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Structure, Reactivity, Nonlinear Optical Properties and Vibrational Study of 5-Thioxo-1,4-thiazaolidin-3-one and 5-thioxo-1,4,2-thiazasilolidin-3-one (Silicon vs. Carbon). A DFT Study
摘要： The structures and nonlinear optical properties (NLO) of 5-thioxo-1,4-thiazaolidin-3-one(Rhodanine) and 5-thioxo-1,4,2-thiazasilolidin-3-one (silarhodanine) tautomers were studied in gas phase and in solutions using the B3LYP density functional theory and composite CBS-QB3 method. The global minimum at the B3LYP/6-31++G(d,p) and CBS-QB3 levels of theory is tautomer 5 in the gas phase and in solvents for rhodanine, and simiarly, tautomer 13 is the global minimum for silarhodanine. The interconversion among the tautomers is proceeded by an intramolecular proton transfer reaction. An identical solvent effects can be noted for rhodanine and silarhodanine tautomers. The activation barrier towards ring-opening processes (1→2, 9→10) decreases with the increasing dielectric constant of the solvent; on the other hand, the barrier of the ring-closure processes (2→3, 10→11) increases with the increasing dielectric constant. The tautomers are predicted to show significant NLO properties. Also, a number of correlations between the dipole moment and electron densities in bond critical points of the S3-C4 bond and interaction energy as well as vibrational frequencies at the transition states (TS2–3,TS10–11) were examined under different solvents. Finally, the investigation of the heavy atom substitution effects on the properties of silarhodanine is proven to be very weak under these conditions.
关键词： Vibrational assignments,Silarhodanine,Reactivity,Rhodanine,NLO,Ring-opening,Solvent effects
更新于2025-09-23 15:23:52
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Photostable coumarin containing azo dyes with multifunctional property
摘要： A series five coumarin azo disperse dyes with thiophene bridge are synthesized using diazotized aniline derivatives which are confirmed by FT-IR, 1H NMR, 13C NMR, and CHN analysis. The dyes are applied on polyester and nylon material. The multifunctional properties (lightfastness, washing fastness, sublimation fastness, K/S, UPF, and antimicrobial activity) of the dyed fabric are determined. The dye 3a (-NO2) show red shifted absorption (649 nm) and blocking 95.5-97.4% of UV radiations with 96% antimicrobial property. The geometries of all the azo dyes are optimized using Density Functional Theory (DFT). The Global Reactivity Descriptors (GRD) are evaluated at the same method of theory. The GRD obtained shows a linear relation with lightfastness and UPF ratings. The antimicrobial activity of all synthesized dyes are determined by AATCC 100 test method and it is correlated with the HOMO-LUMO energy band gap.
关键词： UPF,fastness property,Coumarin-azo dyes,global reactivity descriptors,HOMO-LUMO gap,antimicrobial activity
更新于2025-09-23 15:23:52
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Rapid Quantitative Analysis of Forest Biomass Using Fourier Transform Infrared Spectroscopy and Partial Least Squares Regression
摘要： Fourier transform infrared reflectance (FTIR) spectroscopy has been used to predict properties of forest logging residue, a very heterogeneous feedstock material. Properties studied included the chemical composition, thermal reactivity, and energy content. The ability to rapidly determine these properties is vital in the optimization of conversion technologies for the successful commercialization of biobased products. Partial least squares regression of first derivative treated FTIR spectra had good correlations with the conventionally measured properties. For the chemical composition, constructed models generally did a better job of predicting the extractives and lignin content than the carbohydrates. In predicting the thermochemical properties, models for volatile matter and fixed carbon performed very well (i.e., R2 > 0.80, RPD > 2.0). The effect of reducing the wavenumber range to the fingerprint region for PLS modeling and the relationship between the chemical composition and higher heating value of logging residue were also explored. This study is new and different in that it is the first to use FTIR spectroscopy to quantitatively analyze forest logging residue, an abundant resource that can be used as a feedstock in the emerging low carbon economy. Furthermore, it provides a complete and systematic characterization of this heterogeneous raw material.
关键词： FTIR spectroscopy,forest logging residue,energy content,partial least squares regression,thermal reactivity,chemical composition
更新于2025-09-23 15:22:29
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Chemistry and Structure of Silver Molecular Nanoparticles
摘要： Silver and gold molecular nanoparticles (mNPs) are a relatively new class of interest. They are high-nuclearity metal?organic molecular materials of compounds, with ligated metal cores, where the different character of bonding in the ligand shell and metal core gives rise to many of the unique properties of these materials. Research has primarily focused on gold mNPs, due to their good stability and the ease with which they may be synthesized and processed. To understand these materials as a general class, however, it will be necessary to broaden research efforts to other metals. Gold and silver are isoelectronic and have the same atomic radius, making the comparison of gold and silver mNPs attractive. The optical and chemical differences of the two metals provide useful contrasts, however, as well as a means to access a wider range of properties.
关键词： gold molecular nanoparticles,reactivity,structure,synthesis,silver molecular nanoparticles
更新于2025-09-23 15:21:21
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<p>Assessing Renal Microvascular Reactivity by Laser Speckle-Contrast Imaging in Angiotensin-II-Treated Mice</p>
摘要： The kidney is one of the main organs affected by microvascular damage wrought by hypertension. We developed an approach to investigate renal microcirculatory disturbance in live mice by measuring post-occlusive reactive hyperemia (PORH), a reactivity test exploring endothelial and neuro-microvascular functioning. Laser speckle-contrast analysis (LASCA) assesses microvascular blood flow; it provides real-time images of spatial and temporal blood flow dynamics. We compared basal blood flow and PORH test between control and angiotensin-II-treated mice (Ang-II) to validate the model.
关键词： hypertension,renal microcirculation,laser speckle-contrast analysis,microvascular reactivity
更新于2025-09-23 15:21:01
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BOLD-based cerebrovascular reactivity vascular transfer function isolates amplitude and timing responses to better characterize cerebral small vessel disease
摘要： Cerebrovascular reactivity (CVR) is a dynamic measure of the cerebral blood vessel response to vasoactive stimulus. Conventional CVR measures amplitude changes in the blood‐oxygenation‐level‐dependent (BOLD) signal per unit change in end‐tidal CO2 (PETCO2), effectively discarding potential timing information. This study proposes a deconvolution procedure to characterize CVR responses based on a vascular transfer function (VTF) that separates amplitude and timing CVR effects. We implemented the CVR‐VTF to primarily evaluate normal‐appearing white matter (WM) responses in those with a range of small vessel disease. Comparisons between simulations of PETCO2 input models revealed that boxcar and ramp hypercapnia paradigms had the lowest relative deconvolution error. We used a T2* BOLD‐MRI sequence on a 3 T MRI scanner, with a boxcar delivery model of CO2, to test the CVR‐VTF approach in 18 healthy adults and three white matter hyperintensity (WMH) groups: 20 adults with moderate WMH, 12 adults with severe WMH, and 10 adults with genetic WMH (CADASIL). A subset of participants performed a second CVR session at a one‐year follow‐up. Conventional CVR, area under the curve of VTF (VTF‐AUC), and VTF time‐to‐peak (VTF‐TTP) were assessed in WM and grey matter (GM) at baseline and one‐year follow‐up. WMH groups had lower WM VTF‐AUC compared with the healthy group (p < 0.0001), whereas GM CVR did not differ between groups (p > 0.1). WM VTF‐TTP of the healthy group was less than that in the moderate WMH group (p = 0.016). Baseline VTF‐AUC was lower than follow‐up VTF‐AUC in WM (p = 0.013) and GM (p = 0.026). The intraclass correlation for VTF‐AUC in WM was 0.39 and coefficient of repeatability was 0.08 [%BOLD/mm Hg]. This study assessed CVR timing and amplitude information without applying model assumptions to the CVR response; this approach may be useful in the development of robust clinical biomarkers of CSVD.
关键词： cerebral small vessel disease,BOLD,cerebrovascular reactivity,white matter hyperintensities,fMRI
更新于2025-09-19 17:15:36
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Optic Nerve Head Astrocytes Display Axon-Dependent and -Independent Reactivity in Response to Acutely Elevated Intraocular Pressure
摘要： PURPOSE. Optic nerve head (ONH) astrocytes provide support for axons, but exhibit structural and functional changes (termed reactivity) in a number of glaucoma models. The purpose of this study was to determine if ONH astrocyte structural reactivity is axon-dependent. METHODS. Using rats, we combine retrobulbar optic nerve transection (ONT) with acute controlled elevation of intraocular pressure (CEI), to induce total optic nerve axon loss and ONH astrocyte reactivity, respectively. Animals were euthanized immediately or 1 day post CEI, in the presence or absence of ONT. ONH sections were labeled with fluorescent-tagged phalloidin and antibodies against b3 tubulin, phosphorylated cortactin, phosphorylated paxillin, or complement C3. ONH label intensities were quantified after confocal microscopy. Retrobulbar nerves were assessed for axon injury by light microscopy. RESULTS. While ONT alone had no effect on ONH astrocyte structural orientation, astrocytes demonstrated significant reorganization of cellular extensions within hours after CEI, even when combined with ONT. However, ONH astrocytes displayed differential intensities of actin (phosphorylated cortactin) and focal adhesion (phosphorylated paxillin) mediators in response to CEI alone, ONT alone, or the combination of CEI and ONT. Lastly, label intensities of complement C3 within the ONH were unchanged in eyes subjected to CEI alone, ONT alone, or the combination of CEI and ONT, relative to controls. CONCLUSIONS. Early ONH astrocyte structural reactivity to elevated IOP is multifaceted, displaying both axon dependent and independent responses. These findings have important implications for pursuing astrocytes as diagnostic and therapeutic targets in neurodegenerative disorders with fluctuating levels of axon injury.
关键词： elevated intraocular pressure,glaucoma,optic nerve head,axon,astrocyte reactivity
更新于2025-09-19 17:15:36
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Time-resolved laser-flash photolysis Faraday rotation spectrometer: a new tool for total OH reactivity measurement and free radical kinetics research
摘要： The total OH reactivity (k’OH) is an important parameter for quantitative assessment of the atmospheric oxidation capacity. Although laboratory measurement of k’OH has been achieved 20 years ago, the instruments required are often costly and complex. Long-term atmospheric observations remain challenging and elusive. In this work, a novel instrument combining laser-flash photolysis with a mid-infrared Faraday rotation spectrometer (LFP-FRS) has been developed for the measurement of k’OH and for studying gas phase free radical kinetics. The reactor is composed of a Herriott-type optical multipass cell, and OH radicals were generated by flash photolysis of ozone with a 266 nm pulsed Nd:YAG laser. The decay of the OH signal was directly measured with a time-resolved FRS spectrometer at 2.8 μm. The overlapping pathlength between the pump beam and probe beam was 25 m. High performance was achieved by subtracting the signals before and after flash photolysis to eliminate interferences caused by H2O absorption and background drift. The optimum precisions (1σ) of OH concentration and k’OH measurement were 4×106 molecule cm-3 and 0.09 s-1 over data acquisition times of 56 s and 112 s, respectively. The performance of the system was evaluated by the reaction of OH with CO and NO. The measured rate coefficients (kOH+CO and kOH+NO) were in good agreement with values reported in the literature. The developed LFP-FRS provides a new, high precision, and highly selective tool for atmospheric chemistry research of OH radicals and other transient paramagnetic free radicals such as HO2 radicals.
关键词： atmospheric oxidation capacity,total OH reactivity,laser-flash photolysis,free radical kinetics,Faraday rotation spectrometer
更新于2025-09-19 17:13:59
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Impact of Plasmonic Photothermal Effects on the Reactivity of Au Nanoparticle Modified Graphene Electrodes Visualized Using Scanning Electrochemical Microscopy
摘要： Atomically-thin graphene electrodes enable the modulation of interfacial reactivity by means of underlying substrate effects. Here we show that plasmonic excitation of microscopic arrays composed of 50 nm Au nanoparticles situated underneath a graphene interface results in localized enhancements on the electrochemical readout. We used scanning electrochemical microscopy (SECM) in the feedback and H2O2 collection modes to identify the role of the generated plasmons on the electrochemical response. Using electrochemical imaging, supported by finite-element method simulations, we confirmed that a temperature rise of up to ~30 K was responsible for current enhancements observed for mass transfer-limited reactions. On single-layer graphene (SLG) we observed a shift in the onset of H2O2 generation which we traced back to photothermal induced kinetic changes, raising ko’ from 1.1 x 10-8 m/s to 2.2 x 10-7 m/s. Thicker 10-layer graphene electrodes displayed only a small kinetic difference with respect to SLG, suggesting that photothermal processes, in contrast to hot carriers, are the main contributor to the observed changes in interfacial reactivity upon illumination. SECM is demonstrated to be a powerful technique for elucidating thermal contributions to reactive enhancements, and presents a convenient platform for studying temperature-dependent phenomena over individual sites on electrodes.
关键词： scanning electrochemical microscopy,graphene electrodes,plasmonic photothermal effects,Au nanoparticle,electrochemical reactivity
更新于2025-09-19 17:13:59
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Preparation and Characterization of Water-soluble ZnSe: Fe/ZnSe Quantum Dots
摘要： A chiral phosphoric acid-catalyzed kinetic resolution and desymmetrization of para-quinols operating via oxa-Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s-factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide insights to previously reported chiral anion phase transfer reactions involving chiral phosphate catalysts in combination with boronic acids.
关键词： directed reactivity,oxa-Michael addition,kinetics,asymmetric catalysis,chiral phosphoric acid,reaction mechanisms
更新于2025-09-11 14:15:04