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Density, Structure, and Stability of Citrate <sup>3–</sup> and H <sub/>2</sub> Citrate <sup>–</sup> on Bare and Coated Gold Nanoparticles
摘要： We simulate the packing of citrate3– and H2citrate– onto gold nanoparticles (AuNPs) to understand how citrate anions cap and stabilize AuNPs. We determine the molecular configurations of citrate on 4, 6, and 8 nm AuNP surfaces as a function of charge state and packing density and find that both the distribution of configurations and maximum packing density are independent of AuNP size. A combination of molecular dynamics simulations and in situ Fourier transform infrared spectroscopy (FTIR) is employed to compare the molecular configurations, stability, and density of citrate on 4 nm citrate-coated (cit-AuNPs) and within polycation-wrapped 4 nm cit-AuNPs. FTIR experiments indicate the presence of H2citrate– within polycation-wrapped cit-AuNPs with coordination between the H2citrate– layer and polycation layer in agreement with simulations. Intermolecular hydrogen bonding between terminal carboxylic-acid groups of H2citrate– stabilizes the anionic layer at the interface between cit-AuNPs and adsorbing charged molecules. The calculated total density of H2citrate– on AuNPs decreases from 3.3 × 10-10 mol/cm2 to 3.0 × 10-10 mol/cm2 upon adsorption of a polycation due to some displacement of dangling H2citrate– hydrogen bonded to the surface-bound layer. The density of the surface-bound layer is consistently 2.8 × 10-10 mol/cm2 with and without polycation adsorption. We provide all-atom level insight into the distribution and organization of experimentally derived binding modes of citrate on bare and coated cit-AuNPs. The citrate density and surface charge density are determined for all-atom and coarse-grained modeling of cit-AuNPs, their functionalization, and transformations in complex environments.
关键词： polycation adsorption,gold nanoparticles,FTIR spectroscopy,citrate,molecular dynamics simulations
更新于2025-09-23 15:21:21
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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21
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Transient photoinduced phenomena in graphitic carbon nitride as measured at nanoseconds resolution by step-scan FTIR
摘要： Transient FTIR measurements were performed on graphitic carbon nitride using a step-scan method, facilitating temporal resolution of a few nanoseconds. Variations in the location and the intensity of specific peaks and emerging of new peaks were observed during the first 170 nanoseconds after excitation. A comparison was made between graphitic carbon nitride prepared at two temperatures: 510 °C and 650 °C. The material prepared at 650 °C revealed very strong non-specific absorption beginning 35 nanoseconds after excitation and lasting for 20 nanoseconds. This phenomenon, termed “IR-blackening” was observed neither in g-C3N4 prepared at 510 °C nor in g-C3N4 prepared at 650 °C that was exposed to hole scavengers (ethanol and benzyl alcohol). In contrast, exposure of material prepared at 650 °C to an electron scavenger (methyl viologen) hardly alter the “IR-blackening” phenomenon. The results were explained by a mechanism, predicting higher reductive activity for materials having imperfect heptazine polymerization, as indeed was found in the photocatalytic degradation of 4-nitrophenol.
关键词： Photocatalysis,IR- blackening,Step-scan,graphitic carbon nitride,Transient FTIR
更新于2025-09-23 15:21:21
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Ellagitannins in wines: Future prospects in methods of analysis using FT-IR spectroscopy
摘要： Wine aging in wooden barrels can alter a wine’s sensory features through the extraction of wood phenols such as lignins, volatile phenols and hydrolysable tannins. Among the hydrolysable tannins, ellagitannins have been found not only to modify a wine’s sensory character but also to generate new products with compounds already present in wines. For this reason, their quantification is of high importance. However, ellagitannin analysis requires the use of sophisticated equipment and many preparative steps, making their quantification in wines cost effective and laborious. In this study, the feasibility of FT-IR spectroscopy coupled with chemometrics for the quantification of ellagitannin concentration in wines was examined for the first time. Partial Least Squares regression was used to construct calibration models, using the fingerprint region of the spectrum, 1821-950 cm-1 (first derivative in range). The correlation coefficient (R2) was found 0.93, the Root-Mean-Square Error of Calibration RMSEC was 1.17 and the Root-Mean-Square Error of Prediction, RMSEP was 1.57. The results indicate that FT-IR could be used for a quick, non destructive and economical estimation of a wine’s total ellagitannin content.
关键词： barrel,chemometrics,Wine,FTIR,ellagitannins
更新于2025-09-23 15:21:21
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Rapid quantification of clove (Syzygium aromaticum) and spearmint (Mentha spicata) essential oils encapsulated in a complex organic matrix using an ATR-FTIR spectroscopic method
摘要： Essential oils (EOs) are often encapsulated in various and complex matrices to protect them against potential degradation or to control their release. To achieve an optimum use in food products, their rapid and precise quantification after encapsulation and storage is required. Hence, a rapid ATR-FTIR method was developed and tested with two encapsulated essential oils (EOs): clove (Syzygium aromaticum) and spearmint (Mentha spicata);. Despite, the complexity of the matrix, this method coupled with univariate or multivariate regression models exhibited high potential for global quantification of the two encapsulated EOs. For clove EO, in relation to the major presence of eugenol and eugenol acetate, an analysis based on a unique band (1514 cm-1) was sufficient to obtain a good prediction with RMSEP value of 0.0173 g of EO per g of matrix. For spearmint oil which is characterized by numerous terpenoid compound, three bands (799, 885, and 1680–1676 cm-1) were suitable for a good prediction with RMSEP value of 0.0133. ATR-FTIR method was compared with a reference gas chromatography FID quantitative method in an EO release experiment and its efficiency was evaluated through modeling by the Avrami equation. Beside time saving, the ATR-FTIR method was also capable of monitoring the EO profile. This method could be easily adapted as a routine analysis in the EOs industry as quality control.
关键词： Encapsulation,ATR-FTIR,Spearmint,Essential oils,Quantification,Clove
更新于2025-09-23 15:21:21
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Percolation dependent conducting behavior of poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) in the presence of cationic polyelectrolyte
摘要： Conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films is highly modified in the presence of cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC). In-plane electrical conductivity of the thin films of PEDOT:PSS and PDADMAC complex (designated as PED*PDA) are measured for one to five layers, i.e., (PED*PDA)1 to (PED*PDA)5 films prepared by spin-coating method and compared with the pristine PEDOT:PSS films. In addition, PDADMAC and PEDOT:PSS is spin coated on each other to form a bilayer unit (designated as PDA/PED) and one to five layers of such PDA/PED unit, i.e., (PDA/PED)1 to (PDA/PED)5 films are formed by alternate deposition and the conductivity is compared with the complex films. In-plane conductivity of PED*PDA is drastically higher than the pristine PEDOT:PSS and is nearly independent of the layer number, i.e., thickness of the film. However, for PDA/PED films, behavior of conductivity is different in comparison with that of the complex films as the conductivity is found to increase for (PDA/PED)1 to (PDA/PED)2 and then decreases from (PDA/PED)3 to (PDA/PED)5 respectively. With the increase of the applying voltage, the linear nature of I-V curves remain unchanged. The structure, morphology and mechanism of conductivity enhancement are investigated through various characterization techniques. The strong electrostatic attachment between anionic PSS part of PEDOT:PSS and cationic PDADMAC is responsible for the drastic enhancement of conductivity as the percolation pathway enhances.
关键词： PEDOT:PSS,Thin films,Polyelectrolyte,FTIR,Electrical behavior,XRD
更新于2025-09-23 15:21:01
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Optical, Structural and Electrical Studies of Biopolymer Electrolytes Based on Methylcellulose Doped with Ca(NO <sub/>3</sub> ) <sub/>2</sub>
摘要： The intention of this research is to study effect of the different weight percent (wt%) of calcium nitrate, Ca(NO3)2 (CN) salt into biopolymer of Methylcellulose (MC). MC-CN solid biopolymer electrolyte was prepared by using casting technique. The concentrations of CN salt were prepared between 5 to 25 wt%. The optical and electrical characteristics of the samples were study by using Fourier Transform-Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD) and Electrical Impedance Spectroscopy (EIS). The highest conductivity of the samples was containing 25 wt% of CN is 2.21X10-7 Scm-1. The optical study by using FTIR shows that the CN salt act as the conducting ions devoid of effect the molecular structure of the polymer. Additionally, the data of XRD revealed that MC-CN an amorphous phase.
关键词： EIS,Methylcellulose,Biopolymer Electrolytes,FTIR,XRD,Calcium Nitrate
更新于2025-09-23 15:21:01
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Rapid quality assessment of isogams using laser plasma spectroscopy
摘要： In this paper, the quality assessment of isogams is demonstrated by laser-induced breakdown spectroscopy (LIBS) using the comparative standardization method. Here, the mass concentrations of carbon and hydrogen, as basic elements of tar, relative to that of calcium, as an undesired element, are taken into account as principal parameters to determine the quality of isogams. Hence, the intensity ratios of H?? line of hydrogen (656.28?nm), the (0, 0) band of CN (388.34?nm), and the (0, 0) band of C2 (516.52?nm) to the line intensity of once-ionized calcium (317.93?nm) are considered as determinant markers for five different pre-known isogam brands. Qualitatively, classification of the isogams based on this approach is in full agreement with that obtained from the results of Fourier-transform infrared (FTIR) spectroscopy. In FTIR spectra, two stronger transitions of 2849?cm?1 and 2917?cm?1 related to the symmetric and asymmetric stretching vibrations of C–H play the principal role in the analysis of samples. Furthermore, the results obtained from energy-dispersive X-ray (EDX) analysis quantitatively confirm the LIBS outcomes. And finally, to reveal the differences between isogams from various aspects, the linear discriminant analysis (LDA) is exploited as a statistical approach.
关键词： FTIR spectroscopy,EDX analysis,Linear discriminant analysis (LDA),Laser-induced breakdown spectroscopy (LIBS),Isogams,Quality assessment
更新于2025-09-23 15:21:01
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Infrared spectroscopy of live cells from a flowing solution using electrically-biased plasmonic metasurfaces
摘要： Spectral cytopathology (SCP) is a promising label-free technique for diagnosing diseases and monitoring therapeutic outcomes using FTIR spectroscopy. In most cases, cells must be immobilized on a substrate prior to spectroscopic interrogation. This creates significant limitations for high throughput phenotypic whole-cell analysis, especially for the non-adherent cells. Here we demonstrate how metasurface-enhanced infrared reflection spectroscopy (MEIRS) can be applied to a continuous flow of live cell solution by applying AC voltage to metallic metasurfaces. By integrating metasurfaces with microfluidic delivery channels and attracting the cells to the metasurface via dielectrophoretic (DEP) force, we collect the infrared spectra of cells in real time within a minute, and correlate the spectra with simultaneously acquired images of the attracted cells. The resulting DEP-MEIRS technique paves the way for rapid SCP of complex cell-containing body fluids with low cell concentrations, and for the development of a wide range of label-free liquid biopsies.
关键词： dielectrophoretic force,live cells,FTIR spectroscopy,microfluidic delivery channels,Spectral cytopathology,metasurface-enhanced infrared reflection spectroscopy,label-free liquid biopsies
更新于2025-09-23 15:21:01
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Synthesis, DFT studies, fabrication, and optical characterization of the [ZnCMC] <sup>TF</sup> polymer (organic/inorganic) as an optoelectronic device
摘要： A novel carboxymethyl cellulose zinc thin film [ZnCMC]TF was fabricated using the sol–gel technique. Different characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and the optical properties were used to study the properties of [ZnCMC]TF. The molecular structure, FTIR, and optical properties were optimized. The Raman spectrum of the [ZnCMC]TF complex shows several bands in the range of 72–556 cm?1 due to (nZn–O) stretching and (Zn–O) bending, which is an obvious distinction between the FTIR and Raman spectra of [ZnCMC]TF. The optimization was performed using density functional theory (DFT) by DMol3 and Cambridge Serial Total Energy Package (CASTEP) program. The chemical structure was confirmed by spectroscopic and structural properties for both CMC and [ZnCMC]TF; the XRD results showed the same crystal structure (Monoclinic 2). [ZnCMC]TF has a larger grain size than CMC and has a similar behavior in the optical gap energy. The optical constants increased with increasing photon energy, refractive index n, absorption index k, and optical conductivity. The SEM images provide very good evidence in favor of the reaction of zinc transition metal with CMC for the formation of the [ZnCMC]TF complex. The resulting [CMC] spherical thin film and the [ZnCMC]TF polymeric nanorods were examined by different techniques including TEM and EDX. The optical properties obtained from the simulated FTIR, XRD, and CASTEP are in good agreement with those obtained from the experimental studies on CMC and ZnCMC. Based on the optical findings, [ZnCMC]TF is a promising candidate in applications such as solar cells and optoelectronic devices.
关键词： TEM,DMol3,zinc thin film,carboxymethyl cellulose,UV-Vis,DFT,optoelectronic devices,XRD,EDX,CASTEP,sol–gel technique,SEM,FTIR,optical properties,Raman spectroscopy
更新于2025-09-23 15:21:01