Light Energy Conversion Research Articles

Anthraquinone-Catalyzed Photooxidation of Boronic Acids in a Bio-Based Solvent (2-Me-THF)

AbstractThe phenol moiety appears in a wide variety of natural products, exhibiting biological activity, and in numerous active pharmaceutical compounds. Boronic acids are potential precursors of the phenol scaffold, and a plethora of efforts has been focused in developing novel and green protocols, targeting their chemoselective transformation into phenols. Photochemistry is a rapidly expanding research field converting light energy into chemical potential. Photochemical aerobic processes possess additional advantages to photochemistry and may find applications in chemical industries. Herein, a low-catalyst-loading anthraquinone-catalyzed photochemical process is demonstrated, under CFL lamp irradiation, while exploiting 2-Me-THF as the reaction medium for the conversion of boronic acids into phenols. Furthermore, a broad substrate scope was employed.

Hierarchical porous photosensitizers with efficient photooxidation

Photosensitizers (PSs) with nano- or micro-sized pore provide a great promise in the conversion of light energy into chemical fuel due to the excellent promotion for transporting singlet oxygen (1O2) into active sites. Despite such hollow PSs can be achieved by introducing molecular-level PSs into porous skeleton, however, the catalytic efficiency is far away from imagination because of the problems with pore deformation and blocking. Here, very ordered porous PSs with excellent 1O2 generation are presented from cross-linking of hierarchical porous laminates originated by co-assembly of hydrogen donative PSs and functionalized acceptor. The catalytic performance strongly depends on the preformed porous architectures, which is regulated by special recognition of hydrogen binding. As the increasing of hydrogen acceptor quantities, 2D-organized PSs laminates gradually transform into uniformly perforated porous layers with highly dispersed molecular PSs. The premature termination by porous assembly endows superior activity as well as specific selectivity for the photo-oxidative degradation, which contributes to efficient purification in aryl-bromination without any postprocessing.

Applications of single laser pulse from Nd:doped lasers for cleaning of small diameter carious lesions. Modelling and analytical study

We report on an analytical study with physical modelling, some additional experimental studies and computer programming of the cleaning of initial carious lesions (1 - 3 mm in diameter) with a single laser pulse from Nd:doped (Nd:YAG and Nd:Glass) lasers (wavelength 1.06 μm). The analysis is based on experimental data from our preliminary study and aims to develop a method to predetermine the necessary laser pulse parameters for reasonable cleaning. To obtain such laser pulse parameters, we considered the conversion of light energy into heat, the propagation of incident light and the resulting heating of the dental tissue, the induced ablation processes associated with lesion cleaning, and the formation of the necessary hole in combination with acceptable heating of the pulp chamber and prevention of enamel crack formation. Cleaning is naturally associated with the bactericidal effect. The study, except for the estimation, confirms that the use of single light pulses of the considered lasers with energies from 1.3 to 4.5 J, densities from 40 to 120 J/cm2, pulse duration from a few hundred microseconds to ~2 ms (i.e., in the simplest, natural, free mode of operation of the noted lasers) can be considered as a promising method to start caries treatment.

Effects of Graphene Oxide on the Growth and Photosynthesis of the Emergent Plant Iris pseudacorus.

The extensive applications of graphene oxide (GO) inevitably lead to entry into the natural aquatic environment. However, information on its toxicity to emergent plants is still lacking. In this study, an emergent plant, Iris pseudacorus, was exposed to GO (1, 20, 80, and 140 mg·L-1) under hydroponic conditions for 15 weeks. Changes in plant growth were assessed by analyzing plant biomass and photosynthetic pigment contents; the photosynthesis response was verified by measuring chlorophyll a fluorescence; and the nutrient levels of the plant were evaluated. Results showed that GO at 20-140 mg·L-1 significantly increased plant dry weight by 37-84% and photosynthetic pigment contents by 26-178%, and 80 mg·L-1 was the optimal concentration. PSII activity, adjustment capacities of electron transport in PSII, the grouping or energetic connectivity between PSII units, light energy conversion efficiency, photosynthesis performance indexes (by 11-51%), and contents of several nutrient elements (N, Fe, and Cu) were increased by 49-69%, 34-84%, and 11-38%, respectively. These findings indicate that GO can enhance plant growth by promoting plant photosynthesis performance and improving plant nutrient levels, and has great application potential in promoting the growth and development of this emergent plant as a phytoremediation agent.

Achieving improved full-spectrum responsive 0D/3D CuWO4/BiOBr:Yb3+,Er3+ photocatalyst with synergetic effects of up-conversion, photothermal effect and direct Z-scheme heterojunction

The key to obtain effective photocatalysts is to increase the efficiency of light energy conversion, and thus the design and implementation of full-spectrum photocatalysts is a potential approach to solve this problem especially by extending the absorption range to near-infrared (NIR) light. Herein, the improved full-spectrum responsive CuWO4/BiOBr:Yb3+,Er3+ (CW/BYE) direct Z-scheme heterojunction was prepared. The CW/BYE with CW mass ratio of 5% had the best degradation performance, and the removal rate of tetracycline reached 93.9% in 60 min and 69.4% in 12 h under visible (Vis) and NIR light, respectively, which were 5.2 and 3.3 times of BYE. According to the outcome of experimental, the reasonable mechanism of improved photoactivity was put forward on the basis of (i) the up-conversion (UC) effect of Er3+ ion to convert NIR photon to ultraviolet or visible light, which can be used by CW and BYE, (ii) the photothermal effect of CW to absorb the NIR light, increasing the local temperature of photocatalyst particle to accelerate the photoreaction, and (iii) the formed direct Z-scheme heterojunction between BYE and CW to boost the separation of photogenerated electron-hole pairs. Additionally, the excellent photostability of the photocatalyst was verified by cycle degradation experiments. This work opens up a promising technique for designing and synthesizing full-spectrum photocatalysts by utilizing synergetic effects of UC, photothermal effect and direct Z-scheme heterojunction.

Superior triethylamine sensing platform based on MOF activated by carbon dots for photoelectric dual-mode in biphasic system

Multimode sensors are required to enable detect of hazardous substances in different media. A sensing platform based on metal organic frameworks (MOF) and its derivatives was established to detect triethylamine (TEA) gas and TEA aqueous solution in the range of 1–100 ppm. The carbon dots (CDs) were selected as the light-energy conversion module to improve greatly the photoelectric performance of sensors. On the one hand, the dual-emission ratio type fluorescent sensor was built by CDs and MOF. The CDs@ZIF-8(In) showed excellent fluorescence emission enhancement at 440 nm and 610 nm in a dose-dependent manner when TEA was added. The change of fluorescence emission intensity of CDs@ZIF-8(In) sensor for TEA in water was at least 3 times than that of other volatile organic compounds, and its detection limit reached 1 ppm. On the other hand, the gas sensor based on MOF derivatives modified by CDs (CDs@DZIF-8(In)) displayed 3.5 times signal response than pure DZIF-8(In), reaching 374.6 to 100 ppm TEA. Moreover, the optimal operating temperature of CDs@DZIF-8(In) sensor was 40 ℃ lower than that of DZIF-8(In) sensor. The excellent fluorescence and electron transfer properties of CDs may play a key role in the design and modification of various types of sensors.

Solar water splitting Pt-nanoparticle photosystem I thylakoid systems: Catalyst identification, location and oligomeric structure

Photosynthetic conversion of light energy into chemical energy occurs in sheet-like membrane-bound compartments called thylakoids and is mediated by large integral membrane protein-pigment complexes called reaction centers (RCs). Oxygenic photosynthesis of higher plants, cyanobacteria and algae requires the symbiotic linking of two RCs, photosystem II (PSII) and photosystem I (PSI), to split water and assimilate carbon dioxide. Worldwide there is a large research investment in developing RC-based hybrids that utilize the highly evolved solar energy conversion capabilities of RCs to power catalytic reactions for solar fuel generation. Of particular interest is the solar-powered production of H2, a clean and renewable energy source that can replace carbon-based fossil fuels and help provide for ever-increasing global energy demands. Recently, we developed thylakoid membrane hybrids with abiotic catalysts and demonstrated that photosynthetic Z-scheme electron flow from the light-driven water oxidation at PSII can drive H2 production from PSI. One of these hybrid systems was created by self-assembling Pt-nanoparticles (PtNPs) with the stromal subunits of PSI that extend beyond the membrane plane in both spinach and cyanobacterial thylakoids. Using PtNPs as site-specific probe molecules, we report the electron microscopic (EM) imaging of oligomeric structure, location and organization of PSI in thylakoid membranes and provide the first direct visualization of photosynthetic Z-scheme solar water-splitting biohybrids for clean H2 production.

Prashant Kamat to give 2023 Crano Memorial Lecture

Prashant V. Kamat , the Rev. John A. Zahm, C.S.C., Professor of Science in the Department of Chemistry and Biochemistry and Radiation Laboratory at the University of Notre Dame, will present the 2023 Crano Memorial Lecture. Kamat was selected in recognition of his nearly 4 decades of work building bridges between physical chemistry and material science to develop advanced nanomaterials that promise cleaner and more efficient light energy conversion. He will give two lectures at the University of Akron on April 14. The afternoon talk is titled “Light Energy Conversion with Halide Perovskite-Molecular Hybrids. Energy versus Electron Transfer” and the evening talk is titled “Reducing Carbon Footprint with Next Generation Photovoltaics.” The Crano Memorial Lecture Series is organized by the ACS Akron Section in memory of John C. Crano, a past chair of the section and developer at PPG Industries of photochromic polymer lenses for eyeglasses.

A small dynamic leaf-level model predicting photosynthesis in greenhouse tomatoes.

The conversion of supplemental greenhouse light energy into biomass is not always optimal. Recent trends in global energy prices and discussions on climate change highlight the need to reduce our energy footprint associated with the use of supplemental light in greenhouse crop production. This can be achieved by implementing "smart" lighting regimens which in turn rely on a good understanding of how fluctuating light influences photosynthetic physiology. Here, a simple fit-for-purpose dynamic model is presented. It accurately predicts net leaf photosynthesis under natural fluctuating light. It comprises two ordinary differential equations predicting: 1) the total stomatal conductance to CO2 diffusion and 2) the CO2 concentration inside a leaf. It contains elements of the Farquhar-von Caemmerer-Berry model and the successful incorporation of this model suggests that for tomato (Solanum lycopersicum L.), it is sufficient to assume that Rubisco remains activated despite rapid fluctuations in irradiance. Furthermore, predictions of the net photosynthetic rate under both 400ppm and enriched 800ppm ambient CO2 concentrations indicate a strong correlation between the dynamic rate of photosynthesis and the rate of electron transport. Finally, we are able to indicate whether dynamic photosynthesis is Rubisco or electron transport rate limited.

Ultrasensitive Photoelectrochemical Immunoassay Strategy Based on Bi2S3/Ag2S for the Detection of the Inflammation Marker Procalcitonin

As an inflammatory marker, procalcitonin (PCT) is more representative than other traditional inflammatory markers. In this work, a highly efficient photoelectrochemical (PEC) immunosensor was constructed based on the photoactive material Bi2S3/Ag2S to realize the sensitive detection of PCT. Bi2S3 was prepared by a hydrothermal method, and Ag2S quantum dots were deposited on the ITO/Bi2S3 surface via in situ reduction. Bi2S3 is a kind of admirable photoelectric semiconductor nanomaterial on account of its moderate bandgap width and low binding rate of photogenerated electron holes, which can effectively convert light energy into electrical energy. Therefore, based on the energy level matching principle of Bi2S3 and Ag2S, a labeled Bi2S3/Ag2S PEC immunosensor was constructed, and the sensitive detection of PCT was successfully established. The linear detection range of the PEC immunosensor was 0.50 pg∙mL-1 to 50 ng∙mL-1, and the minimum detection limit was 0.18 pg∙mL-1. Compared with the traditional PEC strategy, the proposed PEC immunosensor is simple, convenient, and has good anti-interference, sensitivity, and specificity, which could provide a meaningful theoretical basis and reference value for the clinical detection of PCT.

Copper stress-induced phytotoxicity associated with photosynthetic characteristics and lignin metabolism in wheat seedlings

Copper (Cu) pollution is one of environmental problems that adversely affects the growth and development of plants. However, knowledge of lignin metabolism associated with Cu-induced phytotoxicity mechanism is insufficient. The objective of this study was to reveal the mechanisms underlying Cu-induced phytotoxicity by evaluating changes in the photosynthetic characteristics and lignin metabolism in the seedlings of wheat cultivar ‘Longchun 30′. Treatment with varying concentrations of Cu clearly retarded seedling growth, as demonstrated by a reduction in the growth parameters. Cu exposure reduced the photosynthetic pigment content, gas exchange parameters, and chlorophyll fluorescence parameters, including the maximum photosynthetic efficiency, potential efficiency of photosystem II (PS II), photochemical efficiency of PS II in light, photochemical quenching, actual photochemical efficiency, quantum yield of PS II electron transport, and electron transport rate, but notably increased the nonphotochemical quenching and quantum yield of regulatory energy dissipation. Additionally, a significant increase was observed in the amount of cell wall lignin in wheat leaves and roots under Cu exposure. This increase was positively associated with the up-regulation of enzymes related to lignin synthesis, such as phenylalanine ammonia-lyase, 4-coumarate:CoA ligase, cinnamyl alcohol dehydrogenase, laccase, cell wall bound (CW-bound) guaiacol peroxidase, and CW-bound conifer alcohol peroxidase, and TaPAL, Ta4CL, TaCAD, and TaLAC expression. Correlation analysis revealed that lignin levels in the cell wall were negatively correlated with the growth of wheat leaves and roots. Taken together, Cu exposure inhibited photosynthesis in wheat seedlings, resulting from a reduction in photosynthetic pigment content, light energy conversion, and photosynthetic electron transport in the leaves of Cu-stressed seedlings, and the Cu-inhibitory effect on seedling growth was related to the inhibition of photosynthesis and an increase in cell wall lignification.

Ultrafast motion in a third generation photomolecular motor

Controlling molecular translation at the nanoscale is a key objective for development of synthetic molecular machines. Recently developed third generation photochemically driven molecular motors (3GMs), comprising pairs of overcrowded alkenes capable of cooperative unidirectional rotation offer the possibility of converting light energy into translational motion. Further development of 3GMs demands detailed understanding of their excited state dynamics. Here we use time-resolved absorption and emission to track population and coherence dynamics in a 3GM. Femtosecond stimulated Raman reveals real-time structural dynamics as the excited state evolves from a Franck-Condon bright-state through weakly-emissive dark-state to the metastable product, yielding new insight into the reaction coordinate. Solvent polarity modifies the photoconversion efficiency suggesting charge transfer character in the dark-state. The enhanced quantum yield correlates with suppression of a low-frequency flapping motion in the excited state. This detailed characterization facilitates development of 3GMs, suggesting exploitation of medium and substituent effects to modulate motor efficiency.

Biomimetic photosynthetic system: Shedding light on the restoration of cell metabolism

Biomimetic photosynthetic system: Shedding light on the restoration of cell metabolism

Semiconductors-based Z-scheme materials for photoelectrochemical water splitting: A review

Photoelectrochemical (PEC) water splitting is among the most promising approaches for a potentially clean and renewable source for hydrogen fuel from the splitting of water into hydrogen and oxygen using light source and energy conversion due to its practical efficiency. The innovative approach is the construction of a two-step photoexcitation system, often called a Z-scheme photocatalysis system, which mimics natural photosynthesis. The PEC splitting of water using various Z-scheme materials is initiated by the direct absorption of a photon, which creates separated electrons and holes in the energy band gap of the material. A Z-scheme system employs two photocatalysts, one producing H2 and the other O2, usually with the aid of an electron shuttle. This review focuses on the current state of research on nanoscale-enhanced Z-scheme photocatalyst materials for the water splitting reaction. Additionally, the recent advances achieved in especially metal oxides, metal sulfides, g-C3N4, and semiconductors-based Z-scheme materials as photocatalyst systems for water-splitting, are also covered.

Photocatalytic C-O Coupling Enzymes That Operate via Intramolecular Electron Transfer.

Efficient and environmentally friendly conversion of light energy for direct utilization in chemical production has been a long-standing goal in enzyme design. Herein, we synthesized artificial photocatalytic enzymes by introducing an Ir photocatalyst and a Ni(bpy) complex to an optimal protein scaffold in close proximity. Consequently, the enzyme generated C-O coupling products with up to 96% yields by harvesting visible light and performing intramolecular electron transfer between the two catalysts. We systematically modulated the catalytic activities of the artificial photocatalytic cross-coupling enzymes by tuning the electrochemical properties of the catalytic components, their positions, and distances within a protein. As a result, we discovered the best-performing mutant that showed broad substrate scopes under optimized conditions. This work explicitly demonstrated that we could integrate and control both the inorganic and biochemical components of photocatalytic biocatalysis to achieve high yield and selectivity in valuable chemical transformations.

Solar Tracker: Performance Analysis and Optimisation of Efficiency

Solar energy is one of the richest source of renewable energy on Earth, thus its harnessing is very much necessary for the useful conversion of light energy into electric energy. Solar panels are developed in this direction. Many scientists have developed various methods to gather the solar irradiation in order to maximize the extraction of electric power from the Photovoltaic generators. However, the problem with the solar power is that it is directly dependent on light intensity. The main hindrance with solar panels is their low efficiency with huge investment. Studies show that a solar panel converts 20-40% of energy incident on it to electrical energy. The solution is to use a tracking system1, 7 that maintains the panel’s position orthogonal with the light source. There are many tracking systems designs available including passive and active systems with one or two axes of freedom.8, 9 It has been found that the overall efficiency gain in single-axis solar tracker designed in10 is 27% than that of fixed mechanism. We had optimised the tracker efficiency by performing the experiment with solar tracker for consecutive three days and thus results were analysed by using stat-ease software. Moreover, the testing showed that the power used by the tracking system was much less than that of power gained by tracking system. While working on the developed set-up, focus was given on the incremental efficiency of the solar power generation system. In the present work, further performance analysis is taken up with the help of various parameters viz. Specific Energy Production (SEP), Performance Ratio (PR), Ground Cover Ratio (GCR) and Surface Performance Ratio (SPR)11 to further elaborate the efficiency enhancement in solar trackers as compared to fixed systems.

Enhanced Luminescent Performance via Passivation of Surface Undercoordinated Pb Atoms in a CsPbBr3 Microplate

AbstractPerovskite materials are widely used in the fields of luminescence and light energy conversion with the advantages of low cost and outstanding optoelectronic properties. However, abundant surface lattice defects heavily affect the performances of perovskite optoelectronic devices. Here, by treating surface defects with oleylamine molecules in situ, the surface trap states are significantly decreased in a CsPbBr3 microplate, enabling photoluminescence intensity and carrier lifetimes to be dramatically enhanced and prolonged, respectively. These interesting phenomena can be attributed to the binding of undercoordinated Pb atoms with N atoms on the surface of perovskite microplate. The strong binding energy of lead‐halogen bonds inhibits the photodegraded reactions of the crystal, leading to the significant improvement of luminescent stability for the microplate correspondingly. The results not only provide experimental guidance for passivating lattice defects but also pave the way for improving the efficiency of wide materials and optoelectronic devices.

The development of live microorganism-based oxygen shuttles for enhanced hypoxic tumor therapy.

Hypoxia is a prominent feature of malignant tumors and contributes to tumor proliferation, metastasis, and drug resistance in various solid tumors. Therefore, improving tumor oxygenation is crucial for curing tumors. To date, multiple strategies, including oxygen delivering and producing materials, have been designed to increase the oxygen concentration in hypoxic tumors. However, the unsustainable supply of oxygen is still the main obstacle, resulting in a suboptimal outcome in treating oxygen-deprived tumors. Thus, a sufficient oxygen supply is highly desirable in the treatment of hypoxic tumors. Photosynthesis, as the main source of oxygen in nature through the conversion of light energy into chemical energy and oxygen, has been widely studied in scientific research. Moreover, photosynthetic microorganisms have been increasingly applied in cancer therapy by increasing oxygenation, which improves the therapeutic effect of oxygen-consuming tumor therapeutic tools such as radiotherapy and photodynamic therapy. In this review, we summarize recent advances in the design and manufacture of live bacteria as oxygen shuttles for a new generation of hypoxic tumor treatment strategies. Finally, current challenges and future directions are also discussed for successfully addressing hypoxic tumor issues.

Rational design of ultrafast PpcA-Ru(bpy)3 complexes.

Converting light energy into its electrochemical equivalent requires precise control and fine-tuning of relevant kinetic and thermodynamic parameters of electron transfer (ET) steps. A particularly big challenge for artificial photosynthesis is to create the primary charge separation on the ultrafast (sub-nanosecond) time scale, as slower reactions are likely to require precious metal photosensitizers and produce significant amounts of reactive oxygen species. However, the structural requirements for ultrafast ET are poorly understood. The previous work from our lab has demonstrated that ET rates do not strictly depend on the distances. Similarly, we have demonstrated that short ET pathways through covalent bonds do not always result in ultrafast ET. We hypothesize that a rigid attachment of photosensitizers and efficient heat dissipation into the protein framework are needed for ultrafast ET. To test this hypothesis, we developed 13 new mutant forms of PpcA with the attachment cysteine sites showing restricted solvent exposure. We successfully labeled 11 out of 13 with Ru(bpy)3 and observed the expected complex masses in LC-MS. Analytical size-exclusion chromatography revealed the absence of aggregation and predominantly monomeric forms. Temperature-dependent circular dichroism (CD) spectroscopy showed the absence of any significant destabilization of the protein structure due to mutations and photosensitizer attachment, aside from I38CRu. Finally, we measured electron transfer rates that show that 10 of the 11 labeled PpcA-Ru(bpy)3 complexes show ultra-fast electron transfer.

Synergetic effect evaluation of light and mass transfer enhancement strategies on photo fermentative biohydrogen production process: Illumination, shake, and high solid level

During the process of photo fermentative biohydrogen production (PFHP) with high substrate concentration from agricultural waste, the interphase light and mass transfer behavior is hindered, caused by the suspension flow of substrates, resulting in low hydrogen production performance. In the paper, shake and lighting supplied strategy was investigated to soften the restrictions of high substrate concentration of corncob to improve the hydrogen yield and light energy conversion. The response surface methodology (RSM) was adopted to optimize the influence of variables on hydrogen production (substrate concentration, light intensity and shake intensity). Results showed that the maximum hydrogen yield of 48 mL/g TS and the maximum light energy conversion efficiency of 11.04% were obtained at the condition of 150 rpm, 6000 Lux and substrate concentration 55.56 g/L, increased by 603.85% and 598.63% than the static condition, respectively. RSM showed the synergistic effect between variables significantly affected the hydrogen production performance, the optimal enhancement strategies were: shake intensity 153.33 rpm, light intensity 6155.56 Lux and substrate concentration 57.71 g/L. 4.71% error of the predicted cumulative hydrogen yield (490.41 mL) and the actual cumulative hydrogen yield (468.34 mL) indicating the fitting effect of the model was satisfactory.