Search

The analysis of body fluids is desirable to minimize the invasiveness of diagnostic tests and non-destructive forensic investigations. In this study, surface-enhanced Raman spectroscopy (SERS) is employed for sensitive and reproducible detection of biomolecule focusing on 'hot spots' generation and automated flow system. Here, we have demonstrated how the plasmon frequency of nanoparticles can be tuned using different aggregating agents for optimal SERS signals. We have compared the effect of different aggregating agents on silver colloids and the resulting enhancement in Raman signals for Tryptophan which is an important amino acid present as an integral component of various body fluids including blood, saliva, tears, and cerebrospinal fluid. The automated segmented flow system, Lab-on-a-chip (LOC), is employed to trap the analyte in droplets while obtaining reproducible SERS spectra of Tryptophan at μM concentration. Further for a thorough interpretation of enhanced vibrational modes of Tryptophan, a theoretical approach has been applied. By combining both experimental and computational approaches we have identified the most preferable site of Tryptophan for interaction with metal nanoparticles and accurately assigned the enhanced Raman bands. The present study demonstrates that the union of SERS and microfluidics has the potential for spectral fingerprinting of biomolecules present in body fluids with high sensitivity. [ABSTRACT FROM AUTHOR]

Aerogels are a unique class of nanoporous ultralight materials exhibiting wide range of textural characteristic properties and tunable porosities. Due to their remarkable features such as low density, high surface area, low refractive index, small thermal conductivity, low dielectric constant and low sound velocity, they exhibit a wide range of applications in different areas such as electronics, thermal and acoustic insulation, chemistry, biomedicine and optics. The special advantages of these materials are that they can be produced in different forms such as monoliths/granular, bead/microspheres, thin films or sheets and as blankets. Aerogels are found to be potential materials for the removal of CO2 through adsorption or electrochemical reduction. There is a plethora of research on different kinds of aerogels used for CO2 adsorption process. Research has been going on toward the development of aerogel-based electrocatalyst, which can be used for valorization of CO2 through electrochemical reduction methods. Although most of the review papers have covered applications of aerogels in CO2 capture, very few discuss the processing of aerogels, more so on their applications in CO2 valorization. In this review, we have collated literature of different forms of aerogels currently available and the steps involved in their fabrication process. In addition, we have covered applications of aerogels in CO2 capture. Furthermore, we focussed on the basic principles involved in the development of an aerogel electrocatalyst as well as recent developments of aerogels in electrochemical CO2 reduction. [ABSTRACT FROM AUTHOR]

Genomic deoxyribounucleic acid (DNA) extracted from Brucella and Bacillus genera including Bacillus anthracis was investigated for the first time using Raman spectroscopy coupled with deep learning technique. Since DNA sequence is unique and independent of growth phases of bacteria, Raman spectroscopy can be a potential molecular diagnostic tool to identify different pathogens. Additionally, pure cellular components such as DNA provide pure Raman spectra and are not corrupted by spectral features from other cell components which is usually the case in whole organism detection. In this work, 15 DNA samples (two from Brucella genus and 13 from Bacillus genus) were studied. Raman signatures revealed unique features for Brucella and Bacillus genus bacteria. We propose an artificial intelligence (AI) based method, convolutional neural network (CNN) to discriminate all 15 DNA samples. The results reveal that Bacillus anthracis has distinct Raman DNA signatures compared to Bacillus cereus and Bacillus thuringiensis and could be discriminated from the latter two using principal component analysis (PCA), hierarchical cluster analysis (HCA), principal component‐linear discriminant analysis (PC‐LDA). In addition to these multivariate analysis techniques, we show that using convolutional neural network (CNN) architecture all 15 DNA samples could be discriminated with 100% accuracy. [ABSTRACT FROM AUTHOR]

Development of novel materials and methodologies for removal of toxic and poisonous carbon monoxide (CO) gas is important to solve serious health and environmental related problems. Existing materials used for the removal of CO gas are quite expensive and therefore, the synthesis of low‐cost and earth‐abundant catalyst for CO oxidation is urgently needed. In the present work, we report the preparation of Pd nanoparticles loaded on porous carbon supports from the spent Pd/C and the subsequent catalytic oxidation of CO. Different Pd based catalysts are prepared by using various reducing agents with different reduction potential such as formaldehyde, green tea, ascorbic acid, and sodium borohydride. The prepared catalysts are characterized and employed for the oxidation of CO. All the prepared catalysts show excellent activity towards CO oxidation at room temperature either in presence or absence of moisture depending on the Pd0/Pd+2 ratio in Pd/C which follows the order Pd/C−NaBH4>Pd/C−HCHO>Pd/C−Ascorbic acid>Pd/C−Green tea. Experimental findings of the present work also reveal that depending on the oxidation state, and moisture plays a critical role in Pd catalytic properties on the oxidation of CO. Theoretical calculations performed using Vienna ab initio Simulation Package (VASP) support the experimental observations and further confirm that the reaction proceeds through Langmuir‐Hinshelwood mechanism. [ABSTRACT FROM AUTHOR]

In conventional Raman spectroscopic measurements of liquids or surfaces the preferred geometry for detection of the Raman signal is the backscattering (or reflection) mode. For non-transparent layered materials, sub-surface Raman signals have been retrieved using spatially offset Raman spectroscopy (SORS), usually with light collection in the same plane as the point of excitation. However, as a result of multiple scattering in a turbid medium, Raman photons will be emitted in all directions. In this study, Monte Carlo simulations for a three-dimensional layered sample with finite geometry have been performed to confirm the detectability of Raman signals at all angles and at all sides of the object. We considered a non-transparent cuboid container (high density polyethylene) with explosive material (ammonium nitrate) inside. The simulation results were validated with experimental Raman intensities. Monte Carlo simulation results reveal that the ratio of sub-surface to surface signals improves at geometries other than backscattering. In addition, we demonstrate through simulations the effects of the absorption and scattering coefficients of the layers, and that of the diameter of the excitation beam. The advantage of collecting light from all possible 4π angles, over other collection modes, is that this technique is not geometry specific and molecular identification of layers underneath non-transparent surfaces can be obtained with minimal interference from the surface layer. To what extent all sides of the object will contribute to the total signal will depend on the absorption and scattering coefficients and the physical dimensions. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Interaction of adsorbate on chargedsurfaces, orientation of theanalyte on the surface, and surface enhancement aspects have beenstudied. These aspects have been explored in details to explain thesurface-enhanced Raman spectroscopic (SERS) spectra of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW or CL-20), a well-known explosive, and 2,4,6-trinitrotoluene(TNT) using one-pot synthesis of silver nanoparticles via biosyntheticroute using natural precursor extracts of clove and pepper. The biosynthesizedsilver nanoparticles (bio Ag Nps) have been characterized using UV–visspectroscopy, scanning electron microscopy and atomic force microscopy.SERS studies conducted using bio Ag Nps on different water insolubleanalytes, such as CL-20 and TNT, lead to SERS signals at concentrationlevels of 400 pM. The experimental findings have been corroboratedwith density functional computational results, electrostatic surfacepotential calculations, Fukui functions and ζ potential measurements. [ABSTRACT FROM AUTHOR]

We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials. [ABSTRACT FROM AUTHOR]

Different reducing agents such as green tea, sodium borohydride, formic acid and ascorbic acid are considered to control the oxidation state of Pd in the Pd/C catalyst. Keywords: Spent Pd/C; Recovered palladium; Carbon monoxide oxidation; Moisture; Density functional theory EN Spent Pd/C Recovered palladium Carbon monoxide oxidation Moisture Density functional theory 1248 1248 1 03/08/21 20210305 NES 210305 B The Cover Feature b illustrates the use of green tea and NaBH SB 4 sb as agents for the reduction of a Pd/C catalyst for the efficient oxidation of CO. [Extracted from the article]

Over decades, nanozyme has served as a better replacement of bioenzymes and fulfills most of the shortcomings and intrinsic disadvantages of bioenzymes. Recently, manganese-based nanomaterials have been highly noticed for redox-modulated multienzyme mimicking activity and wide applications in biosensing and biomedical science. The redox-modulated multienzyme mimicking activity was highly in tune with their size, surface functionalization, and charge on the surface and phases. On the subject of calcination temperature to Mn 3 O 4 nanoparticles (NPs), its phase has been transformed to Mn 2 O 3 NPs and Mn 5 O 8 NPs upon different calcination temperatures. Assigning precise structure-property connections is made easier by preparing the various manganese oxides in a single step. The present study has focused on the variation of multienzyme mimicking activity with different phases of Mn 3 O 4 NPs, so that they can be equipped for multifunctional activity with greater potential. Herein, spherical Mn 3 O 4 NPs have been synthesized via a one-step coprecipitation method, and other phases are obtained by direct calcination. The calcination temperature varies to 100, 200, 400, and 600 °C and the corresponding manganese oxide NPs are named M-100, M-200, M-400, and M-600, respectively. The phase transformation and crystalline structure are evaluated by powder X-ray diffraction and selected-area electron diffraction analysis. The different surface morphologies are easily navigated by Fourier transform infrared, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy analysis. Fortunately, for the mixed valence state of Mn 3 O 4 NPs, all phases of manganese oxide NPs showed multienzyme mimicking activity including superoxide dismutase (SOD), catalase, oxidase (OD), and peroxidase; therefore, it offers a synergistic antioxidant ability to overexpose reactive oxygen species. Mn 3 O 4 NPs exhibited good SOD-like enzyme activity, which allowed it to effectively remove the active oxygen (O 2 •- ) from cigarette smoke. A sensitive colorimetric sensor with a low detection limit and a promising linear range has been designed to detect two isomeric phenolic pollutants, hydroquinone (H 2 Q) and catechol (CA), by utilizing optimized OD activity. The current probe has outstanding sensitivity and selectivity as well as the ability to visually detect two isomers with the unaided eye.

Non-invasive 3D imaging in materials and medical research involves methodologies such as X-ray imaging, MRI, fluorescence and optical coherence tomography, NIR absorption imaging, etc., providing global morphological/density/absorption changes of the hidden components. However, molecular information of such buried materials has been elusive. In this article we demonstrate observation of molecular structural information of materials hidden/buried in depth using Raman scattering. Typically, Raman spectroscopic observations are made at fixed collection angles, such as, 90°, 135°, and 180°, except in spatially offset Raman scattering (SORS) (only back scattering based collection of photons) and transmission techniques. Such specific collection angles restrict the observations of Raman signals either from or near the surface of the materials. Universal Multiple Angle Raman Spectroscopy (UMARS) presented here employs the principle of (a) penetration depth of photons and then diffuse propagation through non-absorbing media by multiple scattering and (b) detection of signals from all the observable angles.