Laser Photochemistry Research Articles

Cellulose‐Derived Wearable Carbon Nanoflake Sensors Customized by Semiconductor Laser Photochemistry

AbstractMulti‐functional wearable electrical materials have been regarded as one of the most pivotal cornerstones for the booming internet of things (IoTs), biomimetic robotics/science, and sensory e‐skins. Nevertheless, customizable, high‐throughput, batch‐fabricated, function‐integrated wearable electronics remain technologically challenging to traditional material engineering. Hereby, a cellulose‐converted active amorphous carbon nanomaterial is developed via a transfer‐free, precursor‐free rapid laser synthesis method incorporating deformation‐tolerant waste papers. The lattice fringe spacing of laser‐synthesized carbon nanoflake is ≈0.305 nm topologically distinct from graphene or carbon dots. The nanostructured three‐dimensional (3D) carbon network exhibits desirable mechanical flexibility, high hygroscopicity/electrical conductivity, large ion storing capacity for Zn2+ or Na+, high sensitivity to pressure, and a natural microwave absorbing ratio (> 37 dB at the terahertz range). Abundant percolation pathways inside cellulose/carbon composite networks offered fast electrolyte diffusion and carrier mobility. A series of low‐cost highly‐deformable interdigitated supercapacitors, tactile sensors, electrical circuits, and functional coatings are experimentally fabricated and identified, enabling waste paper as a function‐magnified meta platform for e‐skins, wearable energy devices, or IoTs interfaces.

Visible light photochemical synthesis of ultrasmall palladium/copper bimetallic particles at room temperature and its catalytic application in degradation of p-NP

Pt-based metals are very effective catalysts widely adopted in many fields. But the high cost prevents its further industrial application. One of the effective ways to solve the problem is to replace platinum with relatively cheap palladium and its alloy with copper. However, producing Pd/Cu bimetallic catalysts efficiently and economically with controllable particle size and uniform distribution is still challenging, especially when trying to reduce the consumption of precious metals. In this paper, ultrasmall palladium/copper (Pd/Cu) bimetallic catalysts with even dispersion were prepared on multi-walled carbon nanotubes (MWCNTs) by adding polyethylene glycol 400 (PEG 400) as a reducing agent and stabilizer under visible light irradiation at room temperature. The catalytic performance was studied in the catalysis of p-nitrophenol (p-NP) reduction. Of all the bimetallic catalysts produced in different conditions, the best one was obtained under the reaction condition of pH = 7 and violet light irradiation (wavelength 380–435 nm). The average particle size of 0.85 nm, and the apparent rate constant in the catalysis is 1.47 min−1. This research probes the role of visible light as a key kinetic controlling method in the formation of ultrasmall particles (UPs). It proves the effectiveness of using visible light irradiation as an effective and more “green chemistry” approach to get precious metal UPs as catalysts beyond the traditional ultraviolet or laser photochemistry methods.

Photochemical Synthesis and Spectroscopy of Covalent PAH Dimers.

Laser photochemistry of pressed-pellet samples of polycyclic aromatic hydrocarbons (PAHs) produces covalently bonded dimers and some higher polymers. This chemistry was discovered initially via laser desorption time-of-flight mass spectrometry experiments, which produced masses (m/z) of 2M-2 and 2M-4 (where M is the monomer parent mass). Dimers are believed to be formed from photochemical dehydrogenation and radical polymerization chemistry in the desorption plume. Replication of these ablation conditions at higher throughput allowed PAH dimers of pyrene, perylene, and coronene to be produced and collected in milligram quantities. Differential sublimation provided purification of the dimers and elimination of residual monomers. The purified dimers were investigated with UV-visible, IR, and Raman spectroscopy, complemented by computational studies using density functional theory at the CAM-B3LYP/def2-TZV level. Calculations and predicted spectra were calibrated by comparison with the corresponding monomers and used to determine the lowest energy dimer structures. Infrared and Raman spectroscopy provided few distinctive signatures, but UV-visible spectra detected new transitions for each dimer. The comparison of simulated and experimental spectra allows determination of the most prevalent structures for the PAH dimers. The work presented here provides interesting insights into the spectroscopy of extended aromatic systems and a new strategy for the photochemical synthesis of large PAH dimers.

Kinetic Measurements of Singlet Oxygen Phosphorescence in Hydrogen-Free Solvents by Time-Resolved Photon Counting.

Solvents lacking hydrogen atoms are very convenient models for elucidating the properties of singlet oxygen, since the lifetime of singlet oxygen in these solvents reaches tens milliseconds. Measuring intrinsic infrared (IR) phosphorescence of singlet oxygen at 1270 nm is the most reliable method of singlet oxygen detection. However, efficient application of the phosphorescence method to these models requires an equipment allowing reliable measurement of the phosphorescence kinetic parameters in the millisecond time range at low rates of singlet oxygen generation, which is a technically difficult problem. Here, we describe a highly sensitive LED (laser) spectrometer recently constructed in our laboratory for the steady-state and time-resolved measurements of the millisecond phosphorescence of singlet oxygen. In the steady-state mode, this spectrometer allows detection of singlet oxygen phosphorescence upon direct excitation of oxygen molecules in the region of dark-red absorption bands at 690 and 765 nm. For kinetic measurements, we used phenalenone as a photosensitizer, microsecond pulses of violet (405 nm) LED for excitation (irradiance intensity, ≤50 μW/cm2), a photomultiplier and a computer multichannel scaler for time-resolved photon counting. The decays of singlet oxygen in air-saturated CCl4, C6F6, and Freon 113 and quenching of singlet oxygen by phenalenone and dissolved molecules of triplet oxygen were measured. The relative values of the radiative rate constants of singlet oxygen in these media were determined. The results were compared with the absorption coefficients of oxygen measured by our group using the methods of laser photochemistry. Critical discussion of the obtained results and the data of other researchers is presented.

Laser photochemistry of oxygen. Application to studies of the absorption spectra of dissolved oxygen molecules

This paper summarizes the data of our lab on the rates of photooxygenation of singlet oxygen traps upon direct laser excitation of oxygen in air-saturated organic solvents and water. Methods of application of these data to calculation of absorbance ( A ) and molar absorption coefficients ( e ) in the maxima of the main oxygen absorption bands (1273, 765 and 1070 nm) are discussed. The most accurate results were obtained from comparing the photooxygenation rates upon porphyrin-photosensitized and direct excitation of oxygen molecules. It is shown that e 1273 is not sensitive to the presence of heavy atom (bromine) in solvent molecules and markedly decreases on going from non-polar solvents to water being proportional to the radiative rate constants obtained from the quantum yields of singlet oxygen phosphorescence at 1274 nm. The coefficient e 765 markedly increases in the presence of bromine. In solvents lacking heavy atoms the 1.5-2-fold increase of e 765 was observed on going from non-polar solvents to water. Simultaneously, the ratios e 1273 / e 765 are changed from (7-10)/1 in non-polar solvents to 1.5/1 in water. The value of e 1070 obtained in carbon tetrachloride is shown to be about two orders smaller than e 1273 in the same solvent. The results are important for both analyses of oxygen photonics and dosimetry of laser radiation in biomedical experiments.

Spectroscopy of laser-induced autoionizing nonlinear resonances in atomic systems

Efficient harmonic generation at laser-induced autoionizing state in continuum, were observed for the first time by our laboratory [1,2,3]. In this paper, nonlinear frequency mixing in alkali metal vapors at induced continuum structure in Na, are studied in detail. Besides, measurement of nonlinear optical susceptibility at induced autoionizing resonance, is performed. Tunable ultraviolet radiations by four-photon processes near induced resonances are obtained. Estimations of the real and imaginary parts of the nonlinearities, are estimated. We will specially note, that the resonant photoabsorption of ions is experimentally investigated since it gives information about the autoionizing states, which is impossible to obtain on the base only of the emission spectra. We use also laser inducing for obtaining of powerful radiation source in VUV. Thus, many actual problems as the selective impact on matter, laser photochemistry and laser isotope separation are connected directly with the induced autoionizing nonlinear resonances. The main interest is to control the spectral characteristics of continuum. The discrete level from the continuum structure leads to appearance of asymmetrical autoionizing resonance onto the background of the broad-band absorption line.

Blue Luminescent Graphene Quantum Dots by Photochemical Stitching of Small Aromatic Molecules: Fluorescent Nanoprobes in Cellular Imaging

Blue fluorescent graphene quantum dots (GQDs) are synthesized from small haloaromatic molecules by laser photochemistry. The process involves a bottom-up photochemical stitching mechanism of the free radicals generated by irradiation of ultraviolet photons (λ = 248 nm) on o-dichlorobenzene. The GQDs are further demonstrated to be of importance as fluorescent nanoprobes in bioimaging of cells.

History of laser development on organic compounds (LOC): II. Photochemical laser is an important stage in LOC development

The development of photochemical lasers concepts around fast adiabatic photochemical reactions is considered. The first investigations connected with photochemical lasers based on the intra- and intermolecular proton-transfer reactions and attempts to obtain laser radiation of excimers and exciplexes of aromatic compounds have been analyzed. The dynamics of the process of formulating criteria to select active media for forecasting the radiation properties of prospective active media for photochemical lasers is outlined. The estimation of the photochemical laser as an instrument for broadening the spectral range of the laser radiation of organic compounds is given. The historical importance of photochemical lasers in the development of the investigations of lasers on organic compounds has been determined.

2SA-01 What should we learn from laser photochemistry of supramolecules? : Cooperative photochemical dynamics in biological systems?(2SA Photobiophysics promoted by young scientists,The 49th Annual Meeting of the Biophysical Society of Japan)

2SA-01 What should we learn from laser photochemistry of supramolecules? : Cooperative photochemical dynamics in biological systems?(2SA Photobiophysics promoted by young scientists,The 49th Annual Meeting of the Biophysical Society of Japan)

ChemInform Abstract: Space- and Time-Resolved Laser Spectroscopy and Photochemistry of Organic Solids

Abstract In inhomogeneous organic solid systems it is indispensable to measure photoprimary processes as a function of position and to elucidate photochemical processes. For this purpose some space- and time-resolved spectroscopic methods have been developed. Total internal reflection fluorescence spectroscopy makes it possible to obtain a concentration profile or fluorescent species from the surface/interface to the bulk and to discriminate the dynamics of the surface/interface layers from that of the bulk. Laser photolysis, which involves monitoring the transient species under multiple-reflection conditions, gives dynamic information on thin films of submicron thickness. As an example, the diffusion coefficient of holes in a photoconductive film has been estimated by analysing the absorption decay of photo-induced charge carriers. By a combination of time-correlated single-photon counting with a confocal laser-scanning microscope, three-dimensionally submicrometre space-resolved and picosecond time-resolved fluorescence measurements can be made. This has also been extended to transient absorption spectroscopy. To study the photochemistry of organic solid particles, a laser manipulation method utilizing laser-trapping phenomena has been introduced and combined with microscope spectroscopy. One can choose a single particle in the dispersed solution, characterize it, induce chemical reactions on it and fabricate it. These recent advances in space- and time-resolved spectroscopy and its high potential in organic solids photochemistry are summarized and new trends in photochemistry are discussed.

The Clausius inequality: Implications for non-equilibrium thermodynamic steady states with NEMD corroboration

The Clausius inequality for closed systems was deduced from the Riemann integration of closed Carnot cycle loops for irreversible transitions. The corresponding inequalities for open system Carnot cycles are derived here. Their properties indicate that no new non-equilibrium entropy is evident as has been proposed over the decades. It is proven that a sequence of points along a non-equilibrium state space must have excess variables augmenting those for the equilibrium situation and therefore the principle of local equilibrium (PLE) used extensively to describe non-equilibrium systems is an approximation. To demonstrate the breakdown of the principle, verification of the theorem, and the presence of new phenomena, an ab initio steady-state simulation of a simple dimer reaction 2 A ↔ A 2 under non-equilibrium conditions was performed and the results compared to the equilibrium conditions to show the regime of breakdown of the principle. The novel dimer reaction presented has a cyclical pathway found in many natural processes, such as laser photochemistry. It is suggested that such reaction pathways can exist and awaits experimental verification. A new algorithm to conserve momentum and energy at the potential switches of the dimer is applied effectively. New atomic and molecular flux flows not present under equilibrium conditions are shown to exist, where the net rate of reaction along the cell is not zero but small, unlike the zero rate equilibrium requirement, leading to the flux presence. The equilibrium constant is also shifted from the value at thermodynamical equilibrium. Unless reinterpreted differently, it is shown that the so-called Curie symmetry principle, fundamental in deciding on the feasibility of flux–force couplings in both theory and experiment in all physical theories, cannot apply to such experimental results. Hence, a far greater freedom in selecting appropriate force–flux couplings is indicated than would be the case if the Curie principle, as commonly interpreted is adopted.

A Review of Laser Technology and Light-Tissue Interactions as a Background to Therapeutic Applications of Low Intensity Lasers and Other Light Sources

This paper reviews aspects of laser physics, radiometry and photochemistry relevant to the use of low intensity light therapy delivered by lasers or conventional lamps. Current theories regarding the biophysical mechanisms of low intensity laser therapy are reviewed. Characteristics of laser radiation such as monochromaticity, coherence, collimation, speckle, beam profile, penetration depth and temporal modulation of irradiation, and the relevance of these factors to photon propagation are explained. Physical principles that describe light–tissue interactions are presented. The importance of irradiance and radiant exposure is discussed and methods of quantifying these values are shown. Clinical implications are briefly discussed.

The 254 nm low intensity and 266 nm laser photochemistry of adenosine.: Effect of pH and concentration on the reactive precursors of the principal products, adenine and FAPyAde

The 254 nm low intensity steady-state photolysis of adenosine in aqueous solutions at different pHs and concentrations was studied. The quantum yield of photodestruction of adenosine decreases as the pH is increased: (1.7±0.1)×10 −2 (pH 2.6), (1.20±0.04)×10 −2 (pH 6.5) and (0.29±0.01)×10 −2 (pH 13.3). For the photodestruction of adenosine and the formation of adenine the quantum yield depends on the initial ground-state concentrations of adenosine and converges to a limiting value of the order of 10 −3 and 10 −4, respectively. The effect of different substrates that react selectively with postulated reactive intermediates of adenosine was studied and the short-lived precursors for the formation of the major products are proposed. For adenine and 4,6-diamino-5-formamidopyrimidine, two of the products formed with the highest yields, their quantum yield of formation were determined under different experimental conditions. Contributions from electron adducts of the base play a major role in N-glycosidic bond cleavage for the nucleoside. Increases in pH and concentration result in a decrease in the yield of formation of adenine. The dependence on pH and the electron scavenger experiments provide further evidence for the radical anion or its protonated form to be one of the principal species involved in the process of base release at neutral pH. At an acidic pH a tautomer of the radical cation of adenosine is proposed as the precursor for adenine formation. The relative efficiency of the radical cation of adenosine for initiating the release of adenine at neutral pH is intrinsically low (35–43%) and this correlates with the efficiency reported for other adenine-containing polymers. Furthermore, the photoionization of adenosine using a 266 nm nanosecond laser excitation occurs through a combination of one- and two-photon processes under the experimental conditions used. Reactions of OH radicals and oxygen reactive species may also result in base release as shown in irradiations done in the presence of N 2O and O 2 as additives. For 4,6-diamino-5-formamidopyrimidine, the addition N 2O does not affect its yield, implying that the hydroxyl radicals are not involved in its formation. However, the presence of O 2, Tl +, Ag +, OH −, H + or alcohols inhibits its formation.

Nanosecond and Femtosecond Laser Photochemistry and Ablation Dynamics of Neat Liquid Benzenes

Molecular mechanisms of nanosecond and femtosecond laser ablation and morphology-changing dynamics of neat liquid benzene derivatives, such as benzyl chloride and toluene, were investigated by photoacoustic measurement, nanosecond shadowgraphy, femtosecond surface light scattering imaging, and time-resolved ultraviolet−visible absorption spectroscopy. Ablation thresholds of the liquids were determined by photoacoustic measurement and shadowgraphy, whereas primary processes in ablation were elucidated by time-resolved absorption spectroscopy. Femtosecond surface light scattering imaging revealed how electronic excited/radical states evolved to nanometer morphological changes. In nanosecond laser ablation, ablation threshold value was related to photochemical reactivity producing benzyl radical; however, no correlation between the threshold and boiling point was confirmed. Indeed, a benzyl radical absorption band was clearly observed. Moreover, benzyl radical concentration at the threshold was estimated qua...

Photodissociation of simple molecules in the gas phase.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotodissociation of Simple Molecules in the Gas PhaseHiroyasu SatoView Author Information Laser Photochemistry Research Group, Department of Chemistry for Materials, Faculty of Engineering, Mi'e University, 1515 Kamihamacho, Tsu 514-8507, Japan Cite this: Chem. Rev. 2001, 101, 9, 2687–2726Publication Date (Web):September 12, 2001Publication History Received31 May 2000Published online12 September 2001Published inissue 1 September 2001https://doi.org/10.1021/cr990403lCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1664Altmetric-Citations72LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (484 KB) Get e-AlertsSupporting Info (3)»Supporting Information Supporting Information SUBJECTS:Dissociation,Energy,Lasers,Molecules,Photodissociation Get e-Alerts

The Structure of [Fe(CO)4 ]-An Important New Chapter in a Long-Running Story.

The structure of the singlet state (1 A1 ) of [Fe(CO)4 ] in the gas phase has been determined by a combination of laser photochemistry of [Fe(CO)5 ] and electron diffraction imaging. The ground state of [Fe(CO)4 ] is known to be a triplet species (3 B2 ), and this is the species detected in picosecond time-resolved IR experiments with [Fe(CO)5 ] in solution. This is an appropriate moment to survey the state of knowledge on [Fe(CO)4 ], beginning from the first low-temperature matrix experiments.

ChemInform Abstract: Laser Photochemistry of Molecular Oxygen

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Laser photochemistry of molecular oxygen.

Molecular oxygen poses very difficult challenges in molecular photochemistry due to the extreme weakness of its ultraviolet absorption spectrum. In the past few years a new technique called velocity map imaging has been able to overcome many of the experimental obstacles to the study of this all-important atmospheric species. In this Account several aspects of laser photochemistry of O(2) will be described, including the unraveling of the Herzberg and Schumann-Runge continua using velocity map imaging.

Laser-induced photodecomposition of amino acids and peptides: extrapolation to corneal collagen

Recent studies on the laser photochemistry of aromatic and aliphatic amino acids and small peptides in neutral aqueous solution are described. We report on major parameters such as photoionization and photodecomposition quantum yields for the cases of direct (and indirect) photolysis. Although four different UV laser sources were used, the impact is made on 193-nm-induced photoprocesses. The relative probabilities of photochemical damage of specific residues are estimated. It is shown that the peptide bond is likely to be the main target in collagen. Its scission could be the most important photochemical reaction taking place at 193-nm laser irradiation of the cornea. We have found strong arguments in favor of the ablative photodecomposition mechanism of photorefractive keratectomy.

Study of cluster materials obtained by selective laser photochemistry

This paper presents experimental results from the study of the characteristics of cluster materials obtained by resonance laser photochemistry. The effect of the redox reagents used in the photoprocessing on the size and shape of cluster structures of gold has been studied. The minimum size of the structures, measured by electron microscopy, is 30–50 nm. When organic acids are used as redox reagents, fractal structures formed from flat scales are synthesized. Redox reagents based on alcohols form cluster structures of fractal type consisting of spherical clusters.