Symmetric Vibrations Research Articles

Emerging NO2 gas sensing on substitutionally doped Fe on NiWO4 SCES insulators

In this study, we demonstrate the emergence of NO2 gas sensing capabilities in the typically non-active NiWO4, a strongly correlated electron system (SCES), by introducing substitutional Fe at the Ni site. NiWO4 typically exhibits strong Coulombic repulsion between Ni atoms, resulting in a large band gap of over 3.0 eV and insulating behavior. This correlated behavior is clearly reflected in the significant increase of band gap when considering the Hubbard U correction for the cations, bringing the theoretical value closer to the observed value. The single-phase Fe0.5Ni0.5WO4 displays a notable shift in the [NiO6] symmetric vibration mode and an increase in magnetization. Additionally, theoretical calculations confirm the preservation of the wide band gap, with the Fe and O levels generated within the band gap. These findings indicate that Fe located in the Ni sites modulate Coulombic repulsion in NiWO4 SCES insulators. Unlike the poor gas-sensing performance of intrinsic NiWO4, Fe0.5Ni0.5WO4 exhibits a significant NO2 response (Rg/Ra) of 11 at 200°C than other gases and a limit of detection (LOD) of 46.4 ppb. This study provides a pathway for realizing gas-sensing performance in strongly correlated electron insulators with large band gaps through the introduction of dopant levels at the cation sites.

Optimizing QLED Performance and Stability via the Surface Modification of PEDOT:PSS Experimental Insights and DFT Calculations.

The presence of the acidic and weak ionic conductor polystyrenesulfonate (PSS) in poly(3,4-ethylenedioxythiophene:PSS (PEDOT:PSS) leads to degradation and limits the charge transfer within quantum dot light-emitting diodes (QLEDs). Two-step solvent treatment resulted in a 40% reduction of PSS, which could be attributed to ethylene glycol (EG) attenuating the ionic interactions between PSS and PEDOT via interacting with PSS through hydrogen bonding. Methanol dissolved the predominant PSS and EG from the surface. The redshift of the peak representing the symmetrical vibration of Cα═Cβ in the Raman spectrum confirmed the conformation of benzoid structure to quinoid structure after the surface treatment. This conformation was attributed to the extension of the conjugation length and the reduction of the energy barrier within the PEDOT chain. This resulted in the improved conductivity and charge hopping of the PEDOT:PSS, which was also proven using density functional theory (DFT) calculations. Reducing the insulating and acidic PSS improved the electroluminescence performance and extended the operational lifetime of the QLEDs. The tris(dimethylamino)phosphine-based InP QLEDs exhibited an external quantum efficiency (EQE) of 6.4%, that value is comparable to those of tris(trimethylsilyl)phosphine-based QLEDs, and operational lifetime (T50) of 125.6 h.

Sensitivity of the C–H Stretching Band in Raman Spectra to Phospholipid Order

ABSTRACTPhospholipid bilayers, which are a major component of cellular membranes and some drug delivery vehicles, can be in different states of order depending on the conformations of the hydrocarbon tails and their mutual arrangement. The important task of experimental characterization of phospholipid order is often addressed using Raman spectra of the C–H stretching bands. Such characterization uses some empirical relationships for apparent maxima in the spectra, although the origin of the sensitivity of the C–H band to phospholipid order and its model description remain unclear. Surely, a correct description of the sensitivity of the C–H band to phospholipid order is critical for its proper application. Here, we provide a description of the ordering sensitivity of the C–H stretching band using a polarized Raman experiment with hydrated aligned multibilayers of a saturated phospholipid. By this way, Raman contributions from symmetric and antisymmetric vibrations of CH2 were obtained in a model‐free manner. Experiments in a wide temperature range and the use of isotopic isolation helped us to consider separately the effects of conformational and lateral order of chains. The conformational sensitivity of the spectrum of antisymmetric vibrations was confirmed by DFT modeling. The outcomes of the study allowed us to provide recommendations for the use of the Raman spectrum of the C–H stretching band to characterize the conformational and lateral order of phospholipid‐containing materials.

An alternative approach in the synthesis of strontium-hydroxyapatite and strontium hydroxyapatite embedded in graphitic carbon nitride nanocomposites for potential tissue engineering applications

Sr-hydroxyapatite has drawn much attention with promising applications in biomedical engineering especially in drug delivery and tissue repair. A novel protocol for the preparation of Strontium hydroxyapatite (Sr-HAP) and Strontium hydroxyapatite encapsulated by graphitic carbon nitride (Sr-HAP@gCN) with high purity and better homogeneity was adopted for potential use in orthopaedic surgeries. The physiological pathway of Strontium and calcium inside humans follow the same trend leading to the mineral deposition of the bone. In the present study, a novel attempt in synthesizing Sr-HAP and Sr-HAP@gCN by the hydrothermal method is proposed for obtaining an ideal biomaterial with potential biocompatibility and pharmacological activity. Phase identification by X-ray diffraction (XRD), Fourier transform Infra-Red spectroscopic analysis (FTIR), Electron & atomic force microscopic studies, Thermogravimetric and Raman spectroscopic analysis was performed on the prepared Sr-HAP and Sr-HAP@gCN to characterize the incorporation efficiency of Strontium. Resazurin microtiter assay and MTT assay were used to evaluate antimicrobial susceptibility and biocompatibility. The typical crystal phase of Sr-HAP and a phase change in Sr-HAP@gCN have been demonstrated with special reference to the interfacial connection between gCN and Sr-HAP through FT-IR studies. Raman spectroscopy revealed the archetypal signature of symmetric and asymmetric PO vibrations pertaining to linearity change with the addition of Strontium. The biological effect of Sr-HAP and Sr-HAP@gCN was quite significant in inducing mineralization when kept immersed in simulated body fluid (SBF) for 21 days. Promising results pertaining to antimicrobial susceptibility and biocompatibility have been proved as an encouraging choice for drug delivery applications and bone filling applications.

Switched symmetric vibration SRS of −CxH2 by hydrogen bonding regulating conformations of aqueous NPA solution

Molecular conformation is an important characteristic feature of chemistry and physics, which exists in organic molecules. Based on the hydrogen bonding (HB) regulating conformations, we proposed a scheme to switch the stimulated Raman scattering peak from the symmetric vibration mode of −CαH2 (2878 cm−1) to that of −CβH2 (2937 cm−1) of n-propanol (NPA) aqueous solution with a volume fraction of 0.55. The dominant association structure can be converted from NPA–NPA to NPA–H2O by the HB network between H2O and NPA, and the HB structures were investigated through density functional theory calculations. The changes in intramolecular vibrational modes have effect on the relative abundances of NPA molecules by intermolecular HBs. This study can be extended to explore other organic molecular conformations in mixing solutions.

Symmetric and asymmetric vibration and buckling of a thermal rotating annular-plate with Pasternak foundation

This paper studies the symmetric and asymmetric vibration and buckling modes of a rotating thermal annular plate resting on a Pasternak foundation. With considering the von Kármán geometric nonlinearity and the first-order shear deformation theory, the governing equations of the system are established via Hamilton's principle, and then solved by using the differential quadrature method. With both inner and outer boundaries constrained, the modes of the rotating system vary differently depending on the mode symmetry. The symmetric modes are mainly affected by the generated centrifugal force, while the asymmetric ones are affected by both centrifugal and Coriolis forces. The additional Coriolis, with mainly two directions, strengthens the forward travelling parts of the asymmetric modes, but makes the backward counterparts buckled more easily. Also, the thermal effect, as well as boundary elasticity and foundation coefficients, are also investigated from the viewpoint of mode symmetry. Results show that the temperature rise can shift the fundamental vibration mode from the symmetric one to the asymmetric one and backward travelling waves for rotation, which also adds to the complexity of mode variation with joint parameters. For the joint effect of the temperature rise and rotating, the annular plate tends to buckle more readily while the effects of the two factors are linearly superimposed.

Wavelength-dependent photoisomerization of trans-4,4′-azopyridine: Nonadiabatic dynamics simulation

The trans–cis photoisomerization processes of 4,4′-azopyridine upon S1 and S2 excitations have been investigated by nonadiabatic dynamics simulations based on multi-reference CASSCF calculations. 119 sampling trajectories were simulated starting from the trans form excited to the S1 (S2) state and the cis-isomer quantum yield is evaluated to be (3 ± 2)% ((18 ± 4)%), which is qualitatively in agreement with the recent experimental results in ethanol. We found that rotation around the central N-N bond accompanied by the N-N-C symmetrical bending vibrations is the main mechanism in photoisomerization of the target molecule excited to the S1 and S2 states. Upon S1 excitation, S1-S0 transition occurs earlier along the C-N-N-C torsional coordinate, leading to a low cis-isomer quantum yield. Upon S2 excitation, half of the simulated trajectories are trapped in a potential well on the S2 state, from which the twisted conical intersections are more easily reached in the internal conversion, resulting in a higher cis-isomer quantum yield.

Preparation and drug delivery of hydrogels based on grafting of methacrylamide (MAAm) / vinylsulphonic acid (VSA) co monomers onto psyllium

Recently, a plethora of advancements have been made in the area of polysaccharide research to improve their properties for human health care. The present research is an attempt to develop hydrogels from through grafting of methacrylamide (MAAm) and vinyl sulphonic acid (VSA) co monomers onto psyllium for use in drug delivery (DD) applications. Copolymer hydrogels were characterized by scanning electron micrographs (SEM), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 13C nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA) and differential thermal analysis (DTG). SEM, AFM and XRD revealed heterogeneous morphology of the copolymer hydrogels with surface roughness and amorphous state of polymer chains in copolymer hydrogels due to graft-copolymerization reactions. The appearance of the FTIR bands at 1636.87 (amide-I), 1618.11 cm−1 (amide- II), 1469.58 cm−1 (amide- III) indicated presence of amide and bands at 1167.12 cm−1, 1112.06 cm−1 band (symmetric vibrations of SO3H groups and anti-symmetric & symmetric stretching modes of C–S) presence of VSA. The appearance of bands at 181.801 ppm and 62.053 ppm indicated presence of CO carbon of functional groups poly (MAAm) and −CH2–SO3H of poly (VSA) in copolymer hydrogels. Diffusion of the antibiotic drug vancomycin occurred in sustained manner with a non-Fickian diffusion mechanism. The release profile was best described by Korsmeyar-Peppas kinetic model. The copolymers exhibited biocompatible nature and revealed haemolytic index less than 5 % during polymer-blood interactions. The hydrogel demonstrated mucoadhesive character and required 0.135 ± 0.01 N force to detach from mucous membrane. These properties demonstrated the suitability of copolymer hydrogels for drug delivery applications.

Splitter-plate proximity-induced transitions in flow-induced vibration of a triangular prism

The effect of a splitter-plate downstream of an elastically mounted equilateral triangular prism on flow-induced vibration is numerically investigated at Reynolds number Re = 100, mass ratio m* = 10, damping ratio ζ = 0.005, cylinder-plate gap G* = 0.3, and various angle of attacks α = 0°–60°. The α = 0° and 60° correspond to vertex and edge of the cylinder facing the free stream. Under the effect of the splitter plate, a single transition from vortex-induced vibration (VIV) to proximity-induced galloping (PIG) in the vibrational response for an axisymmetric circular cylinder is reported, whereas, for the present non-axisymmetric triangular prisms, the varying α exhibits four proximity-induced transitions: VIV to modified VIV at smaller α = 0° and 25°, VIV to PIG at α = 35°, distinct VIV-galloping to combined PIG-galloping at α = 40°, and asymmetric to symmetric-galloping at larger α = 60°. The plate results in more symmetric vibration for high α ≥ 35°, while a reduction is observed for α ≤ 25°. The gap-flow leads to onset (α = 35°) and enhancement (α = 40°) of afterbody re-attachment on the prism, which significantly enhances the galloping instability and vibrational amplitude. A reduction in galloping instability leading to a slight reduction in amplitude is found for α = 60° prism. The study shows that the presence of the splitter-plate downstream influences near-wake structure and far-wake vortex shedding modes, which lead to stabilizing and destabilizing near-wake flow and distinct vibrational characteristics—depending on the angle of attack (α).

Effect of manganese (Mn) doping on the structural, dielectric, ferroelectric, and ferromagnetic properties of ceria (CeO2)

The Ce1-xMnxO2 ceramics were prepared using a solid-state route, with Mn doping concentrations of (x = 0.00, 0.03, 0.08, 0.13, and 0.18). Examination of X-ray diffraction patterns confirms the effective insertion of Mn into the CeO2 lattice, resulting in discernible changes in oxygen vacancy concentration and lattice expansion. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Ce3+, Ce4+, Mn3+, and Mn2+ oxidation states. The Photoluminescence (PL) spectra reveal the existence of oxygen vacancies, as manifested by the appearance of peaks within the energy range spanning from 3.1 eV to 2.71 eV. Raman spectra reveal a symmetric vibration around 466.81 cm-1 in all samples. The surface morphology of the samples exhibited subtle changes in grain size upon the introduction of Mn into CeO2. The dielectric behavior, investigated across a range of frequencies with varying Mn doping concentrations, exhibits an increased dielectric constant in Mn-doped CeO2, particularly with a smaller dielectric loss at lower frequencies. The ferroelectric response revealed a maximum recoverable energy density of 0.56 mJ/cm2 with an efficiency of 47.86% for CeO2. The room temperature magnetic response of the samples improved as Mn concentration increased, which is well explained by the Bound Magnetic Polarons (BMPs) and exchange interactions model. Overall, the studies show the effect of structural, electrical, and magnetic properties after doping with Mn, opening avenues for diverse applications of these ceramics.

Microwave dielectric properties, Raman spectra and sintering behavior of novel low loss La7Nb3W4O30 ceramics with rhombohedral structure

This study introduced a novel low-loss tungstate ceramic, La7Nb3W4O30 (LNWO), synthesized using the solid-state techniques. The structural analysis of the La7Nb3W4O30 ceramic material, utilizing X-ray diffraction (XRD) patterns and followed by detailed structural refinement, validated its rhombohedral structure. Transmission electron microscopy (TEM) was utilized to confirm the ordered layer arrangement characteristic of the rhombohedral structure. The internal structure was characterized by scanning electron microscopy (SEM), with the sample's relative density reaching 97.5 %. The correlation between the full width at half maximum (FWHM) of the Raman matrix at 901 cm−1 corresponding to the symmetric bending mode vibrations of WO5 and the Q × f value was discussed. Furthermore, the main factors affecting the dielectric constant, including density, bond valence, secondary phases, and variations in porosity, were analyzed. Encouragingly, the ceramic showed significant microwave dielectric properties when it was sintered at 1425 °C (εr = 23.68, Q × f = 26,687 GHz (f = 7.2 GHz), τf = −35.2 ppm/°C).

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal.

The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

INVESTIGATION OF SOLVATION IN LITHIUM PERCHLORATE -PROPYLENE CARBONATE-DIMETHYL CARBONATE SYSTEM BY RAMAN SPECTROSCOPY

The difference of solvent properties can significantly affect the solvation phenomena in individual and, especially, in mixed solutions. In particular, it can be assumed that in mixed solvents, i.e. in systems with intermediate dielectric permittivity (mixtures of linear and cyclic carbonic acid esters), cations will bind molecules of linear esters more strongly and bind molecules of cyclic esters more weakly than it takes place in individual solvents. In the present work the Raman spectra of lithium perchlorate solvents in propylene carbonate (PC), dimethyl carbonate (DMC) and their mixture in a wide range of salt concentrations are studied. It is shown that the solvation effects of the cation are clearly traced in the region of symmetric ring vibrations (~690-730 cm-1) of propylene carbonate and in the region of deformation vibrations of CCA (~520 cm-1) of dimethyl carbonate. These effects are also evident in the mixed solvent. The so-called method of differential spectroscopy was used to judge the structural changes of mixed-solvent systems. It consisted in constructing spectra of lithium salt solutions in mixed solvents, additive sum of spectra of lithium salt solutions in PC and DMC, as well as their difference (differential spectra). The analysis of differential spectra allows us to conclude that in systems with mixed solvent there is a weakening of interaction of propylene carbonate molecules with ions, and there is a preferential solvation of cations and anions by dimethyl carbonate molecules. Also, unlike propylene carbonate, dimethyl carbonate solvates perchlorate ions, which follows from the line contour changes in the region of CH3-group vibrations (2970 cm-1) solvation of anions is also observed in the mixed solvent. For citation: Rabadanov K.Sh., Gafurov M.M., Akhmedov M.A., Rabadanova D.I., Magomedova A.G. Investigation of solvation in lithium perchlorate -propylene carbonate-dimethyl carbonate system by raman spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 36-42. DOI: 10.6060/ivkkt.20246705.6967.

Chemically Synthesized Sb-Doped SnO2 Nanoparticles for Supercapacitor Application

This study explores the potential of antimony tin oxide (ATO) as an electrode material for supercapacitor applications. ATO, known for its exceptional electrical conductivity and stability, was synthesized using the coprecipitation method followed by calcination. The resulting ATO powder underwent thorough characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). XRD analysis confirmed the tetragonal morphology and phase purity of ATO nanoparticles, while SEM revealed a sphere-like structure with an irregular surface. FTIR spectroscopy identified various functional groups, including O–H stretching, C–H symmetric and asymmetric vibrations, and the characteristic–SnO2; vibration mode, providing insights into the surface properties crucial for electrochemical performance. Electrochemical evaluations, conducted through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, demonstrated a specific capacitance of 140 F/g for the ATO electrode. This notable specific capacitance highlights the potential of ATO as an advanced electrode material for supercapacitors, showcasing its suitability for applications requiring rapid charge-discharge cycles and high specific power. This research contributes to the understanding of ATO’s structural and functional aspects, emphasizing its promising role in advancing supercapacitor technology. The synthesized ATO nanoparticles, characterized by their unique morphology and enhanced electrochemical performance, pave the way for cleaner and more efficient energy storage solutions.

Enhancing the Biosorption Potential of Pichia kluyveri FM012 for 4-Bromophenols

AbstractThe use of toxic and persistent pesticides in agriculture results in serious and lasting environmental impacts. Although traditional methods, such as physical and chemical reclamation, yield the best results, treating these contaminants requires a high cost and expertise. Therefore, this study focuses on bioremediation recovery, which is more efficient, economical, and safer for removal. In this case, the newly isolated potential of Pichia kluyveri FM012 in degrading 4-bromophenol was investigated. The impact of optimized parameters such as agitation, pH, nitrogen, and carbon source were also studied. After extensive testing, the best optimal degradation occurred at pH 5 with a stirrer speed of 150 rpm. Glucose and yeast performed the best compared to other carbon and nitrogen sources. The Langmuir model predicted the maximum biosorption capacity (qm = 38.46 mg/g biomass), but the Freundlich model provided a better value of R2 = 0.999. The pseudo-second-order kinetic model was fitting for the study of biosorption kinetics. The FTIR spectrum revealed the presence of asymmetric and symmetric vibrations of the aromatic ring and was assigned to C = C or C = O. Fungi showed biosorption ability across broad functional groups. These results provide interesting information about the ability of Pichia kluyveri FM012 and its potential applications for remediating resistant pesticides.

Minimum norm partial eigenstructure assignment approach for vibration system with time delay

AbstractIn this paper, the minimum norm partial eigenstructure assignment problems (PESAPs) in vibration system with time delay is studied via acceleration‐velocity‐displacement active control. A new explicit solution is given for solving PESAPs using orthogonality relations of symmetric vibration system. A new constructive technique is presented to solve the PESAPs in vibration system with time delay by singular value decomposition method. An optimization algorithm is proposed to solve the minimum norm PESAPs by a quasi‐Newton optimization method. The proposed algorithm works without using the knowledge of receptance matrices and without solving the Sylvester equation. The effectiveness of the proposed algorithm is verified by the results of two numerical examples.

Revealing the Lattice Carbonate Mediated Mechanism in Cu2(OH)2CO3 for Electrocatalytic Reduction of CO2 to C2H4.

Understanding the CO2 transformation mechanism on materials is essential for the design of efficient electrocatalysts for CO2 reduction. In aconventional adsorbate evolution mechanism (AEM), the catalysts encounter multiple high-energy barrier steps, especially CO2 activation, limiting the activity and selectivity. Here, lattice carbonate from Cu2(OH)2CO3 is revealed to be a mediator between CO2 molecules and catalyst during CO2 electroreduction by a 13C isotope labeling method, which can bypass the high energy barrier of CO2 activation and strongly enhance the performance. With the lattice carbonate mediated mechanism (LCMM), the Cu2(OH)2CO3 electrode exhibited ten-fold faradaic efficiency and 15-fold current density for ethylene production than the Cu2O electrode with AEM at a low overpotential. Theoretical calculations and in situ Raman spectroscopy results show that symmetric vibration of carbonate is precisely enhanced on the catalyst surface with LCMM, leading to faster electron transfer, and lower energy barriers of CO2 activation and carbon-carbon coupling. This work provides a route to develop efficient electrocatalysts for CO2 reduction based on lattice-mediated mechanism.

Symmetric and asymmetric free vibrations of rotating eccentric annular plate

The symmetric and asymmetric free vibrations of rotating eccentric annular plate in uniform thermal environment are studied in present paper. The priority of research is clarifying the different combined effects of various factors on symmetric and asymmetric vibrations of eccentric annular plate. In order to conveniently obtain the natural frequency and vibration mode of eccentric annular plate with irregular physical domain, the transformed differential quadrature method is employed. Due to the rotational motion, the initial configuration caused by centrifugal force is calculated before vibration analyses. Then the traveling wave vibration arisen from the Coriolis force is investigated. By comparing the vibration characteristics of annular plate with/without eccentricity, the different impacts of interaction between the geometrical size, boundary conditions, temperature rise, rotational motion, and eccentricity on symmetric and asymmetric vibrations are discussed. Results show that eccentricity leads to the splitting phenomena only in asymmetric vibrations. And it does not affect the symmetry of vibration. Temperature rise results in that the fundamental vibration mode shape shifts from symmetric to asymmetric. However, eccentricity inhibits the change. Rotational motion causes the occurrence of traveling wave vibration in asymmetric vibration whereas not in symmetric vibration.

Exploring the Unusual Reactivity of the Hydrated Electron with CO2.

Many questions remain about the reactions of the hydrated electron despite decades of study. Of particular note is that they do not appear to follow the Marcus theory of electron transfer reactions, a feature that is yet to be explained. To investigate these issues, we used ab initio molecular dynamics (AIMD) simulations to investigate one of the better studied reactions, the hydrated electron reduction of CO2. The rate constant for the hydrated electron-CO2 reaction complex to react to form CO2- is for the first time estimated from AIMD simulations. Results at 298 and 373 K show the rate constant is insensitive to temperature, consistent with the low measured activation energy for the reaction, and the implications of this behavior are examined. The sampling provided by the simulations yields insight into the reaction mechanism. The reaction is found to involve both solvent reorganization and changes in the carbon dioxide structure. The latter leads to significant vibrational excitation of the bending and symmetric stretch vibrations in the CO2- product, indicating the reaction is vibrationally nonadiabatic. The former is estimated from the calculation of an approximate collective solvent coordinate and the free energy in this coordinate is determined. These results indicate that AIMD simulations can reasonably estimate hydrated electron reaction activation energies and provide new insight into the mechanism that can help illuminate the features of this unusual chemistry.

Localized surface plasmon resonance effect of 3-mercaptopropionic acid capped on silver nanoparticles for sensing probe application

Metal nanoparticles such as gold and silver are often used in various nanotechnology applications due to the localized plasmon resonance effect that occurs when incident photons interact with metal nanoparticles. 3-mercaptopropionic acid (3-MPA) is one of the capping molecules that can be provided for surface functionalization on gold or silver core because it has thiol and carboxylic group as a linking biomolecule, and this allows the use of nanoparticles for biosensor applications. In this study, we successfully synthesized silver nanoparticles capped by 3-mercaptopropionic acid (AgMPA) by use of two kinds of methods i.e ligand exchange and direct reduction, which reveal the unique characteristic plasmonic peaks of AgNP around 430 nm and 436 nm, respectively with spherical shape of AgNP and diameter size about 6-20 nm. The transmittance spectra from Fourier Transform Infrared (FTIR) measurement shows that S-H coordination from 3-MPA is invisible after 3-MPA attach on Ag core due to the strong coordination between Ag and the sulfur (S) ion, while the broaden peaks at 1589 and 1385 cm-1 for AgMPA are assigned to asymmetric and symmetric vibrations of carboxylate groups which overlap between carboxylate from citrate and 3-MPA. Finally, the colorimetric detection using AgCA and AgMPA as sensing probe was carried out by use of Biocytin-Avidin system molecule as analyte, which resulted in the colour changed rapidly from yellow to transparent-yellow and the red-shifted of absorbance spectra indicating the attachment of analyte to functionalized molecule of our synthesized AgCA and AgMPA.