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Annual Review of Physical Chemistry 2014The recombination of electrons and holes is a major loss mechanism in photovoltaic devices that controls their performance. We review scientific literature on... (Review)
Review
The recombination of electrons and holes is a major loss mechanism in photovoltaic devices that controls their performance. We review scientific literature on bimolecular recombination (BR) in bulk heterojunction organic photovoltaic devices to bring forward existing ideas on the origin and nature of BR and highlight both experimental and theoretical work done to quantify its extent. For these systems, Langevin theory fails to explain BR, and recombination dynamics turns out to be dependent on mobility, temperature, electric field, charge carrier concentration, and trapped charges. Relationships among the photocurrent, open-circuit voltage, fill factor, and morphology are discussed. Finally, we highlight the recent emergence of a molecular-level picture of recombination, taking into account the spin and delocalization of charges. Together with the macroscopic picture of recombination, these new insights allow for a comprehensive understanding of BR and provide design principles for future materials and devices.
Topics: Electronics; Electrons; Fullerenes; Light; Photochemistry; Semiconductors
PubMed: 24423376
DOI: 10.1146/annurev-physchem-040513-103615 -
Water Research May 2010In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align... (Review)
Review
In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align with the "zero" waste scheme in the water/wastewater industry. The ability of this advanced oxidation technology has been widely demonstrated to remove persistent organic compounds and microorganisms in water. At present, the main technical barriers that impede its commercialisation remained on the post-recovery of the catalyst particles after water treatment. This paper reviews the recent R&D progresses of engineered-photocatalysts, photoreactor systems, and the process optimizations and modellings of the photooxidation processes for water treatment. A number of potential and commercial photocatalytic reactor configurations are discussed, in particular the photocatalytic membrane reactors. The effects of key photoreactor operation parameters and water quality on the photo-process performances in terms of the mineralization and disinfection are assessed. For the first time, we describe how to utilize a multi-variables optimization approach to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency. Both photomineralization and photo-disinfection kinetics and their modellings associated with the photocatalytic water treatment process are detailed. A brief discussion on the life cycle assessment for retrofitting the photocatalytic technology as an alternative waste treatment process is presented. This paper will deliver a scientific and technical overview and useful information to scientists and engineers who work in this field.
Topics: Catalysis; Photochemistry; Waste Disposal, Fluid; Water Purification
PubMed: 20378145
DOI: 10.1016/j.watres.2010.02.039 -
Advances in Biochemical... 2016A more complete understanding of bioelectrochemical interfaces is of increasing importance in both fundamental studies and biotechnological applications of proteins.... (Review)
Review
A more complete understanding of bioelectrochemical interfaces is of increasing importance in both fundamental studies and biotechnological applications of proteins. Bioelectrochemical methods provide detailed information about the activity or rate of a process, but in situ spectroscopic methods are needed to gain direct structural insight into functionally relevant states. A number of methods have been reported that allow electrochemical and spectroscopic data to be collected from the same electrode, providing direct spectroscopic 'snapshots' of protein function, and here we focus on the application of infrared and Raman spectroscopies to the study of electrode-immobilised species. The ability to probe coordination at metal centres, protonation changes in amino acid side chains, reaction-induced changes in organic cofactors or substrates, protein orientation and subtle changes in protein secondary structure simultaneously, rapidly and at room temperature means that vibrational spectroscopic approaches are almost uniquely applicable to answering a wide range of questions in bioelectrochemistry.
Topics: Catalysis; Electrochemistry; Photochemistry; Proteins; Spectrum Analysis; Vibration
PubMed: 27475648
DOI: 10.1007/10_2016_3 -
Nanoscale Jan 2015Graphitic carbon nitride (g-C(3)N(4)), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical... (Review)
Review
Graphitic carbon nitride (g-C(3)N(4)), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C(3)N(4) suffers from rapid recombination of photo-generated electron-hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C(3)N(4) could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C(3)N(4)-based nanocomposites can be classified and summarized: namely, the g-C(3)N(4) based metal-free heterojunction, the g-C(3)N(4)/single metal oxide (metal sulfide) heterojunction, g-C(3)N(4)/composite oxide, the g-C(3)N(4)/halide heterojunction, g-C(3)N(4)/noble metal heterostructures, and the g-C(3)N(4) based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C(3)N(4)-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C(3)N(4)-based nanocomposites. The unique functions of the p-n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C(3)N(4)-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C(3)N(4)-based advanced nanomaterials.
Topics: Catalysis; Electric Power Supplies; Electrodes; Equipment Design; Graphite; Light; Nanocomposites; Nitriles; Particle Size; Photochemistry; Semiconductors
PubMed: 25407808
DOI: 10.1039/c4nr03008g -
Annual Review of Physical Chemistry 2013Molecular switches and motors respond structurally, electronically, optically, and/or mechanically to external stimuli, testing and potentially enabling extreme... (Review)
Review
Molecular switches and motors respond structurally, electronically, optically, and/or mechanically to external stimuli, testing and potentially enabling extreme miniaturization of optoelectronic devices, nanoelectromechanical systems, and medical devices. The assembly of motors and switches on surfaces makes it possible both to measure the properties of individual molecules as they relate to their environment and to couple function between assembled molecules. In this review, we discuss recent progress in assembling molecular switches and motors on surfaces, measuring static and dynamic structures, understanding switching mechanisms, and constructing functional molecular materials and devices. As demonstrative examples, we choose a representative molecule from three commonly studied classes including molecular switches, photochromic molecules, and mechanically interlocked molecules. We conclude by offering perspectives on the future of molecular switches and motors on surfaces.
Topics: Electric Conductivity; Electronics; Miniaturization; Models, Molecular; Photochemistry; Polymers; Surface Properties
PubMed: 23331305
DOI: 10.1146/annurev-physchem-040412-110045 -
Photochemistry and Photobiology Jan 1971
Topics: History, 20th Century; Photochemistry; United States
PubMed: 4926148
DOI: 10.1111/j.1751-1097.1971.tb06085.x -
Chemical Society Reviews May 2014This review covers the advances made in the synthesis of luminescent transition metal complexes containing N-heterocyclic carbene (NHC) ligands. The presence of a high... (Review)
Review
This review covers the advances made in the synthesis of luminescent transition metal complexes containing N-heterocyclic carbene (NHC) ligands. The presence of a high field strength ligand such as an NHC in the complexes gives rise to high energy emissions, and consequently, to the desired blue colour needed for OLED applications. Furthermore, the great versatility of NHC ligands for structural modifications, together with the use of other ancillary ligands in the complex, provides numerous possibilities for the synthesis of phosphorescent materials, with emission colours over the entire visible spectra and potential future applications in fields such as photochemical water-splitting, chemosensors, dye-sensitised solar cells, oxygen sensors, and medicine.
Topics: Catalysis; Coordination Complexes; Luminescence; Methane; Photochemistry
PubMed: 24604135
DOI: 10.1039/c3cs60466g -
Journal of the American Chemical Society Jun 2023β-Lapachone is an -naphthoquinone natural product with significant antiproliferative activity but suffers from adverse systemic toxicity. The use of photoremovable...
β-Lapachone is an -naphthoquinone natural product with significant antiproliferative activity but suffers from adverse systemic toxicity. The use of photoremovable protecting groups to covalently inactivate a substrate and then enable controllable release with light in a spatiotemporal manner is an attractive prodrug strategy to limit toxicity. However, visible light-activatable photocages are nearly exclusively enabled by linkages to nucleophilic functional sites such as alcohols, amines, thiols, phosphates, and sulfonates. Herein, we report covalent inactivation of the electrophilic quinone moiety of β-lapachone via a C(sp)-C(sp) bond to a coumarin photocage. In contrast to β-lapachone, the designed prodrug remained intact in human whole blood and did not induce methemoglobinemia in the dark. Under light activation, the C-C bond cleaves to release the active quinone, recovering its biological activity when evaluated against the enzyme NQO1 and human cancer cells. Investigations into this report of a C(sp)-C(sp) photoinduced bond cleavage suggest a nontraditional, radical-based mechanism of release beginning with an initial charge-transfer excited state. Additionally, caging and release of the isomeric -quinone, α-lapachone, are demonstrated. As such, we describe a photocaging strategy for the pair of quinones and report a unique light-induced cleavage of a C-C bond. We envision that this photocage strategy can be extended to quinones beyond β- and α-lapachone, thus expanding the chemical toolbox of photocaged compounds.
Topics: Electron Spin Resonance Spectroscopy; Photochemistry; Humans; Models, Molecular; Cell Line, Tumor
PubMed: 37265114
DOI: 10.1021/jacs.3c00398 -
Advanced Materials (Deerfield Beach,... Sep 2023Patterning biomolecules in synthetic hydrogels offers routes to visualize and learn how spatially-encoded cues modulate cell behavior (e.g., proliferation,...
Patterning biomolecules in synthetic hydrogels offers routes to visualize and learn how spatially-encoded cues modulate cell behavior (e.g., proliferation, differentiation, migration, and apoptosis). However, investigating the role of multiple, spatially defined biochemical cues within a single hydrogel matrix remains challenging because of the limited number of orthogonal bioconjugation reactions available for patterning. Herein, a method to pattern multiple oligonucleotide sequences in hydrogels using thiol-yne photochemistry is introduced. Rapid hydrogel photopatterning of hydrogels with micron resolution DNA features (≈1.5 µm) and control over DNA density are achieved over centimeter-scale areas using mask-free digital photolithography. Sequence-specific DNA interactions are then used to reversibly tether biomolecules to patterned regions, demonstrating chemical control over individual patterned domains. Last, localized cell signaling is shown using patterned protein-DNA conjugates to selectively activate cells on patterned areas. Overall, this work introduces a synthetic method to achieve multiplexed micron resolution patterns of biomolecules onto hydrogel scaffolds, providing a platform to study complex spatially-encoded cellular signaling environments.
Topics: DNA; Signal Transduction; Hydrogels; Photochemistry
PubMed: 37221642
DOI: 10.1002/adma.202301086 -
Biosensors & Bioelectronics Dec 2004Sugar recognition in an aqueous system has been achieved using a boronic acid-diol interaction. Combination with an intramolecular amino group has enabled us to read out... (Review)
Review
Sugar recognition in an aqueous system has been achieved using a boronic acid-diol interaction. Combination with an intramolecular amino group has enabled us to read out the binding process as a change in the fluorescence intensity. The novel interaction has been extended to dynamic sugar sensing utilizing an allosteric effect, molecular imprinting, and control of molecular assemblies.
Topics: Biomimetics; Biosensing Techniques; Boronic Acids; Drug Design; Electrochemistry; Electron Transport; Glucose; Kinetics; Photochemistry; Receptors, Cell Surface; Spectrometry, Fluorescence; Stereoisomerism; Surface Properties
PubMed: 15556374
DOI: 10.1016/j.bios.2004.03.036