Raman Spectroscopy Techniques Research Articles

Influence of nanosecond laser surface patterning on dental 3Y-TZP: Effects on the topography, hydrothermal degradation and cell response

ObjectivesLaser surface micropatterning of dental-grade zirconia (3Y-TZP) was explored with the objective of providing defined linear patterns capable of guiding bone-cell response. MethodsA nanosecond (ns-) laser was employed to fabricate microgrooves on the surface of 3Y-TZP discs, yielding three different groove periodicities (i.e., 30, 50 and 100 µm). The resulting topography and surface damage were characterized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). X-Ray diffraction (XRD) and Raman spectroscopy techniques were employed to assess the hydrothermal degradation resistance of the modified topographies. Preliminary biological studies were conducted to evaluate adhesion (6 h) of human mesenchymal stem cells (hMSC) to the patterns in terms of cell number and morphology. Finally, Staphylococcus aureus adhesion (4 h) to the microgrooves was investigated. ResultsThe surface analysis showed grooves of approximately 1.8 µm height that exhibited surface damage in the form of pile-up at the edge of the microgrooves, microcracks and cavities. Accelerated aging tests revealed a slight decrease of the hydrothermal degradation resistance after laser patterning, and the Raman mapping showed the presence of monoclinic phase heterogeneously distributed along the patterned surfaces. An increase of the hMSC area was identified on all the microgrooved surfaces, although only the 50 µm periodicity, which is closer to the cell size, significantly favored cell elongation and alignment along the grooves. A decrease in Staphylococcus aureus adhesion was observed on the investigated micropatterns. SignificanceThe study suggests that linear microgrooves of 50 µm periodicity may help in promoting hMSC adhesion and alignment, while reducing bacterial cell attachment.

Temperature-driven magnetic and structural transitions in multiferroic Lu(1-x)ScxFeO3

Novel metastable hexagonal Lu(1-x)SxFeO3 compounds were prepared by an ethylene glycol-based small molecule sol-gel synthesis route. Samples were investigated by means of XRD, Raman spectroscopy, XPS, SEM and magnetometry techniques. Based on the obtained data several different phase composition regions were discovered at room temperature depending on the Sc content. Three dominant phases were observed and denoted as the orthorhombic Pnma, hexagonal P63cm, and cubic Ia-3 with the hexagonal phase being stable without any additional phases when 0.40 ≤ x < 0.65. Temperature dependent structural analysis allowed for the construction of the phase diagram which revealed that upon increasing Sc content the reversible polar to non-polar phase transition temperature can be decreased from above 1200 °C (when x = 0.15) to around 800 °C (x = 0.75). SEM analysis indicated a rapid reduction in particle size from ∼2.726 µm when x = 0 down to ∼0.962 µm when x = 0.75, however in the case when x = 1, an increase in particle size was observed. XPS analysis confirmed the elemental composition and its changes as well as the stability of the 3 + oxidation state of the iron ions. Magnetization measurements confirmed a non-zero room temperature magnetization as well as the spin reorientation transitions whose critical temperatures TN increases from 156 K (x = 0.25) to 170 K (x = 0.75).

Structural, Magnetic, and Mössbauer Investigation of Mg-Ni-Co ferrites doped by Sm3+ sions

Samarium-doped magnesium-nickel-cobalt nanoferrites (Mg1/3 Ni1/3Co1/3)Fe2−xSmxO4, with x = 0.00, 0.01, 0.02, 0.04, and 0.08, were synthesized by the coprecipitation method. X-ray diffractometer (XRD), transmission electron microscopy (TEM), energy dispersive x-ray (EDX), x-ray photoelectric spectroscopy (XPS), Fourier Transform Infra-Red (FTIR), Raman spectroscopy, Mössbauer spectroscopy, and magnetic measurement techniques were used, to study the structure, microstructure, and magnetic properties of the samples. The formation of the cubic spinel structure was confirmed by Rietveld analysis of the XRD data and by the appearance of the two absorption bands close to 400 cm−1 and 600 cm−1 from the FTIR spectrum. Raman spectroscopy verified the formation of the spinel phase in the samples. The elemental composition, valency, and cationic distribution were examined using x-ray photoelectric spectroscopy (XPS) measurements. Experimental findings revealed that doping with Sm3+ ions had a significant effect on the magnetic properties of nanoparticles. The saturation magnetization (M s ) and coercivity field (H c ) values fluctuate depending on the crystallite size (DXRD) of the samples from XRD analysis as the Sm3+ content increases. The magnetization dependence on the applied field was investigated at different ranges of applied fields based on the output of the statistical parameters for the curve fitted using four different forms of the law of approach to saturation. The statistical parameters and physically significant fitted parameters give information on the dependence of magnetization over various applied field regions. A thorough investigation of the output parameters from fitting into various equations reveals that the composition of Mg-Ni-Co ferrites exhibits a dependence of magnetization on the applied field. Room-temperature Mössbauer spectra displayed a mix of the magnetic sextet and central quadrupole doublet, with improvement in the magnetic sextet in the Sm-doped samples. Moreover, Mössbauer spectra at 77 K showed the demise of the quadrupole doublet in all samples and showed two sextets (tetrahedral and octahedral sites). Sm-doping reduced the values of the hyperfine magnetic field of both sextets. All Fe ions can be found in the Fe3+ state, according to the isomer shift values and there is a migration of Fe3+ ions from octahedral to tetrahedral sites upon Sm doping, which was confirmed by XPS measurements.

Toxicity of Polystyrene Nanoplastics in the Liver and Intestine of Normal and High-Fat-Diet Juvenile Zebrafish.

Nanoplastics (NPs) are widely found and threaten environmental and biological safety, because they do not degrade completely. We aimed to preliminarily explore the toxicity of NPs in obese children, because childhood obesity is a growing global health concern. We used zebrafish as a vertebrate toxicological model to examine the hepatic lipid metabolism and gut microbiota in juvenile zebrafish exposed to 1000 μg/L polystyrene NPs and a high-fat diet (HFD) using Raman spectroscopy, pathological examination, transcriptome analysis, and 16S sequencing techniques. Our study showed that polystyrene NPs perturb the lipid metabolism and gut microbiota stability in zebrafish. Furthermore, the combined effects of polystyrene NPs and HFD resulted in gastrointestinal injury. Our study is one of the first to investigate the toxicity of polystyrene NPs to normal-diet and HFD juvenile zebrafish using confocal Raman spectroscopy. Our results show the importance of a healthy diet and a reduction in the use of plasticware. Environ Toxicol Chem 2024;43:147-158. © 2023 SETAC.

3D plasmonic hotspot engineering toward ultrasensitive and rapid EC-SERS recognition of plasticizers

Public attention to the health and environmental risks from plasticizer exposure in daily life has led to legal restrictions on the use of plasticizers in products. However, the lack of rapid, sensitive, and reliable analytic methods hinders the effective screening of toxic materials. In the present work, we propose a novel electrochemical surface-enhanced Raman spectroscopy (EC-SERS) technique for the detection of plasticizers such as phthalate esters (PAEs) and bisphenol A. The interior hotspots were realized through the EC deposition onto metal nanopillar (ECOMP) platforms in the presence of analytes within 2.5 min. The tiny molecules surrounded by Au produced sufficient amplification of SERS signals, leading to sub-parts-per-billion (sub-ppb) sensitivity for all the intended specimens. According to the three standard deviation equation, the limit of detection was determined to be 0.002 ppb. The ECOMP platforms with reproducibility (relative standard deviation of <10 %) and linear proportion (R2 ≥ 0.93) were highly suitable for reliable quantitative investigation. A principal component analysis method recognized their slight differences in spectral features. The variability from the first two components was achieved to be 73 %, which separated individual plasticizer groups distinctly. The plasticizer extracted from an actual polyvinyl chloride sample was successfully detected using the proposed technique. The interaction of PAEs with ethanol and the delocalization of PAEs in ECOMP platforms were also discussed. The results demonstrate the feasibility of plasticizer–ECOMP platforms being widely used for onsite testing in industrial fields such as chemical and drug safety.

Utilization of electrolytic manganese residue and bauxite to synthesize zeolite a for pickle liquor adsorption: Characterization, mechanisms and performance

Electrolytic manganese residue (EMR) and its pickle liquor are extremely hazardous wastes that can cause significant environmental and biological hazards. In order to solve these problems, this paper used EMR and bauxite (BA) as the main raw materials to synthesize zeolite A (EMRZ), and carried out adsorption and purification of pickle liquor so as to realize the comprehensive utilization of EMR and BA. The study investigated the optimal parameters for the synthesis of zeolite and subsequently characterized the synthesized EMRZ. The characterization results revealed that the synthesized EMRZ exhibited notable attributes such as high purity, high crystallinity, and exceptional ion exchange capabilities. Subsequently, the synthesis mechanism of EMRZ was elucidated using XRD, FTIR, Raman spectroscopy, and MAS NMR techniques. The growth process of EMRZ involved three distinct stages, namely the growth induction period, rapid growth phase, and growth completion stage. More specifically, the transformation sequence was observed as follows: double four-membered rings (D4R) → β cages → α cages → zeolite A crystals. Besides, the migration and transformation of Si and Al in EMR were explored, and the mechanism was further expounded. In addition, the synthesis of EMRZ has been evaluated economically and compared with other zeolites synthesized by different methods. It was discovered that EMRZ has a higher economic value. Moreover, an investigation was conducted on the adsorption effect of EMRZ on impurity ions present in pickle liquor. It was discovered to be effective at removing impurity ions, suggesting that EMRZ is a feasible purification material for pickle liquor. Furthermore, the adsorption mechanism was ion exchange between impurity ions and Na ions, and EMRZ was successfully regenerated. The findings of the study validate the potential of EMRZ as a highly effective adsorbent for the treatment of pickle liquor, thereby offering a viable approach for the comprehensive utilization of EMR.

Pressure dependence on Raman spectra of the molecular crystal 4-(benzenesulfonyl)-morpholine

The structural and vibrational properties of 4-(benzenesulfonyl)-morpholine, C10H13NO3S, have been studied using multinuclear (1H and 13C) NMR, IR and Raman spectroscopy techniques at pressures up to 3.2 GPa, as well as molecular modeling and vibrational mode assignment using DFT calculations with B3LYP functional and 6-31G (d,p) basis set and potential energy distribution (PED). Experimental and calculated spectra were compared and showed good accuracy. The sample was subjected to high pressure in the range of 0 to 3.2 GPa. The pressure measurements suggest a conformational transition for values around 0.7, 1.7 and 2.5 GPa, which was observed in some spectral regions, mainly in the high energy vibrational bands.

Synthesis of water-soluble nitrogen doped carbon quantum dots-polypyrrole nanocomposite via in-situ polymerization for high performance supercapacitor application

In this work, water-soluble nitrogen doped carbon quantum dots (NCQDs) were synthesized via a hydrothermal approach, and nitrogen doped carbon quantum dots-polypyrrole nanocomposites (NCQDs/PPy) were synthesized using In-Situ chemical polymerization methods. The synthesized pure NCQDs, PPy, and NCQDs/PPy nanocomposites are characterized with help of X-ray diffractometry (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscope (FESEM), Ultraviolet-Visible (UV–Vis) spectroscopy, and Raman spectroscopy techniques to study their chemical changes, structural phase, morphology, and optical properties. The electrochemical performance is investigated through a two-electrode system, and the NCQDs/PPy-2 nanocomposite shows a high specific capacitance (Csp) of 750 Fg−1 at a current density (CD) of 1 Ag−1 with a wide operating potential window from −0.8 V to 0.8 V. In addition, the fabricated symmetrical device shows an energy density (ED) of 43.47 Whkg−1 and a high-power density (PD) of 3129.84 Wkg−1. Besides, the NCQDs/PPy-2 shows a higher cycle life span with 77.82 % of capacitance retention and 97.04 % of coulombic efficiency even after 8000 charging and discharging cycles. These findings demonstrate that NCQDs/PPy-2 nanocomposite material is a highly prominent electrode material for supercapacitor applications.

Understanding ageing mechanism of carbon electrodes in double layer capacitors operating in organic electrolytes

Understanding the ageing mechanisms of porous carbon electrodes used in electrochemical double layers supercapacitors (EDLCs) is of high importance to improve their lifetime. In this work, we studied ageing of two different porous carbons with different pore size distribution and surface functionalities in 1.5 M tetraethyl ammonium tetrafluoroborate (Et4NBF4) in acetonitrile (AN) electrolyte. The combination of Raman spectroscopy, thermogravimetric analysis (TGA), gas sorption and electrochemical impedance spectroscopy techniques allowed us to identify two different behaviors depending on the porous carbon used. A microporous carbon experiences an ionic/electronic resistance increase leading to a capacitance fall off upon cycling, associated with pore clogging. This resulted from the electrolyte degradation taking place at the positive electrode combined with porous carbon oxidation. Differently, only an increase of the series resistance was observed for the mesoporous carbon tested, following the creation of defects at the positive carbon electrode.

Niobium and carbon nanostructured coatings for corrosion protection of the 316L stainless steel

This work aims to investigate the influence of niobium and carbon nanostructured coatings on the corrosion resistance of the 316L SS. The coated and uncoated specimens were morphologically and structurally characterized by using OM, SEM/EDX, DRX, FTIR, Raman spectroscopy and XPS techniques. The corrosion behaviour was assessed by OCP, PPc, EIS as well as immersion tests in 0.6 mol L−1 NaCl solution. In addition, the average contact angles were used to evaluate the surfaces free energy by the Van Oss interfacial tension component theory approach. Results showed that the surface treatments positively influenced the corrosion resistance of the 316L SS and the coatings act as a protective barrier against corrosion process. The reactive sputtering technique increased the wettability of the surfaces in relation to the base material. Considering applications in aggressive media, the 316L SS/Nb2O5 specimen exhibits superior performance when compared to the base material and 316L SS/carbon.

Rapid Detection of SARS-CoV-2 in Clinical and Environmental Samples via a Resonant Cavity SERS Platform within 20 min.

The coronavirus disease 2019 (COVID-19) epidemic has given a warning that it is important to explore the rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in clinical specimens or environmental samples for public health strategies and future variants. The surface-enhanced Raman spectroscopy (SERS) technique was demonstrated to achieve this goal. However, the consistency of signals originating from the poor compatibility of virions with SERS hotspots remains a key scientific challenge for the practical applications of SERS. Herein, we develop a SERS platform for the ultrasensitive and rapid detection of SARS-CoV-2 antigen within 20 min by the combination of a highly consistent SERS substrate and a supervised deep learning algorithm. A V-shaped resonant cavity array (VRC) substrate was fabricated to trap SARS-CoV-2 virions in the periodic V cavity array and stimulate the integral SERS signal of the virus via a resonance coupling effect. Benefiting from the unique architecture of the VRC substrate, we were able to directly detect the SARS-CoV-2 virus with high sensitivity and high consistency. These excellent performances enabled us to identify five different kinds of SARS-CoV-2 variants and detect SARS-CoV-2 from clinical and environmental samples with high accuracies.

Diffuse Reflectance-Based Femtosecond Stimulated Raman Spectroscopy of Opaque Suspensions.

By augmentation of the collection optics utilized in transmission-based femtosecond stimulated Raman spectroscopy (FSRS), two novel diffuse reflectance-based femtosecond stimulated Raman spectroscopy (drFSRS) techniques were developed. These techniques were then used to collect the Raman spectra of opaque systems, those being cyclohexane-intercalated poly(tetrafluoroethylene) microbeads and ethanol in 1% intralipid solutions. The resulting drFSRS data from the cyclohexane:PTFE system show significant distortion of the depolarization ratio of the 803 cm-1 cyclohexane peak, indicating a loss of incident pump:probe polarization in a scattering environment. The drFSRS data from the ethanol in 1% intralipid solution demonstrate less signal strength but equal spectral resolution when compared to transmission-based FSRS of the same sample. The results presented in this Technical Note demonstrate the current capabilities of collecting stimulated Raman spectra of opaque systems using drFSRS.

Practical mechanochemical synthesis and electrochemical properties of Mn3O4 for use in supercapacitors

A facile method to synthesize Mn3O4 crystalline powders for use in supercapacitor electrodes is reported. Specifically, the mechanochemical synthesis was carried out with high-energy ball milling and a short milling time of 1 h. The physicochemical properties of the resultant powders were characterized by XRD, Raman spectroscopy, SEM, and N2 adsorption-desorption techniques. In addition, the electrochemical capabilities were tested in two different configurations: a three-electrode cell, and a symmetric supercapacitor (SSC) with a two-electrode arrangement. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge were applied to the samples with both configurations. The Mn3O4 samples were synthesized from manganese chloride tetrahydrate and sodium peroxide with two molar ratios, 1:1 and 1:1.5. The samples showed excellent electrochemical stabilities of 99.7 % after 5000 charge-discharge cycles, and the highest electrochemical capacitance of 485 F·g1 at 5 mV s1 was observed for the sample prepared with a 1:1 ratio of reagents and used with the three-electrode configuration.

Raman Spectroscopy as a Potential Adjunct of Thyroid Nodule Evaluation: A Systematic Review.

The incidence of thyroid nodules (TNs) is estimated at 36.5% and 23% in females and males, respectively. A single thyroid nodule is usually detected during ultrasound assessment in patients with symptoms of thyroid dysfunction or neck mass. TNs are classified as benign tumours (non-malignant hyperplasia), benign neoplasms (e.g., adenoma, a non-invasive follicular tumour with papillary nuclear features) or malignant carcinomas (follicular cell-derived or C-cell derived). The differential diagnosis is based on fine-needle aspiration biopsies and cytological assessment (which is burdened with the bias of subjectivity). Raman spectroscopy (RS) is a laser-based, semiquantitative technique which shows for oscillations of many chemical groups in one label-free measurement. RS, through the assessment of chemical content, gives insight into tissue state which, in turn, allows for the differentiation of disease on the basis of spectral characteristics. The purpose of this study was to report if RS could be useful in the differential diagnosis of TN. The Web of Science, PubMed, and Scopus were searched from the beginning of the databases up to the end of June 2023. Two investigators independently screened key data using the terms "Raman spectroscopy" and "thyroid". From the 4046 records found initially, we identified 19 studies addressing the differential diagnosis of TNs applying the RS technique. The lasers used included 532, 633, 785, 830, and 1064 nm lines. The thyroid RS investigations were performed at the cellular and/or tissue level, as well as in serum samples. The accuracy of papillary thyroid carcinoma detection is approx. 90%. Furthermore, medullary, and follicular thyroid carcinoma can be detected with up to 100% accuracy. These results might be biased with low numbers of cases in some research and overfitting of models as well as the reference method. The main biochemical changes one can observe in malignancies are as follows: increase of protein, amino acids (like phenylalanine, tyrosine, and tryptophan), and nucleic acid content in comparison with non-malignant TNs. Herein, we present a review of the literature on the application of RS in the differential diagnosis of TNs. This technique seems to have powerful application potential in thyroid tumour diagnosis.

Trimetallic CuO/Ag/NiO supported with silica nanoparticles based composite materials for green hydrogen production

Production and utilization of grey and blue hydrogen is responsible for emission of millions of tons of carbon dioxide (CO2) across the globe. This increased emission of CO2 has severe repercussions on the planet earth and in particular on climate change. Here in, we explored advance bimetallic (BM) CuO/Ag and trimetallic (TM) CuO/Ag/NiO based nanoporous materials supported with silica nanoparticles (SiNPs) via sol–gel route. The explored nanocatalysts were characterized by Powder X-ray diffraction (P-XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopic techniques. These advance nanocatalysts were evaluated for the green hydrogen production through electrocatalysis and photocatalysis. The catalysts exhibited an exceptional catalytic performance, the onset potential for hydrogen evolution reaction (HER) was determined to be − 0.9 V BMSiNPs-GCE and − 0.7 V (vs Ag/AgCl) for TMSiNPs-GCE, whereas η@10 for BMSiNPs-GCE and TMSiNPs-GCE is − 1.26 and − 1.00 V respectively. Significantly, the TMSiNPs composite and the BMSiNPs composite exhibited superior photochemical H2 evolution rates of 1970.72 mmol h−1 g−1 and 1513.97 mmol h−1 g−1, respectively. The TMSiNPs catalyst presents a highly promising material for HER. This study reveals a cost-effective approach to develop sustainable and resourceful electrocatalysts for HER.

In-situ deposition of silver nanoparticles on cuprous oxide hollow spheres for sensitive and recyclable SERS sensing in solution based on electromagnetic and chemical enhancement

In order to achieve widespread application of surface-enhanced Raman spectroscopy (SERS) technique for practical sensing illegal additives in food, it is crucial to construct a reliable SERS substrate that offers both high sensitivity and reusability. This work utilized a simple and rapid in-situ deposition method to deposit Ag nanoparticles onto hollow Cu2O nanospheres, resulting in the formation of Cu2O/Ag nanocomposites with photocatalytic and SERS properties. These nanocomposites were employed as a hopeful SERS analysis for effective sensing of colorant additives in fruit juice, including methylene blue (MB) and rhodamine 6G (R6G). Impressively, the nanocomposites exhibited an exceptional detection limit of 10−9 M for the color agents and demonstrated a strong linear relationship between SERS intensities and the logarithmic concentration (R2 ≥ 0.95). The hollow structure of Cu2O provided low density and long-term dispersion stability in solution, which are beneficial for real-time monitoring the additives in liquid food. The excellent SERS performance can be attributed to the electromagnetic effect of Ag metals and the chemical enhancement of Cu2O semiconductors, as confirmed by the N 1 s XPS spectra from MB. Furthermore, the Cu2O/Ag nanocomposites efficiently degraded dye molecules under UV light irradiation within a short period of 45 min. So, the nanocomposites exhibited practical recyclability, as demonstrated by their consistent performance over five cycles of SERS sensing. These findings highlight their significant potent for SERS sensing trace pollutants and ecological restoration by photocatalytic reaction in the future.

Ultrafast photodegradation of methylene blue dye and supercapacitor applications of flower like hydrothermal synthesized V2O5 nano -structures on rGO as nano - composite

In recent years, studies into the energy storage and water remediation are on the top priority of material scientists. Development of graphene-based materials for the purpose is a novel attempt in current research. Novel rGO - V2O5 nano composite having excellent photocatalytic and supercapacitor properties was designed and characterized in the present manuscript. V2O5, reduced graphene oxide (rGO) and rGO-V2O5 composite (with concentrations 1:0.5, 1:1, 1:2, and 1:3), were synthesized by hydrothermal method, standard modified Hummer's method followed by Hydrazine based reduction and sonochemical method, respectively. All the compounds were characterized by X-ray diffraction (XRD), Raman spectroscopy and Scanning Electron Microscopic techniques to study the structural and morphological aspects. Photocatalytic dye degradation experiments for Methylene Blue dye degradation and Electrochemical studies including cyclic voltammogram (CV), Galvanostatic Charging and Discharging (GCD), Electrochemical Impedance Analysis (EIS) experiments were performed on these compounds. XRD and Raman studies confirm the successful synthesis of these compounds and SEM images manifest excellent distribution of nano V2O5 on rGO sheets. At the concentration of 1:1, the rGO-V2O5 composite exhibits an ultrafast degradation of MB up to 94% under visible irradiations in just 8 min because of its narrow bandgap (2.4 eV) compared to the bare rGO (51%@135) and V2O5 (15%@22), respectively. Trapping-active-species experiment was performed to understand the MB degradation mechanism with rGO-V2O5, where the superoxide ion role has been found to be superior to other elements present in the degradation reaction. The optimized rGO-V2O5 (1:1) composite was further employed in the supercapacitors, showing a higher specific capacitance (Cs) of 818 F/g than that of the bare rGO (548 F/g) and V2O5 (246 F/g) at the 1 A/g of current density in 3 M KOH aqueous electrolytes. The results manifest ultrafast degradation and superior electrochemical performance for the designed composite of rGO and V2O5.

A prospective study: Advances in chaotic characteristics of serum Raman spectroscopy in the field of assisted diagnosis of disease

Chaos theory is an important branch of mathematics and its theory has been widely applied in many fields such as physics and medicine. Based on existing spectroscopic techniques, this paper used chaos theory as a research method for nonlinear time series to analyze Raman spectral time domain curves in order to improve the performance of disease diagnostic models and explore a new paradigm of spectroscopic technology for intelligent assisted disease diagnosis. We quantitatively identified the chaotic characteristics of time domain Raman spectra by three methods, extracted chaotic features such as correlation dimension and Kolmogorov entropy, and used the chaotic features as input to Extreme Learning Machine (ELM), Back Propagation Neural Network (BPNN), K-Nearest Neighbor (KNN) and Support Vector Machine (SVM) to diagnose patients with lung cancer (LC), glioma, renal cell carcinoma (RCC) and esophageal cancer (EC). The Raman spectra were also analyzed by traditional spectral feature extraction & modelling method, and the results of traditional spectral feature extraction & modelling method and chaotic feature modelling method were compared. The experimental results showed that the extraction of effective chaotic features in the full spectral range could achieve comparable diagnostic results with the traditional spectral feature extraction & modelling method. To further validate the effectiveness of chaos theory in Raman spectral data, the full spectrum was divided into three consecutive subsequences of 500–1000, 1000–1500, and 1500–2000 cm−1, and the above experimental steps were repeated respectively, and the results of the traditional spectral feature extraction & modelling method and chaotic feature modelling were compared. The results showed that as the spectral range was split into consecutive subsequences, the diagnostic performance of the chaotic features in each subsequence performed better than that of conventional spectral analysis techniques. In this study, the technique bridges the gap in the application of chaotic signals to Raman spectroscopy techniques, focuses on global features in the time domain profile of Raman spectra, and demonstrates the significant value of chaos theory in artificial intelligence-assisted spectroscopic medical diagnosis.

Platinum nanoparticle-decorated reduced graphene oxide nanosheets: A recyclable and highly efficient catalyst towards the reduction of para-nitrophenol and methylene blue

The present study focuses on the design and development of Pt nanoparticle (PtNPs) decorated reduced graphene oxide (RGO) nanohybrid as an efficient heterogeneous catalyst towards the reduction of p-nitrophenol (p-NP) and methylene blue (MB). The citrate reduction of chloroplatinic acid in the presence of amino-propyl trimethoxy silane (APTMS) modified graphene oxide (GO) produced RGO/PtNPs nanohybrid comprised of uniform and high-density distribution of smaller-sized PtNPs. The APTMS provide efficient nucleation points via their amino groups and thereby play a vital role in regulating the size as well as the distribution of the anchored PtNPs in the present approach. The morphological and structural characterization of RGO/PtNPs nanohybrid was done by using X-ray powder diffraction, scanning and transmission electron microscopy, Fourier transform infrared and Raman spectroscopic techniques. The homogeneous and high-density dispersion of smaller-sized PtNPs endows superior catalytic activity to RGO/PtNPs nanohybrid. The nanohybrid exhibited outstanding catalytic performance enabling rapid reduction of both p-NP and MB at ambient conditions. The estimated rate constants for p-NP and MB reduction were 15.9 × 10−3, and 187 × 10−3 s−1 respectively, which outperform the rate constants of several previously reported metal-based GO/RGO nanocatalysts. The recycling tests showed that the nanohybrid maintained good catalytic stability even after the fifth recycle run. The RGO/PtNPs nanohybrid can be exploited for sustainable and efficient catalytic reduction of other environmental pollutants also. Further, the strategy followed in the present study to achieve homogenous and high-density distribution of Pt nanoparticles could be adopted for the anchoring of other metal/metal oxide/semiconductor nanoparticles.

Ag-based magnetic metal organic framework nanocomposite as catalyst for nitrophenol removal

In this work a silver based Magnetic Metal Organic Framework Nanocomposite (MMOFC) was prepared in which nanoparticles of magnetic iron oxide and nano Ag MOF of Ag-Benzene tricarboxylic acid form a nanostructure (IO@Ag-BTC). The synthesized nanostructure was characterized using XRD, SEM, EDS, TEM, TGA, IR and Raman spectroscopic techniques. The optical and morphological characterization confirmed the formation of a large number of low-symmetry spherical shaped particles of size ∼53 nm together with some rod-like shapes with aspect ratio ranging from 3.7 to 11.23. The potential of the synthesized IO@Ag-BTC MMOFCs towards the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was demonstrated.