Excellent Light-harvesting Properties Research Articles

Vanadium-doped metal-organic framework@Znln2S4 core-shell heterojunction-attenuated photoelectrochemical immunoassay

Considering that cancer has become the second leading cause of death in humans, it is essential to develop an analytical approach that can sensitively detect tumor markers for early detection. We report an attenuated photoelectrochemical (PEC) immunoassay based on the organic-inorganic heterojunction 10MIL-88B(FeV)/ZnIn2S4 (10M88B(FeV)/ZIS) as a photoactive material for monitoring carcinoembryonic antigen (CEA). The 10M88B(FeV)/ZIS heterojunctions have excellent light-harvesting properties and high electrical conductivity, which are attributed to the advantages of both organic and inorganic semiconductors, namely, remarkable photogenerated carrier separation efficiency and long photogenerated carrier lifetime. Horseradish peroxidase (HRP) in the presence of H2O2 can catalyze 3,3′-diaminofenamide (DAB) producing brown precipitates (oxDAB), which is then loaded onto the 10M88B(FeV)/ZIS heterojunction to reduce the photocurrent and enable the quantitative detection of CEA. Under optimal conditions, the photocurrent values of the PEC biosensor are linearly related to the logarithm of the CEA concentrations, ranging from 0.01 ng mL−1 to 100 ng mL−1 with a detection limit (LOD) of 4.0 pg mL−1. Notably, the accuracy of the PEC biosensor is in agreement with that of the human CEA enzyme-linked immunosorbent assay (ELISA) kit.

Exploring a Ni-N4 Active Site-Based Conjugated Microporous Polymer Z-Scheme Heterojunction Through Covalent Bonding for Visible Light-Driven Photocatalytic CO2 Conversion in Pure Water.

Designing photocatalysts with efficient charge transport and abundant active sites for photocatalytic CO2 reduction in pure water is considered a potential approach. Herein, a nickel-phthalocyanine containing Ni-N4 active sites-based conjugated microporous polymer (NiPc-CMP), offering highly dispersed metal active sites, satisfactory CO2 adsorption capability, and excellent light harvesting properties, is engineered as a photocatalyst. By virtue of the covalently bonded bridge, an atomic-scale interface between the NiPc-CMP/Bi2 WO6 Z-scheme heterojunction withstrong chemical interactions is obtained. The interface creates directional charge transport highways and retains a high redox potential, thereby enhancing the photoexcited charge carrier separation and photocatalytic efficiency. Consequently, the optimal NiPc-CMP/Bi2 WO6 (NCB-3) achieves efficient photocatalytic CO2 reduction performance in pure water under visible-light irradiation without any sacrificial agent or photosensitizer, affording a CO generation rate of 325.9µmol g-1 with CO selectivity of 93% in 8h, outperforming those of Bi2 WO6 and NiPc-CMP, individually. Experimental and theoretical calculations reveal the promotion of interfacial photoinduced electron separation and the role of Ni-N4 active sites in photocatalytic reactions. This study presents a high-performance CMP-based Z-scheme heterojunction with an effective interfacial charge-transfer route and rich metal active sites for photocatalytic CO2 conversion.

Solar Light Responsive Graphitic Carbon Nitride Coupled Porphyrin Photocatalyst that Uses for Solar Fine Chemical Production.

Photocatalysis is a defendable manner for production of several organic chemicals, energy and its storage from solar energy. For the evolution of metal free, cost-effective catalyst a 2D composite has been appear as a photocatalyst. Here, we had reported the synthesis of a light harvesting composite as a photocatalyst which was assembled by a poly-condensation mechanism between graphitic carbon nitride and tetrakis(4-nitrophenyl) porphyrin and the resulting composite manifest the excellent light harvesting properties, suitable energy band and low charge recombination. The photocatalyst [(NO2 )4 TPP@g-C3 N4 ] enables the efficient photocatalytic production of nicotinamide adenine dinucleotide (NADH) from consumed NAD+ also the production of organic chemicals like 4-methoxybenzylimines from 4-methoxybenzylamines. The photocatalytic efficiency of the photocatalyst was estimated by the percentage of NADH regeneration and the percentage yield of organic transformations. It shows the tetrakis(4-nitrophenyl) porphyrin could enhance the charge transfer capacity of graphitic carbon nitride which shows excellent photocatalysis activities and organic transformations.

Organic Quasi-Liquid Schiff Bases from Biomolecules: Synthesis, Structure and Quantum Mechanical Studies

Phenylacetaldehyde, a naturally occurring plant-derived, occurs in vegetables and flowers during storage. We synthesized Schiff bases using phenylacetaldehyde and three natural biomolecules- adenine, cytosine, and l-leucine. We characterized them using various spectroscopic methods like FTIR, FT-NMR, UV-VIS, etc., followed by multiple theoretical tools. Detailed vibrational and electronic spectral explanations are reported using experimental and theoretically simulated spectra. The density functional theory analysis of molecules was optimized ground-state calculations using DFT/B3LYP method with 6-311G+ (2d, p) as a basis set, and this optimized structure undergoes electronic spectra were generated using energy calculations by TD-DFT/CAM-B3LYP method, 6-311G+ (2d, p) as a basis set with water as a solvent. Schiff base from cytosine was found to show excellent light-harvesting properties (86.51%). Analysis of wave function-based properties like electrostatic potential, ALIE, non-covalent interactions, etc., provide information about the reactivity and stability features. PASS and subsequent docking studies indicate that the first Schiff base shows DNA Lyase inhibition, and the other two show anti-eczematic properties.

Synthesis of three quasi liquid Schiff bases between hexanal and adenine, cytosine, and l-leucine, structural interpretation, quantum mechanical studies and biological activity prediction

Hexanal, a naturally phytochemical known to inhibit phospholipase-D and facilitates extension of shelf-life of fruits, vegetables and flower during storage. We attemped to synthesise three quasi liquid Schiff bases using hexanal as the aldehyde component and other three natural biomolecules like adenine, cytosine and l-leucine as the amine counterpart and characterised them using different spectroscopic methods like FTIR, FT-NMR, UV–VIS etc. Detailed vibrational and electronic spectral explanation are reported using experimental spectra and theoretically simulated spectra. The compound was optimised using DFT- B3LYP/6–311 + G(2d,p) and electronic spectra was generated using CAM-B3LYP functional and same basis sets. Schiff base from cytosine was found to show excellent light harvesting properties (99.99%). Analysis of wave function based properties like electrostatic potential, ALIE, non-covalent interactions etc provide information about the reactivity and stability features. PASS and subsequent docking studies predicts that the first Schiff base shows DNA Lyase inhibition and the other two shows anti-eczematic properties.

Enhancing the Light Coverage of Photosynthetic Bacteria to Augment Photosynthesis by Conjugated Polymer Nanoparticles.

By coating photosynthetic bacteria of Rhodopseudomonas palustris with conjugated polymers nanoparticles modified with positively charged peptide TAT (CPNs-TAT), a bio-optical hybrid composite of R. palustris/CPNs-TAT has been constructed. R. palustris/CPNs-TAT augments the light coverage of R. palustris to broaden the R. palustris absorption due to excellent light-harvesting properties of CPNs-TAT, especially in the ultraviolet region. It leads to converting ultraviolet light to visible light that could be absorbed by R. palustris, allowing antenna systems around the reaction center (RC) of the photosynthetic membrane to absorb more photons, thus photons are excited and transferred to the RC where the electron-hole separation occurs. Therefore, R. palustris/CPNs-TAT improves adenosine triphosphate (ATP) synthesis by increasing proton gradient, resulting in the enhancement of the photosynthetic activity. This effort combines synthetic light-harvesting materials with photosynthetic bacteria without complicated genetic techniques to obtain the hybrid bio-optical systems for augmenting photosynthesis beyond natural photosynthetic bacteria.

Cellulose as an Inert Scaffold in Plasmon-Assisted Photoregeneration of Cofactor Molecules.

Plasmonic nanoparticles exhibit excellent light-harvesting properties in the visible spectral range, which makes them a convenient material for the conversion of light into useful chemical fuel. However, the need for using surface ligands to ensure colloidal stability of nanoparticles inhibits their photochemical performance due to the insulating molecular shell hindering the carrier transport. We show that cellulose fibers, abundant in chemical functional groups, can serve as a robust substrate for the immobilization of gold nanorods, thus also providing a facile way to remove the surfactant molecules. The resulting functional composite was implemented in a bioinspired photocatalytic process involving dehydrogenation of sodium formate and simultaneous photoregeneration of cofactor molecules (NADH, nicotinamide adenine dinucleotide) using visible light as an energy source. By systematic screening of experimental parameters, we compare photocatalytic and thermocatalytic properties of the composite and evaluate the role of palladium cocatalyst.

Unravelling the Photocatalytic Behavior of All-Inorganic Mixed Halide Perovskites: The Role of Surface Chemical States.

Within the most mesmerizing materials in the world of optoelectronics, mixed halide perovskites (MHPs) have been distinguished because of the tunability of their optoelectronic properties, balancing both the light-harvesting efficiency and the charge extraction into highly efficient solar devices. This feature has drawn the attention of analogous hot topics as photocatalysis for carrying out more efficiently the degradation of organic compounds. However, the photo-oxidation ability of perovskite depends not only on its excellent light-harvesting properties but also on the surface chemical environment provided during its synthesis. Accordingly, we studied the role of surface chemical states of MHP-based nanocrystals (NCs) synthesized by hot-injection (H-I) and anion-exchange (A-E) approaches on their photocatalytic (PC) activity for the oxidation of β-naphthol as a model system. We concluded that iodide vacancies are the main surface chemical states that facilitate the formation of superoxide ions, O2●-, which are responsible for the PC activity in A-E-MHP. Conversely, the PC performance of H-I-MHP is related to the appropriate balance between band gap and a highly oxidizing valence band. This work offers new insights on the surface properties of MHP related to their catalytic activity in photochemical applications.

MoSx Quantum Dot-Modified Black Silicon for Highly Efficient Photoelectrochemical Hydrogen Evolution

Nanostructured black silicon (bSi) is widely used for solar water-splitting application due to the excellent light-harvesting properties and large surface area-to-volume ratio that favors photoelec...

Efficient Sunlight Harvesting by A4 β-Pyrrolic Substituted ZnII Porphyrins: A Mini-Review.

Dye-Sensitized Solar Cells (DSSCs) are a highly promising alternative to conventional photovoltaic silicon-based devices, due to the potential low cost and the interesting conversion efficiencies. A key-role is played by the dye, and porphyrin sensitizers have drawn great interest because of their excellent light harvesting properties mimicking photosynthesis. Indeed, porphyrins are characterized by strong electronic absorption bands in the visible region up to the near infrared and by long-lived π* singlet excited states. Moreover, the presence of four meso and eight β-pyrrolic positions allows a fine tuning of their photoelectrochemical properties through structural modification. Trans-A2BC push–pull ZnII porphyrins, characterized by a strong and directional electron excitation process along the push–pull system, have been extensively investigated. On the other hand, A4 β-pyrrolic substituted tetraaryl ZnII porphyrins, which incorporate a tetraaryl porphyrinic core as a starting material, have received lower attention, even if they are synthetically more attractive and show several advantages such as a more sterically hindered architecture and enhanced solubility in most common organic solvents. The present contribution intends to review the most prominent A4 β-substituted ZnII porphyrins reported in the literature so far for application in DSSCs, focusing on the strategies employed to enhance the light harvesting capability of the dye and on a comparison with meso-substituted analogs.

Novel conjugated organic polymers as candidates for visible-light-driven photocatalytic hydrogen production

Artificial photosynthesis aiming to capture and convert renewable solar energy into solar fuels (e.g., hydrogen, chemicals) provides a blueprint for sustainable and carbon-neutral world. In artificial photosynthesis, developing novel semiconductors for visible-light-driven photocatalytic water splitting is one of the most demanding challenges. Herein, we designed and explored two kinds of novel bipyridine-based covalent organic polymers, Bp-COP (2,2′-bipyridine-5,5′-diamine: Bp-NH2) and BpZn-COP (2,2′-bipyridine-5,5′-diamine Zn complex: Bp-Zn), both of which exhibit excellent light-harvesting properties with absorption edges expanding to larger than 600 nm and have appropriate band structures for water splitting. Polymers Bp-COP and BpZn-COP are found to enable efficient photocatalytic hydrogen production under visible light irradiation with Pt as the proton reduction cocatalyst. Further assembling conjugated organic polymers with TiO2 as charge transferring mediate can remarkably boost their photocatalytic activities to more than 8 times (1333 vs. 162 μmol g−1 h−1), giving an apparent quantum efficiency (AQE) of over 2.5% at the input wavelength of 420 nm. This work not only presents a methodology for designing and synthesizing novel organic-based polymers, but also provides promising candidates for potential applications in solar energy conversion.

Comparative Performance Study of Perovskite Solar Cell for Different Electron Transport Materials

In recent times, planar organo-metal halide perovskite solar cells (PSCs) achieved high power conversion efficiency (PCE > 22%). Mixed organic-inorganic halide perovskites, with excellent light harvesting properties, have evolved as a promising class of semiconductors for photovoltaics. In this work, compositional and electrical characterizations of materials used for different layers of PSC have been studied. One dimensional solar cell simulator wx-AMPS is used for numerical simulation of such devices and all simulations are done under AM1.5 illuminations and 300K temperature. Investigating the influences of thickness of electron transport material (ETM), hole transporting material (HTM) and absorber on the photovoltaic performance of PSCs, it is observed that, increase in thickness of perovskite (MAPbI3) results in the increase in PCE of solar cells, whereas increase in thickness of ETM layer results in decrease in the efficiency of the devices. The ETM plays a vital role on the performance of PSC. In this paper, for the first time performances of PSC for three different ETMs (TiO2, ZnO or SnO2) are calculated and analyzed simultaneously with the simulator wx-AMPS. The photovoltaic performances have been explored and efficiencies of 27.6%, 27.5% and 28.02% are reported for perovskite solar cells with TiO2, ZnO and SnO2 as ETM respectively for a specific thickness. Finally, this simulation study concludes that ZnO and SnO2 may be effective alternatives of the commonly used material, TiO2 as they are economically more potential and give somewhat better photovoltaic performance.
 Dhaka Univ. J. Sci. 66(2): 109-114, 2018 (July)

Self-Assembled Mesoporous Carbon Nitride with Tunable Texture for Enhanced Visible-Light Photocatalytic Hydrogen Evolution

Mesoporous carbon nitride with novel morphology has been successfully fabricated by using ionic liquid and supramolecular precursor cyanuric acid-melamine complex as the template and precursor, respectively. The texture of carbon nitride is controlled by adjusting the ionic liquid concentration and type. The results find that a disordered hollow carbon nitride box morphology with pores in the wall can be obtained under lower IL1 concentration. With increasing of ionic liquid content, the texture turns to be a layered structure. The disordered nanosheets and hollow tube with large pores in the shell can be fabricated by using IL-2 and IL-3 as templates, respectively. Besides, as-prepared mesoporous carbon nitride samples display the excellent light harvesting properties and fast separation rate of photogenerated carrier. Moreover, mesoporous carbon nitride CN-0.1 exhibits a higher photocatalytic hydrogen evolution rate (120.3 μmol h–1) under visible light irradiation owing to the special structure and the presence of multiple mesopores, which is approximately 25.6, 1.7 times as high as that of bulk carbon nitride calcined by melamine and CN, respectively. Furthermore, photocatalytic RhB degradation rate is enhanced by using CN-0.1 compared with pure CN. This method provides more insights into designing novel visible light driven photocatalysts by using ionic liquids.

Well-designed 3D ZnIn2S4 nanosheets/TiO2 nanobelts as direct Z-scheme photocatalysts for CO2 photoreduction into renewable hydrocarbon fuel with high efficiency

A 3-dimensional (3D) ZnIn2S4/TiO2 Z-scheme system has been designed and constructed for photocatalytic reduction of CO2 into renewable hydrocarbon fuels without the use of a solid-state electron mediator. The unique 3D morphology, achieved by assembling 2D ZnIn2S4 nanosheets onto 1D TiO2 nanobelts, not only provides large surface area but also improves the separation and transfer efficiency of photogenerated electrons and holes. The 3D ZnIn2S4/TiO2 Z-scheme photocatalysts show excellent light-harvesting properties demonstrated in photocatalytic reduction of CO2, resulting in generation of desired hydrocarbons. The CH4 production rate of the 3D ZnIn2S4/TiO2 can reach up to 1.135μmolg−1h−1, which is about 39-times higher than that of bare ZnIn2S4 (0.029μmolg−1h−1). The enhanced photocatalytic activity is attributed to effective separation of the charge carriers between ZnIn2S4 and TiO2 through the direct Z-scheme instead of a type-II heterojunction. The photogenerated electrons in TiO2 nanobelts recombine with the holes in ZnIn2S4 nanosheets, and the unrecombined electrons/holes on different active sites have stronger reduction/oxidation abilities, leading to higher photocatalytic activity for CO2 reduction.

Multinary I-III-VI2 and I2-II-IV-VI4 Semiconductor Nanostructures for Photocatalytic Applications.

Semiconductor nanostructures that can effectively serve as light-responsive photocatalysts have been of considerable interest over the past decade. This is because their use in light-induced photocatalysis can potentially address some of the most serious environmental and energy-related concerns facing the world today. One important application is photocatalytic hydrogen production from water under solar radiation. It is regarded as a clean and sustainable approach to hydrogen fuel generation because it makes use of renewable resources (i.e., sunlight and water), does not involve fossil fuel consumption, and does not result in environmental pollution or greenhouse gas emission. Another notable application is the photocatalytic degradation of nonbiodegradable dyes, which offers an effective way of ridding industrial wastewater of toxic organic pollutants prior to its release into the environment. Metal oxide semiconductors (e.g., TiO2) are the most widely studied class of semiconductor photocatalysts. Their nanostructured forms have been reported to efficiently generate hydrogen from water and effectively degrade organic dyes under ultraviolet-light irradiation. However, the wide band gap characteristic of most metal oxides precludes absorption of light in the visible region, which makes up a considerable portion of the solar radiation spectrum. Meanwhile, nanostructures of cadmium chalcogenide semiconductors (e.g., CdS), with their relatively narrow band gap that can be easily adjusted through size control and alloying, have displayed immense potential as visible-light-responsive photocatalysts, but the intrinsic toxicity of cadmium poses potential risks to human health and the environment. In developing new nanostructured semiconductors for light-driven photocatalysis, it is important to choose a semiconducting material that has a high absorption coefficient over a wide spectral range and is safe for use in real-world settings. Among the most promising candidates are the multinary chalcogenide semiconductors (MCSs), which include the ternary I-III-VI2 semiconductors (e.g., AgGaS2, CuInS2, and CuInSe2) and the quaternary I2-II-IV-VI4 semiconductors (e.g., Cu2ZnGeS4, Cu2ZnSnS4, and Ag2ZnSnS4). These inorganic compounds consist of environmentally benign elemental components, exhibit excellent light-harvesting properties, and possess band gap energies that are well-suited for solar photon absorption. Moreover, the band structures of these materials can be conveniently modified through alloying to boost their ability to harvest visible photons. In this Account, we provide a summary of recent research on the use of ternary I-III-VI2 and quaternary I2-II-IV-VI4 semiconductor nanostructures for light-induced photocatalytic applications, with focus on hydrogen production and organic dye degradation. We include a review of the solution-based methods that have been employed to prepare multinary chalcogenide semiconductor nanostructures of varying compositions, sizes, shapes, and crystal structures, which are factors that are known to have significant influence on the photocatalytic activity of semiconductor photocatalysts. The enhancement of photocatalytic performance through creation of hybrid nanoscale architectures is also presented. Lastly, views on the current challenges and future directions are discussed in the concluding section.

Temperature dependent optical properties of CH3NH3PbI3 perovskite by spectroscopic ellipsometry

Mixed organic-inorganic halide perovskites have emerged as a promising new class of semiconductors for photovoltaics with excellent light harvesting properties. Thorough understanding of the optical properties of these materials is important for photovoltaic device optimization and the insight this provides for the knowledge of energy band structures. Here we present an investigation of the sub-room temperature dependent optical properties of polycrystalline thin films of CH3NH3PbI3 perovskites that are of increasing interest for photovoltaics. The complex dielectric function of CH3NH3PbI3 in the energy range of 0.5–4.1 eV is determined between 77 K and 297 K using spectroscopic ellipsometry. An increase in optical permittivity as the temperature decreases is illustrated for CH3NH3PbI3. Optical transitions and critical points were analyzed using the energy dependent second derivative of these dielectric functions as a function of temperature.

Computed and Experimental Absorption Spectra of the Perovskite CH3NH3PbI3.

Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe-Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the "gap" is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.

Light‐Harvesting in Multichromophoric Rotaxanes

Two rotaxanes with benzyl ether axles and tetralactam wheels were synthesized through an anion template effect. They carry naphthalene chromophores attached to the stopper groups and a pyrene chromophore attached to the wheel. The difference between the two rotaxanes is represented by the connecting unit of the naphthyl chromophore to the rotaxane axle: a triazole or an alkynyl group. Both rotaxanes exhibit excellent light-harvesting properties: excitation of the naphthalene chromophores is followed by energy transfer to the pyrene unit with efficiency higher than 90% in both cases. This represents an example of light-harvesting function among chromophores belonging to mechanically interlocked components, that is, the axle and the wheel of the rotaxanes.

Synthesis of a new class of cyclometallated ruthenium(II) complexes and their application in dye-sensitized solar cells

Abstract We synthesized a new class of cyclometallated ruthenium(II) complexes, Ru(tctpy)(C^N)(NCS) ( 1 , 2 ), where C^N is a bidentate cyclometallating ligand such as 2-phenylpyridinato or 2-(4-(2-phenylethynyl)phenyl)pyridinato. Although these complexes exist as stereoisomers, the microwave synthetic technique yielded only one isomer. These compounds act as light sensitizers and have excellent light-harvesting properties, especially in the near-IR region. Therefore, they can be used in dye-sensitized solar cells (DSCs). A DSC sensitized with 2 shows a 10% incident photon-to-current conversion efficiency at 900 nm.