Cm-1 Band Research Articles

Analysis and Characterization of Microplastic from Personal Care Products and Surface Water in Bangi, Selangor

Primary microplastics which include microbeads are added into cosmetics and personal care products as scrubbing agent and mostly used because of their uniformity and effective exfoliating properties. However due to their small size, microplastic cannot be filtered by the water treatment plant and flow into our waterways posing a great threat to the aquatic life. Therefore, this study aims to detect the presence of microplastics in personal care products and surface water. Microplastic from personal care samples were extracted using warm water at 60 ⁰C and then characterized using ATR - FTIR to determine the polymer composition. Based on the spectrum, the extracted microplastics were confirmed as polyethylene with significance peaks at 2800 - 2900 cm-1 (C-H stretching) and medium band at 700 cm-1 which indicates the presence of ethylene networks. The extracted microplastics were also identified as polystyrene with the important peaks appear at 3300 and 1600 cm-1 with additional weak peak at 1400 cm-1 which represent C-H aromatic stretching and C=C aromatic group, respectively. Next, SEM method was used to determine the morphology and size of the microplastics which give sizes ranging from 200-500 µm for each sample. Furthermore, optical microscope was used to determine the color and shape of the microbeads. The results showed that extracted microbeads come from various colors such as white, purple, pink, brown and colorless while the shape observed was spherical, granular, and irregular. Next, insect net and bucket techniques were used in sampling of surface water. The successfully filtered solids were analysed using WPO method and characterize by ATR-FTIR technique. The microplastics found in surface water sample were from various shape including fragment, film, pellet, foam, and tube with the majority come from PE type polymer plastic. Hence, this study proved the presence of microplastic in personal care products that available in Malaysia as well as in surface water.

Physicochemical studies of nanocrystals of starches from two rice (Oryza sativa L.) types and their characteristics using various modern instrument techniques.

Starch nanocrystals have received considerable attention, due to their biodegradability, nontoxicity and renewable and abundant sources. The objective of this research is to compare the morphology, physicochemical characteristics and rheological properties of native (NSNC) and waxy rice starch nanocrystals (WSNC). Both NSNC and WSNC exhibited a platelet-like shape, and they tended to show square-like platelet morphology with increasing initial amylopectin content. Compared to native starches, three weight loss stages of NSNC and WSNC in thermogravimetric analysis curves were observed, while the thermal depolymerization of NSNC started earlier than that of WSNC. The relative crystallinity of NSNC and WSNC was 38.6% and 48.3%, respectively, which were markedly higher than that of native starches. Fourier transform infrared spectra revealed that NSNC presented the highest ratio of 1045/1014 cm-1 bands among the tested samples, which was probably due to the re-association of retrograded amylose to double-helices structure in NSNC. Moreover, the introduction of sulfur atoms on the surface of NSNC and WSNC was confirmed from the results of X-ray photoelectron spectroscopy. At 5% (w/v) and 10% (w/v) concentration levels, all SNC suspensions exhibited a shear-thinning behavior as the shear rate increased from 0.1 to 100 s-1 . Starch nanocrystals obtained from native and waxy rice starch can be potentially used as reinforcement in biodegradable nanocomposites for packaging, fat replacers, thickening agents and emulsion stabilizers. © 2020 Society of Chemical Industry.

Ratiometric Sensing of Polycyclic Aromatic Hydrocarbons Using Capturing Ligand Functionalized Mesoporous Au Nanoparticles as a Surface-Enhanced Raman Scattering Substrate.

The absorption behavior between plasmonic nanostructures and a target molecule plays key roles in effective surface-enhanced Raman scattering (SERS) detection. However, for analytes with low surface affinity to the metallic surface, e.g., polycyclic aromatic hydrocarbons (PAHs), it remains challenging to observe the enhanced Raman signal. In this work, we reported a ratiometric SERS strategy for sensitive PAH detection through the surface functionalization of 3D ordered mesoporous Au nanoparticles (meso-Au NPs). By employing mono-6-thio-β-cyclodextrin (HS-β-CD) as capture ligands, the hydrophobic molecules, e.g., anthracene, could be effectively absorbed on the meso-Au NP surface via a host-guest interaction. Besides, a hydrophobic slippery surface is used as a concentrator to deliver and enrich the Au/analyte droplets into a small area. Consequently, the detection limits of anthracene and naphthalene are down to 1 and 10 ppb. The improved SERS enhancement is mainly ascribed to the host-guest effect of HS-β-CD ligands, large surface area and high-density of sub-10 nm mesopores of Au networks, as well as the enrichment effect of hydrophobic slippery surface. Moreover, the HS-β-CD (480 cm-1 band) could serve as an internal standard, leading to the ratiometric determination of anthracene ranging from 1 ppm to 1 ppb. The proposed surface modification strategy in combination with the hydrophobic slippery surface shows great potential for active capture and trace detection of persistent organic pollutants in real-world SERS applications.

GROWTH, CARBOHYDRATE PRODUCTIVITY AND GROWTH KINETIC STUDY OF Halochlorella rubescens CULTIVATED UNDER CO2-RICH CONDITIONS

This study was parametrically established to investigate the effect of different initial pH cultivation medium from pH 4.00 to pH 10.00 and CO2 concentration from 0.04% to 25% (v/v) on the growth and carbohydrate content of Halochlorella rubescens. Changes in biochemical compositions were also analysed using Fourier-transform infrared spectroscopy (FTIR). The maximum concentration of biomass and the productivity carbohydrate were 0.49 ± 0.01 g/L and 22.42 ± 0.03 mg/L.d respectively, when pH 10.00 and 5% (v/v) CO2 concentration were used for cultivation. The FTIR analysis revealed obvious changes in the chemical functional groups for the1200-900 cm-1, 1655 cm-1 and 2850 cm-1 bands, which represent carbohydrate, protein and lipid in microalgal biomass under different cultivation conditions. At the completion of this study, two kinetic growth models, Logistic and Gompertz were evaluated for microalgae growth at elevated condition. The kinetic model analysis for Halochlorella rubescens growth at high CO2 condition fit well with the Gompertz equation with R2 value of 0.9977. The data acquired from this research was helpful for predicting the growth characteristics of microalgae in a CO2-rich medium and could act as an essential platform for the production of chemicals and biofuels

FLIm-Guided Raman Imaging to Study Cross-Linking and Calcification of Bovine Pericardium.

Bovine pericardium (BP) is a vascular biomaterial used in cardiovascular surgery that is typically cross-linked for masking antigenicity and enhance stability. There is a need for biochemical evaluation of the tissue properties prior to implantation to ensure that quality and reliability standards are met. Here, engineered antigen removed BP (ARBP) that was cross-linked with 0.2% and 0.6% glutaraldehyde (GA), and further calcified in vitro to simulate graft calcifications upon implantation was characterized nondestructively using fluorescence lifetime imaging (FLIm) to identify regions of interest which were then assessed by Raman spectroscopy. We observed that the tissue fluorescence lifetime shortened, and that Raman bands at 856, 935, 1282, and 1682 cm-1 decreased, and at 1032 and 1627 cm-1 increased with increasing GA cross-linking. Independent classification analysis based on fluorescence lifetime and on Raman spectra discriminated between GA-ARBP and untreated ARBP with an accuracy of 91% and 66%, respectively. Pearson's correlation analysis showed a strong correlation between pyridinium cross-links measured with high-performance liquid chromatography and fluorescence lifetime measured at 380-400 nm (R = -0.76, p = 0.00094), as well as Raman bands at 856 cm-1 for hydroxy-proline (R = -0.68, p = 0.0056) and at 1032 cm-1 for hydroxy-pyridinium (R = 0.74, p = 0.0016). Calcified areas of GA cross-linked tissue showed characteristic hydroxyapatite (959 and 1038 cm-1) bands in the Raman spectrum and fluorescence lifetime shortened by 0.4 ns compared to uncalcified regions. FLIm-guided Raman imaging could rapidly identify degrees of cross-linking and detected calcified regions with high chemical specificity, an ability that can be used to monitor tissue engineering processes for applications in regenerative medicine.

Effect of Controlled Humidity and Tissue Hydration on Colon Cancer Diagnostic via FTIR Spectroscopic Imaging.

The effects of hydration on the DNA conformation in the colon biopsy tissues at different disease stages, hyperplasia, dysplasia, and cancer, and their subsequent classifications were investigated in this study. FTIR spectroscopic imaging was used to study the tissues while controlling the humidity from 16% RH to 88% RH using saturated salt solutions. A nonuniform uptake of water into the tissue at its maximum hydrated state was observed in the chemical images showing the distribution of the absorbance of the νas OH spectral band. The regions of high absorbance of this band in the tissues overlap with the regions of high absorbance of predominantly the phosphate (1143-1100 cm-1) and lipid (2879-2844 cm-1) bands. Analysis of the second derivative spectra of the hydrated and dehydrated colon tissues further revealed significant peak shifts and changes in absorbance of the spectral bands that correspond to the vibrations of the phosphate group of DNA. These findings showed some disparities when compared to the effect of hydration on the infrared spectra of live cells and pure isolated DNA, possibly due to the presence of DNA mostly in its A-form in the formalin fixed tissues. Coupled with principal component analysis, the spectral biomarkers that differentiate the healthy colon tissues from the diseased tissues were identified to be in the phosphodiester spectral region (1300-1000 cm-1). This differentiation varied under different humidity conditions, with the highest sensitivity of ∼98% found at the dehydrated state of the tissues with random forest supervised classification.

Efecto de la temperatura en multicapas de grafeno usando espectroscopia Raman y equipo de bajo costo

Efecto de la temperatura en multicapas de grafeno usando espectroscopia Raman y equipo de bajo costo Luis G. Hardt1, Juliana B. Rodrigues1, Dionathan A. Campanelli1, Lizandro B. R. Zegarra2, José, W. Kaehler1, Jacson W. Menezes1, Luis E. G. Armas1 1 Universidade Federal do Pampa-Campus Alegrete, Av. Tiarajú 810- Bairro Ibirapuitã, Alegrete-RS, Brasil 2 Universidad Nacional del Santa-UNS, Av. Pacífico 508-Nuevo Chimbote, Chimbote, Perú Recibido el 15 de noviembre del 2019. Aceptado el 3 de marzo del 2020 DOI: https://doi.org/10.33017/RevECIPeru2020.0005/ Resumen Propiedades térmicas de materiales bidimensionales tal como monocapas o multicapas de grafeno han atraído una atención especial, debido a que son excelentes conductores térmicos y sus propiedades térmicas han atraído una atención en particular [1, 2]. En este sentido, en este trabajo se reporta el efecto de la temperatura en las bandas G (~1580 cm-1), 2D (~2700 cm-1) y 2D’ (~3244 cm-1) de los espectros Raman de multicapas de grafeno (MLG) usando espectroscopia Raman y un dispositivo de temperatura de bajo costo. Para esta finalidad las muestras de grafeno fueron depositadas sobre substratos de SiO2 usando el método de exfoliación micro mecánica, en tanto que, el dispositivo de temperatura de bajo costo fue construido usando una fuente reguladora de voltaje y corriente, una resistencia de nicrom, la cual fue colocada sobre una base aislante, acoplada a la base del microscopio Raman. La temperatura en las muestras fue aumentada, en diferentes intervalos, desde la temperatura ambiente (~25 oC) hasta 535 oC, siendo medida en tiempo real usando una cámara térmica. Resultados de este trabajo muestran, que a medida que la temperatura aumenta, la posición de las bandas G (Pos(G)), 2D (Pos (2D)) y 2D’ (Pos (2D’)) son desplazadas a menores números de onda, mostrando un comportamiento no linear. De forma semejante también fue observado un aumento de la anchura a media altura (FWHM) de las bandas G, 2D y 2D’. Estos desplazamientos son explicados en términos de la interacción electrón – fonón y fonón – fonón [3, 4]. Al mismo tiempo, con este trabajo se muestra que usando equipos de bajo costo es posible obtener mejores o iguales resultados a los obtenidos de costo elevado, y serían de grande utilidad para comprender las propiedades térmicas y los mecanismos físicos relacionados con multicapas de grafeno para aplicaciones de dispositivos térmicos que operen a temperatura ambiente. Descriptores: grafeno, temperatura, espectroscopia Raman, propiedades anarmónicas, fonones Abstract Thermal properties of two-dimensional materials such as monolayers or multilayers of graphene have attracted special attention, because they are excellent thermal conductors and their thermal properties have attracted a particular attention [1, 2]. In this sense, in this work the effect of temperature on the G (~ 1580 cm-1), 2D (~ 2700 cm-1) and 2D '(~ 3244 cm-1) bands of multilayer graphene (MLG) is reported using Raman spectroscopy and a low cost temperature device. For this purpose the graphene samples were deposited on SiO2 substrates using the micro-mechanical exfoliation method, while the low-cost temperature device was constructed using a voltage and current regulator source, a microm resistance, which it was placed on an insulating base, coupled to the base of the Raman microscope. The temperature on the samples was increased, at different intervals, from room temperature (~ 25 oC) to 535 oC, being measured in real time using a thermal chamber. Results of this work show that, as the temperature increases, the position of the G (Pos (G)), 2D (Pos (2D)) and 2D '(Pos (2D')) bands are shifted to smaller wavenumbers, showing a non-linear behavior. Similarly, an increase in the full width half maximum (FWHM) of the G, 2D and 2D’ bands was also observed. These displacements are explained in terms of the electron - phonon and phonon - phonon interactions [3, 4]. At the same time, this work shows that using low-cost equipment it is possible to obtain better or equal results than those obtained at high cost, and would be of great utility to understand the thermal properties and physical mechanisms related to graphene multilayers for applications as thermal devices operating at room temperature.

Spatial Ordering of the Structure of Polymer-Capped Gold Nanorods under an External DC Electric Field.

We studied the alignment changes of polymer-capped gold nanorods (GNRs@PS) under an applied electric field by visible-near-infrared absorption and small-angle X-ray scattering (SAXS) measurements. Monodispersed GNRs with an aspect ratio of 4.0 were produced by the seed-mediated growth method using cetyltrimethylammonium bromide and sodium oleate binary surfactants. We investigated the phase transition between the ordered structure of GNRs@PS induced by the external electric field. At appropriate field strengths (>3 V/μm), the SAXS profiles of GNRs@PS showed a smectic ordered structure. Increasing the electric field strength densified the ordered structure and greatly increased the Raman signals (the 298 and 445 cm-1 bands) of the carbon tetrachloride (solvent) between the GNRs@PS. The insights gained are potentially applicable to catalysts, future displays, optical filters, and data storage devices.

Elucidating the Electronic Structure of High-Spin [MnIII(TPP)Cl] Using Magnetic Circular Dichroism Spectroscopy.

Manganese porphyrins are used as catalysts in the oxidation of olefins and nonactivated hydrocarbons. Key to these reactions are high-valent Mn-(di)oxo species, for which [Mn(Porph)(X)] serve as precursors. To elucidate their properties, it is crucial to understand the interaction of the Mn center with the porphyrin ligand. Our study focuses on simple high-spin [MnIII(TPP)X] (X = F, Cl, I, Br) complexes with emphasis on the spectroscopic properties of [MnIII(TPP)Cl], using variable-temperature variable-field magnetic circular dichroism spectroscopy and time-dependent density functional theory to help with band assignments. The optical properties of [MnIII(TPP)Cl] are complicated and unusual, with a Soret band showing a high-intensity feature at 21050 cm-1 and a broad band that spans 23200-31700 cm-1. The 15000-18500 cm-1 region shows the Cl(px/y) → dπ (CT(Cl,π)), Q band, and overlap-forbidden Cl(px/y)_dπ → dx2-y2 transitions that gain intensity from the strongly allowed π → π*(0) transition. The 20000-21000 cm-1 region displays the prominent pseudo A-type signal of the Soret band. The strongly absorbing features at 22500-28000 cm-1 exhibit A1u⟨79⟩/A2u⟨81⟩ → dπ, CT(Cl,π/σ), and symmetry-forbidden CT character, mixed with the π → π*(0) transition. The strong dx2-y2_B1g⟨80⟩ orbital interaction drives the ground-state MO mixing. Importantly, the splitting of the Soret band is explained by strong mixing of the porphyrin A2u(π)⟨81⟩ and the Cl(pz)_dz2 orbitals. Through this direct orbital pathway, the π → π*(0) transition acquires intrinsic metal-d → porphyrin CT character, where the π → π*(0) intensity is then transferred into the high-energy CT region of the optical spectrum. The heavier halide complexes support this conclusion and show enhanced orbital mixing and drastically increased Soret band splittings, where the 21050 cm-1 band shifts to lower energy and the high-energy features in the 23200-31700 cm-1 range increase further in intensity, compared to the chloro complex.

Changes in IR band areas and band shifts during water adsorption to lecithin and ceramide.

Adsorption of water to a phospholipid (lecithin) and a ceramide were studied by IR microspectroscopy equipped with a humidity control system and quartz crystal microbalance (QCM). The water weight ratios increase up to 12.2 wt% for lecithin and 1.2 wt% for ceramide at RH ~80%, with linear correlations with infrared OH (+NH) band areas. For lecithin, the 1230 cm-1 band (PO2-) and the 1735 cm-1 band (CO) shift to lower wavenumbers, while the 1060 cm-1 band (PO2-, POC) shift to higher wavenumber with RH. Band areas of phosphates (1230 and 1060 cm-1) increase with RH showing positive relations with the band area of bound water. Bound water molecules with shorter H bonds might be bound to these phosphate groups. Band areas of aliphatic CHs are negatively correlated with the increasing adsorption of free water. Free water molecules with longer H bonds might interact loosely with aliphatic chains of lecithin. For ceramide, only the 1045 cm-1 band (CO) shows a small red shift at higher RHs than 60%, indicating adsorption of bound water to CO bonds. Amounts of water molecules adsorbed to ceramide are very limited due to few adsorption of free water.

SERS assessment of the cancer-specific methylation pattern of genomic DNA: towards the detection of acute myeloid leukemia in patients undergoing hematopoietic stem cell transplantation.

In this label-free surface-enhanced Raman scattering (SERS) study of genomic DNA, we demonstrate that the cancer-specific DNA methylation pattern translates into specific spectral differences. Thus, DNA extracted from an acute myeloid leukemia (AML) cell line presented a decreased intensity of the 1005 cm-1 band of 5-methylcytosine compared to normal DNA, in line with the well-described hypomethylation of cancer DNA. The unique methylation pattern of cancer DNA also influences the DNA adsorption geometry, resulting in higher adenine SERS intensities for cancer DNA. The possibility of detecting cancer DNA based on its SERS spectrum was validated on peripheral blood genomic DNA samples from n = 17 AML patients and n = 17 control samples, yielding an overall classification of 82% based on the 1005 cm-1 band of 5-methylcytosine. By demonstrating the potential of SERS in assessing the methylation status in the case of real-life DNA samples, the study paves the way for novel methods of diagnosing cancer. Graphical abstract.

Fabrication and SERS performance of silver nanoarrays by inkjet printing silver nanoparticles ink on the gratings of compact disc recordable.

Silver nanoarrays were fabricated by inkjet printing silver nanoparticles ink on the gratings of compact disc recordable (CD-R). Rhodamine 6G (R6G) was chosen as a probe molecule to evaluate their surface-enhanced Raman scattering (SERS) performance. The finite-difference time domain (FDTD) solution was used to simulate local electric field distribution of silver nanoparticles on the grating surface and flat surface, respectively. It was found that the Ag/grating substrate possessed higher enhancement ability than the Ag/flat due to the high-density hot spots of periodic structure of the grating. The silver nanoarrays substrate exhibited high stability and the characteristic peaks of R6G can be still well observed after eight months. The substrate also exhibited a good spot-to-spot reproducibility with an RSD of 10.21% by eight points. SERS mappings of R6G adsorbed on silver nanoarrays were tested under the ultra-fast Raman imaging mode, and the relative standard deviation (RSD) values of uniformity were calculated to be 8.35% and 11.53% at 610 cm-1 band measured by 2500 and 6480 points, respectively. In addition, the as-prepared silver nanoarrays was successfully applied to the detection of melamine in adult milk powder solution directly. A good linear relationship with the correlation coefficient of 0.9968 between peak intensity and concentration was obtained from 1.2 to 100 mg/L.

Photo-Induced Ring-Opening Reaction of Flav-3-en-2-ol Monitored by Time-Resolved Infrared Spectroscopy.

Photo-induced ring-opening reaction from flav-3-en-2-ol to 2-hydroxychalcone has been studied by time-resolved infrared (TR-IR) spectroscopy and quantum chemical calculations. A vibrational band due to the C═O stretching modes for intermediate species, enol forms of 2-hydroxychalcone in the electronic ground state, was observed at 1632 cm-1 in the TR-IR spectra after photoexcitation of flav-3-en-2-ol. We also found that the C═O stretching modes of the keto forms of 2-hydroxychalcone at 1664 cm-1 appeared immediately after photoexcitation and increased in intensity in synchronization with the depletion of the 1632 cm-1 band. Because the decay of the 1632 cm-1 band and the rise of the 1664 cm-1 band were fitted with bi-exponential model functions with common rate constants 0.5 and 11 μs-1, we propose that two kinds of enol form, single bond cis- (s-cis-) and trans- (s-trans-) enols, transformed into keto forms, cis-2-hydroxychalcone (Cc) and trans-2-hydroxychalcone (Ct), respectively. Quantum chemically calculated IR spectra of related species are consistent with the proposal. The observed temporal behavior of the TR-IR spectra indicates that there were reaction paths to the photogeneration of Cc and Ct within the time resolution of the TR-IR spectrometer (∼0.1 μs) in addition to the reaction paths via the enol forms of 2-hydroxychalcone.

Synthesis and Raman spectra of K-Ca double carbonates: K2Ca(CO3)2 bütschliite, fairchildite, and K2Ca2(CO3)3 at 1 ATM

Here we present results on synthesis of double K-Ca carbonates at atmospheric pressure in closed graphite capsules. The mixtures of K2CO3 and CaCO3 corresponding to stoichiometry of K2Ca(CO3)2 and K2Ca2(CO3)3 were used as starting materials. The low-temperature modification of K2Ca(CO3)2 was synthesized by a solid-state reaction at 500°C during 96 h. The high-temperature modification of K2Ca(CO3)2 as well as the K2Ca2(CO3)3 compound were synthesized both by a solid-state reaction at 600°C during 72 h and during cooling of the melt from 830 to 650°C for 30 min. The obtained carbonates were studied by Raman spectroscopy. The Raman spectrum of bütschliite is characterized by the presence of an intense band at 1093 cm-1 and several bands at 1402, 883, 826, 640, 694, 225, 167 and 68 сm-1. The Raman spectrum of fairchildite has characteristic intense bands at 1077 and 1063 cm-1, and several bands at 1760, 1739, 719, 704, 167, 100 сm-1. In the Raman spectrum of K2Ca2(СO3)3 intense bands at 1078 and 1076 cm-1 and several bands at 1765, 1763, 1487, 1470, 1455, 1435, 1402, 711, 705, 234, 221, 167, 125 and 101 сm-1 were found. The collected Raman spectra can be used to identify carbonate phases entrapped as microinclusions in phenocrysts and xenoliths from kimberlites and other alkaline rocks.

Liver changes induced by cadmium poisoning distinguished by confocal Raman imaging

Heavy metal pollution has become an important issue threatening human health and the liver is a very important metabolic organ. Here, we use label-free Raman confocal imaging to study the alterations of the liver tissue after cadmium pollution. Raman imaging has been performed on 100μmx100μm liver tissues to study the distribution of important macromolecules and the average Raman spectrum of the entire region has been used to characterize and quantize the change of biochemical compositions in liver tissue. The poisoned livers displayed a significant decrease in the intensity of 748 cm-1, 1128 cm-1 and 1585 cm-1 bands of cytochrome C, in comparison to the control. The collagen peak at 1082 cm-1 is significantly higher than that of control, suggesting the increasing fibrosis of Cd liver tissues. To confirm the results, we selected a 30μmx15μm liver cell area for high-resolution Raman imaging. We observed a substantial increase of lipids and proteins at specific points of hepatocytes. The confocal Raman imaging of liver tissues provided a unique tool to better understand disease-induced changes in the biochemical phenotype of primary liver tissues. Our study provides valuable references as in vitro models for studying Cd accumulation and toxicity in human liver.

Porous alumina aerogel with tunable pore structure for facile, ultrasensitive, and reproducible SERS platform

AbstractPorous alumina aerogel synthesized by sol–gel method was used as facile and sensitive surface‐enhanced Raman scattering (SERS) platform. In a simple “drop‐test” SERS detection, low concentration dye solution mixed with silver nanoparticles was directly dropped on the surface of aerogel platform for SERS detection immediately. The pore structure of alumina aerogel was tuned by adding PEG‐400 and varying the gelation temperature. The effects of surface morphology and pore size of alumina aerogel platform on SERS performance of crystal violet (CV) were investigated. The result shows that large specific surface area and interconnected pore network of aerogel are helpful for fast permeation of solution, generation of “hot spots,” and adsorption of probe molecules. The Raman signal of CV was largely enhanced, enabling a detection concentration to 5 × 10−10 M with a SERS enhancement factor of 3.4 × 107. The SERS enhancement of alumina aerogel platform is remarkably improved with the increase of specific surface area and pore size, which is also confirmed by the finite‐difference time‐domain simulation. Moreover, the relative standard deviation of SERS intensity at 1619 cm-1 band for 5 × 10−8 M CV on aerogel platform is about 12%, indicating a good reproducibility.

Measuring Molecular Strain in Rewetted and Never-Dried Eucalypt Wood with Raman Spectroscopy.

To measure growth strain in wood using Raman spectroscopy, we investigated the Raman spectra of rewetted (water-saturated) Eucalyptus regnans and green Eucalyptus quadrangulata wood during tensile tests. Partial least squares models to predict the tensile strain were built from the Raman spectra. The best model could predict the tensile strain with a root mean square error of 427.5 με. Apart from the widely reported band shift at 1095 cm-1 upon mechanical strain, spectral changes at 1420, 1120, 895, and 456 cm-1 were identified. The assignments of these bands were discussed in relation to the molecular deformation of cellulose. The band shift rates during tensile tests were -3.06 and -2.15 cm-1/% for rewetted E. regnans and green E. quadrangulata wood, respectively. We successfully detected the release of the molecular growth strain in green eucalyptus wood with Raman spectroscopy by observing band shifts of the 1095 cm-1 signal. Further, there was a moderate correlation (r = 0.48) between the growth strain measured with strain gauges and the 1095 cm-1 band position. The precision of the prediction of growth strain using Raman spectroscopy was negatively affected by variation attributed to the inhomogeneity of wood on the millimeter scale and instrumental instability.

Infrared Study of the O–H Stretching Vibration in Sr-Doped LaMO3 (M=Co, Yb, Gd) Cathode Materials

The effect of the B site species in ABO3 perovskite oxides was investigated by infrared analysis. Cathode materials such as Sr-doped LaMO3 (M=Co, Yb, Gd) were synthesized with the sol-gel method. The O–H stretching vibration was observed in the ranges of 2800-3800 cm-1 (band A and band B) due to Sr‒OH‒La and 1800-2500 cm-1 (band C and band D) due to Sr‒OH‒Sr. The O–H stretching vibration could be found in the band A, band B, and band C in the proton conducting material La0.9Sr0.1YbO3-δ, and La0.9Sr0.1GdO3-δ. On the other hand, only band C could be observed in oxide ion conducting material La0.9Sr0.1CoO3-δ. It is indicated that protons difficulty dissolved into oxide ion conducting material.

Extracción y caracterización de quitina de escamas de tilapia roja (oreochromis sp.) del Huila mediante métodos químicos

La quitina es el segundo biopolímero lineal más importante en el mundo. Avances recientes sugieren que la quitina se puede obtener de las escamas de peces. Para este artículo, se utilizaron tres tratamientos diferentes para obtener quitina de las escamas de tilapia roja (Orechromis sp.). Todas las muestras fueron insolubles en los solventes y ácidos usados; también presentaron diferentes porcentajes de carbono (3,27-55,80 %), oxígeno (22,09-42,51 %), nitrógeno (11,61-11,81 %), P (1,08-22,2 %), Ca (1,26-26,11 %), Na (0,53-1,02 %) y Mg (0,26-0,91 %). Las bandas de 3.340 cm-1 presentes en el espectro de infrarrojo corresponden al grupo hidroxilo de las bases de glucosamina poliméricas y los picos 1.415-1.456 cm-1 están relacionados con la banda N-H característica del grupo funcional amida. Las imágenes (SE) muestran diferentes dimensiones de partículas (0,1-30 μm) y las masas moleculares promedio, Mw, para Ch1, Ch2 y Ch3 fueron 1.064,28; 1.064,56; y 823,428, respectivamente, con una polidispersidad de 1,0074.

Assignment of Infrared-Active Combination Bands in the Vibrational Spectra of Protonated Molecular Clusters Using Driven Classical Trajectories: Application to N4H+ and N4D+

We investigate the utility of the driven molecular dynamics (DMD) approach to complex molecular vibrations by applying it to linear clusters with several degenerate vibrational modes and infrared (IR) intense combination bands. Here, the prominent features in N4H+ and N4D+ IR spectra, reported and described by others previously, have been characterized for the first time by DMD using recently published high-level potential and dipole moment surfaces. Namely, the calculations closely correlate the parallel proton stretch vibration in N4H+, at 750 cm-1, with the one observed experimentally at 743 cm-1. Second, the intense IR-active combination bands found in experimental spectra within 900-1100 cm-1 have been properly recovered by DMD at 950 cm-1 as strongly IR-active and confirmed as consisting of H+ asymmetric stretch and N2···N2 intermolecular symmetric stretch modes. Furthermore, we show that certain combination bands involving overtone transitions may be recovered by DMD using a hard-driving regime, such as the 1409 cm-1 band measured in N4H+, revealed by DMD at 1375 cm-1, and assigned to a progressive combination of the parallel H+ stretch and two quanta of N2···N2 stretch, in agreement with quantum mechanical studies reported previously by others.