time (≈560 min) after the light was switched off. The photogenerated energy and charge density of the PSESS are approximately 5.25 mWh g−1 and 42 C g−1, respectively. The maximum capacitance attained under the light illumination is approximately 44 F g−1, which is many times greater than two‐electrode self‐charged photovoltaic cells reported previously. A blue light‐emitting diode can be driven by using the PSESSs as a power bank.

Single-layer group IV-V and group V-IV-III-VI semiconductors: Structural stability, electronic structures, optical properties, and photocatalysis

Recently, single-layer group III monochalcogenides have attracted both theoretical and experimental interest at their potential applications in photonic devices, electronic devices, and solar energy conversion. Excited by this, we theoretically design two kinds of highly stable single-layer group IV-V ($\mathrm{IV}=\mathrm{Si},\mathrm{Ge}$, and Sn; $\mathrm{V}=\mathrm{N}$ and P) and group V-IV-III-VI ($\mathrm{IV}=\mathrm{Si},\mathrm{Ge}$, and Sn; $\mathrm{V}=\mathrm{N}$ and P; $\mathrm{III}=\mathrm{Al},\mathrm{Ga}$, and In; $\mathrm{VI}=\mathrm{O}$ and S) compounds with the same structures with single-layer group III monochalcogenides via first-principles simulations. By using accurate hybrid functional and quasiparticle methods, we show the single-layer group IV-V and group V-IV-III-VI are indirect bandgap semiconductors with their bandgaps and band edge positions conforming to the criteria of photocatalysts for water splitting. By applying a biaxial strain on single-layer group IV-V, single-layer group IV nitrides show a potential on mechanical sensors due to their bandgaps showing an almost linear response for strain. Furthermore, our calculations show that both single-layer group IV-V and group V-IV-III-VI have absorption from the visible light region to far-ultraviolet region, especially for single-layer SiN-AlO and SnN-InO, which have strong absorption in the visible light region, resulting in excellent potential for solar energy conversion and visible light photocatalytic water splitting. Our research provides valuable insight for finding more potential functional two-dimensional semiconductors applied in optoelectronics, solar energy conversion, and photocatalytic water splitting.

Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications

During the past decade, visible light photocatalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing visible light energy for synthetic purposes through the generation of reactive but controllable free radical species. Recent progress in the area of visible light photocatalysis has established it as an enabling catalytic strategy for the mild and selective generation of nitrogen-centered radicals. The application of visible light for photocatalytic activation of amides, hydrazones, and imides represents a valuable approach for facilitating the formation of nitrogen-centered radicals. Within the span of only a couple of years, significant progress has been made for expediting the generation of amidyl, hydrazonyl, and imidyl radicals from a variety of precursors. This Perspective highlights the recent advances in visible light-mediated generation of these radicals. A particular emphasis is p...

Design and deposition of a metal-like and admittance-matching metamaterial as an ultra-thin perfect absorber

A stratiform metamaterial, comprising metal and dielectric thin films, exhibits both near-perfect antireflection and strong light extinction to function as a perfect and ultra-thin light absorber. The equivalent admittance and extinction coefficient of the metamaterial are tailored using a visual method that is based on an admittance diagram. A five-layered metamaterial was designed and deposited with a total thickness of 260 nm on a mirror to exhibit strong and wide angle absorption over wavelengths from 400 nm to 2000 nm. A seven-layered metamaterial with a total thickness of less than 200 nm was designed and deposited to have equivalent admittance around unity and an extinction coefficient that is comparable to that of metal. Such a metal-like metamaterial exhibits low reflectivity so couples most visible light energy into the films and dissipates energy with an equivalent skin depth of less than 55 nm over visible wavelengths.

One-Pot Large-Scale Synthesis of Carbon Quantum Dots: Efficient Cathode Interlayers for Polymer Solar Cells

Cathode interlayers (CILs) with low-cost, low-toxicity, and excellent cathode modification ability are necessary for the large-scale industrialization of polymer solar cells (PSCs). In this contribution, we demonstrated one-pot synthesized carbon quantum dots (C-dots) with high production to serve as efficient CIL for inverted PSCs. The C-dots were synthesized by a facile, economical microwave pyrolysis in a household microwave oven within 7 min. Ultraviolet photoelectron spectroscopy (UPS) studies showed that the C-dots possessed the ability to form a dipole at the interface, resulting in the decrease of the work function (WF) of cathode. External quantum efficiency (EQE) measurements and 2D excitation-emission topographical maps revealed that the C-dots down-shifted the high energy near-ultraviolet light to low energy visible light to generate more photocurrent. Remarkably improvement of power conversion efficiency (PCE) was attained by incorporation of C-dots as CIL. The PCE was boosted up from 4.14% to 8.13% with C-dots as CIL, which is one of the best efficiency for i-PSCs used carbon based materials as interlayers. These results demonstrated that C-dots can be a potential candidate for future low cost and large area PSCs producing.

Determination of Conduction and Valence Band Electronic Structure of LaTiOx Ny Thin Film.

The nitrogen substitution into the oxygen sites of several oxide materials leads to a reduction of the band gap to the visible-light energy range, which makes these oxynitride semiconductors potential photocatalysts for efficient solar water splitting. Oxynitrides typically show a different crystal structure compared to the pristine oxide material. As the band gap is correlated to both the chemical composition and the crystal structure, it is not trivial to distinguish which modifications of the electronic structure induced by the nitrogen substitution are related to compositional and/or structural effects. Here, X-ray emission and absorption spectroscopy are used to investigate the electronic structures of orthorhombic perovskite LaTiOx Ny thin films in comparison with films of the pristine oxide LaTiOx with similar orthorhombic structure and cationic oxidation state. Experiment and theory show the expected upward shift in energy of the valence band maximum that reduces the band gap as a consequence of the nitrogen incorporation. This study also shows that the conduction band minimum, typically considered almost unaffected by nitrogen substitution, undergoes a significant downward shift in energy. For a rational design of oxynitride photocatalysts, the observed changes of both the unoccupied and occupied electronic states have to be taken into account to justify the total band-gap narrowing induced by the nitrogen incorporation.

Validation of Ru(II)‐caged Abiraterone as a Chemical Tool for Controlling CYP17A1 Activity with Visible Light

Cytochromes P450 (CYP) enzymes are ubiquitous heme‐containing proteins catalyzing numerous and varied biosynthetic and detoxification transformations in biological systems. Potent and selective inhibitors have been aggressively pursued as chemical tools, drugs, and insecticides, but lack spatial and temporal control over CYP inhibition in vitro and in vivo. Metal‐caged versions of such inhibitors with photoactivated release can allow researchers to interrogate biological systems spatiotemporally. Here, a novel Ru(II)‐caged complex was designed and synthesized with the CYP17A1 inhibitor abiraterone, a prostate cancer drug. While the intact caged complex is non‐toxic and exceptionally stable in the dark, upon irradiation with low energy visible light abiraterone is rapidly released. In the dark the Ru(II) caged abiraterone does not bind to CYP17A1, but light exposure results in the released abiraterone binding to CYP17A1. This binding is observed as a type II shift consistent with the inhibitor nitrogen coordinating to the CYP17A1 heme iron with a high affinity, similar to abiraterone itself. Additionally, dark Ru(II)‐abiraterone is nontoxic to DU145 human prostate cancer cells, but light‐exposed Ru(II)‐abiraterone and abiraterone resulted in similar toxicity. Overall, this demonstrates that metal‐caged inhibitors can be designed with ideal properties as potent and selective chemical tools controlled by visible light in a biological setting.Support or Funding InformationNIH (EB 016072) and NSF (CHE1212281)

Visible-light-enhanced photocatalytic Sonogashira reaction over silicon carbide supported Pd nanoparticles

Sonogashira reaction of aryl halides with terminal alkynes can be realized by a visible-light-driven heterogeneous catalytic route using silicon carbide supported Pd nanoparticles as the catalyst under copper-, and ligand-free conditions. Under the irradiation of visible light, the photo-generated electrons excited in SiC can quickly transfer to Pd nanoparticles through the Mott-Schottky contact, and make them electron-rich. The electrons of Pd particles become energetic by absorbing the energy of visible light, and then transfer to halogen atoms to facilitate the cleavage of carbon-halogen bond in aryl halides. The final carbon-carbon formation is achieved by the substitution reaction and reductive elimination processes.

Metal-Organic Framework Photosensitized TiO2 Co-catalyst: A Facile Strategy to Achieve a High Efficiency Photocatalytic System.

A 3D metal-organic framework (ADA-Cd=[Cd2 L2 (DMF)2 ]⋅3 H2 O where H2 L is (2E,2'E)-3,3'-(anthracene-9,10-diyl)diacrylic acid) constructed from diacrylate substituted anthracene, sharing structural characteristics with some frequently employed anthraquinone-type dye sensitizers, was introduced as an effective sensitizer for anatase TiO2 to achieve enhanced visible light photocatalytic performance. A facile mechanical mixing procedure was adopted to prepare the co-catalyst denoted as ADA-Cd/TiO2 , which showed enhanced photodegradation ability, as well as sustainability, towards several dyes under visible light irradiation. Mechanistic studies revealed that ADA-Cd acted as the antenna to harvest visible light energy, generating excited electrons, which were injected to the conduction band (CB) of TiO2 , facilitating the separation efficiency of charge carriers. As suggested by the results of control experiments, combined with the corresponding redox potential of possible oxidative species, . O2- , generated from the oxygen of ambient air at the CB of TiO2 was believed to play a dominant role over . OH and h+ . UV/Vis and photoluminescence technologies were adopted to monitor the generation of . O2- and . OH, respectively. This work presents a facile strategy to achieve a visible light photocatalyst with enhanced catalytic activity and sustainability; the simplicity, efficiency, and stability of this strategy may provide a promising way to achieve environmental remediation.