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Macromolecular Rapid Communications Jul 2017Recently, visible-light-regulated polymerization has been gaining popularity, as it opens a range of new opportunities for the synthesis of functional polymers and... (Review)
Review
Recently, visible-light-regulated polymerization has been gaining popularity, as it opens a range of new opportunities for the synthesis of functional polymers and materials. Here, the most recent developments in this field are summarized, which is the use of photocatalysts and catalyst-free approaches to mediate polymerization upon photoexcitation. These catalysts can transfer an electron or energy to activate an initiator. The recent achievements in light-regulated atom-transfer radical polymerization, reversible addition-fragmentation chain-transfer polymerization, ring-opening metathesis polymerization, cobalt-mediated radical polymerization, iodine-mediated radical polymerization, and living cationic polymerization are reviewed. Recent development in these fields have solved important challenges in polymer chemistry, such as the development of oxygen-tolerant polymerization, polymerization mediated by near-infrared, metal-free polymerization, and spatial-, temporal-, and sequence-controlled polymerization. Some applications of these techniques will be discussed, such as adapting the current photocatalytic systems to synthesize heterogeneous photocatalysts that act as recyclable photocatalysts and novel light-mediated approaches for surface functionalization of hybrid materials and living cells. Finally, the existing challenges in polymer chemistry that could be overcome by further development of light-mediated polymerization techniques are highlighted along with the future directions of this field.
Topics: Catalysis; Electrons; Energy Transfer; Light; Photochemistry; Polymerization; Polymers
PubMed: 28556363
DOI: 10.1002/marc.201700143 -
Photosynthesis Research Aug 2015At the invitation of Suleyman I. Allakhverdiev, I provide here a brief autobiography for this special issue that recognizes my service and research for the larger...
At the invitation of Suleyman I. Allakhverdiev, I provide here a brief autobiography for this special issue that recognizes my service and research for the larger international community of photosynthesis research.
Topics: History, 20th Century; History, 21st Century; Photochemistry; Photosynthesis; Research
PubMed: 25645566
DOI: 10.1007/s11120-015-0077-1 -
Small (Weinheim An Der Bergstrasse,... May 2007There are a variety of methods for synthesizing or fabricating one-dimensional (1D) nanostructures containing heterojunctions between different materials. Here we review... (Review)
Review
There are a variety of methods for synthesizing or fabricating one-dimensional (1D) nanostructures containing heterojunctions between different materials. Here we review recent developments in the synthesis and fabrication of heterojunctions formed between different materials within the same 1D nanostructure or between different 1D nanostructures composed of different materials. Structures containing 1D nanoscale heterojunctions exhibit interesting chemistry as well as size, shape, and material-dependent properties that are unique when compared to single-component materials. This leads to new or enhanced properties or multifunctionality useful for a variety of applications in electronics, photonics, catalysis, and sensing, for example. This review separates the methods into vapor-phase synthesis, solution-phase synthesis, template-based synthesis, and other approaches, such as lithography, electrospinning, and assembly. These methods are used to form a variety of heterojunctions, including segmented, core/shell, branched, or crossed, from different combinations of semiconductor, metal, carbon, and polymeric materials.
Topics: Crystallization; Electrochemistry; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanostructures; Nanotechnology; Particle Size; Photochemistry; Semiconductors; Surface Properties
PubMed: 17444570
DOI: 10.1002/smll.200600727 -
Science (New York, N.Y.) Jun 2017
Topics: Conservation of Natural Resources; Nanotechnology; Photochemical Processes; Photochemistry; Photons; Water Purification
PubMed: 28572352
DOI: 10.1126/science.aan5802 -
Nature Methods Oct 2009
Topics: Animals; Fluorescence; Humans; Luminescent Proteins; Photochemistry; Protein Engineering
PubMed: 19953681
DOI: 10.1038/nmeth1009-713 -
The Journal of Physical Chemistry. B Sep 2005We report on UV-vis absorption and picosecond emission studies of methyl 2-amino-4,5-dimethoxy benzoate in neutral water and complexed to alpha-, beta-, and...
We report on UV-vis absorption and picosecond emission studies of methyl 2-amino-4,5-dimethoxy benzoate in neutral water and complexed to alpha-, beta-, and gamma-cyclodextrin (CD). Upon encapsulation, the emission intensity and the fluorescence lifetime increase, indicating a hydrophobic effect of the nanocages on the photophysical behavior of the guest. beta-CD confinement shows the largest effect. The time-dependent frequency shift of the emission (approximately 720 cm(-1)) in beta-CD nanocavity is larger than the one observed in water (approximately 490 cm(-1)) due to the hydrophobic and polarity effect of the nanocage and reflects a strengthening of the intramolecular H-bond of the encapsulated dye upon electronic excitation. Anisotropy measurements indicate a free motion of the guest into the nanocavity. The observed results are relevant to the hydrophobic as well as hydrophilic interactions which govern photochemistry and photophysics of caged drugs, organic, and biological systems.
Topics: Anesthetics; Capsules; Kinetics; Models, Theoretical; Nanotechnology; Photochemistry; Spectrophotometry
PubMed: 16853289
DOI: 10.1021/jp0512457 -
Journal of the American Chemical Society Apr 2022Photomechanical molecular crystals are promising candidates for photoactuators and can potentially be implemented as smart materials in various fields. Here, we...
Photomechanical molecular crystals are promising candidates for photoactuators and can potentially be implemented as smart materials in various fields. Here, we synthesized a new molecular crystal, ()-3-(naphthalen-1-yl)acrylaldehyde malononitrile (()-), that can undergo a solid-state [2 + 2] photocycloaddition reaction under visible light (≥400 nm) illumination. ()- microcrystals containing symmetric twinned sealed cavities were prepared using a surfactant-mediated crystal seeded growth method. When exposed to light, the hollow microcrystals exhibited robust photomechanical motions, including bending and dramatic directional expansion of up to 43.1% elongation of the original crystal length before fragmentation due to the photosalient effect. The sealed cavities inside the microcrystals could store different aqueous dye solutions for approximately one month and release the solutions instantly upon light irradiation. A unique slow-fast-slow crystal elongation kinematic process was observed, suggesting significant molecular rearrangements during the illumination period, leading to an average anisotropic crystal elongation of 37.0% (±3.8%). The significant molecular structure and geometry changes accompanying the photocycloaddition reaction, which propels photochemistry to nearly 100% completion, also facilitate photomechanical crystal expansion. Our results provide a possible way to rationally design molecular structures and engineer crystal morphologies to promote more interesting photomechanical behaviors.
Topics: Crystallization; Engineering; Light; Molecular Structure; Photochemistry
PubMed: 35289609
DOI: 10.1021/jacs.1c12485 -
Philosophical Transactions. Series A,... Jan 2006Arranging periodic, or quasi-periodic, regions of differing refractive index in one, two, or three dimensions can form a unique class of mesoporous structures. These... (Review)
Review
Arranging periodic, or quasi-periodic, regions of differing refractive index in one, two, or three dimensions can form a unique class of mesoporous structures. These structures are generally known as photonic crystals, or photonic quasicrystals, and they are the optical analogue of semiconducting materials. Whereas a semiconductor's band structure arises from the interaction of electron or hole waves with an arrangement of ion cores, the photonic crystal band structure results from the interaction of light waves with an arrangement of regions of differing refractive index. What makes photonic crystals highly attractive to the optical engineer is that we can actually place the regions of differing refractive index in a pattern specifically tailored to produce a given optical function, such as an extremely high dispersion, for example. That is, we can define the geometrical arrangement of the dielectric foam to provide us with the form of band structure we require for our optical functionality. In this paper, the optical properties and applications of these highly engineered mesoporous dielectrics will be discussed.
Topics: Chemical Engineering; Equipment Design; Equipment Failure Analysis; Models, Chemical; Models, Molecular; Molecular Conformation; Nanostructures; Optics and Photonics; Photochemistry; Polymers; Porosity
PubMed: 18272460
DOI: 10.1098/rsta.2005.1693 -
Journal of Nanoscience and... 2004A comprehensive understanding of the design, synthesis, characterization, and properties of boron carbonitride nanotubes (BCN) is presented in this review. Distinctive... (Review)
Review
A comprehensive understanding of the design, synthesis, characterization, and properties of boron carbonitride nanotubes (BCN) is presented in this review. Distinctive structural and electronic properties are revealed in theoretical studies of the BCN nanotubes and compared with the properties of carbon nanotubes. In the experimental studies, BCN nanotubes have been synthesized by various techniques. For different purposes, controllable growth processes have been used to fabricate BCN nanotubes with novel structures, such as nanojunctions and filled nanotubes. Some interesting phenomena originating from the substitution of B and N atoms, such as the phase segregation, are considered theoretically and experimentally. Mainly the physical properties--field electron emission and photoluminescence--are discussed, which turn out to have potential applications in the industry.
Topics: Boron Compounds; Crystallization; Electric Conductivity; Electrochemistry; Electromagnetic Fields; Luminescence; Materials Testing; Microscopy, Electron, Scanning; Molecular Conformation; Nanotechnology; Nanotubes; Photochemistry; Surface Properties
PubMed: 15112540
DOI: 10.1166/jnn.2004.018 -
Antioxidants & Redox Signaling Mar 2011The design, synthesis, and operation of molecular-scale systems that exhibit controllable motions of their component parts is a topic of great interest in nanoscience... (Review)
Review
The design, synthesis, and operation of molecular-scale systems that exhibit controllable motions of their component parts is a topic of great interest in nanoscience and a fascinating challenge of nanotechnology. The development of this kind of species constitutes the premise to the construction of molecular machines and motors, which in a not-too-distant future could find applications in fields such as materials science, information technology, energy conversion, diagnostics, and medicine. In the past 25 years the development of supramolecular chemistry has enabled the construction of an interesting variety of artificial molecular machines. These devices operate via electronic and molecular rearrangements and, like the macroscopic counterparts, they need energy to work as well as signals to communicate with the operator. Here we outline the design principles at the basis of redox switching of molecular motion in artificial nanodevices. Redox processes, chemically, electrically, or photochemically induced, can indeed supply the energy to bring about molecular motions. Moreover, in the case of electrically and photochemically induced processes, electrochemical and photochemical techniques can be used to read the state of the system, and thus to control and monitor the operation of the device. Some selected examples are also reported to describe the most representative achievements in this research area.
Topics: Electrochemistry; Nanotechnology; Oxidation-Reduction; Photochemistry
PubMed: 20568952
DOI: 10.1089/ars.2010.3223