Browsing by Author "Chandan Bhai Patel"

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Detection of a Neurotoxin Quinolinic Acid at Ultra-Trace Amount: SERS and DFT Study
(John Wiley and Sons Ltd, 2025) Monalisha Nayak; Chandan Bhai Patel; Om Prakash; Ashish Kumar Singh; Ranjan Kumar Singh
The presence of quinolinic acid (QA) below 100 nM is a normal condition while its increased amount may cause variety of neurodegenerative diseases. The precise detection of QA in trace amounts (nanomolar) is crucial to control its toxic effects. In the present study, the SERS-based detection of QA and its interaction at varying concentrations in human serum is carried out using silver nanoparticle substrates. The analysis of conformational dynamics of QA across different concentrations ranging from 10−3 to 10−9 M has been done. The adsorption mechanism between QA and silver nanoparticles has been studied using DFT, and the detection of QA up to nanomolar concentration is achieved. A significant shift in the SERS spectra of QA is observed between 10−4 and 10−5 M concentration, attributed to changes in adsorption geometry with varying pH and conformational change from zwitterionic QA → neutral QA. These findings are supported by UV–visible spectra, pH measurements, and DFT calculations. © 2025 John Wiley & Sons Ltd.
Diagnostic and prognostic application of Raman spectroscopy in carcinoma cervix: A biomolecular approach
(Elsevier B.V., 2021) Anju Shrivastava; Lalit Mohan Aggarwal; Chilakapati Murali Krishna; Satyajit Pradhan; Surendra Pratap Mishra; Sunil Choudhary; Chandan Bhai Patel; Saurav Singla; Ashish; Ranjan Kumar Singh
Blood serum samples from 63 cervical cancer patients and 30 controls were collected at three different phases of the treatment (i.e. before, during, and at follow up). The spectra of serum samples from control as well as patients were classified into different groups using principal component analysis (PCA) and linear discriminant analysis (LDA) based on different phases of treatment using R software. The spectra of blood serum samples have shown the distinct changes and differences compared with each other in the profile of various biochemical parameters. The sensitivity (92.5%) and specificity (85%) were observed maximum between control and cervical cancer patients (before treatment). Between different phases of treatment, the sensitivity and specificity were less but, all accuracies of detection and classification reached above 50%. This method can be considered as a screening method for detection and treatment monitoring. © 2020
Distinct spectral line shifts in the Raman lines’ Stokes and anti-Stokes components with temperature in the liquid crystalline system 4DBA
(Institute of Physics, 2025) Anoop Thomas; Chandan Bhai Patel; Ranjan K Singh; Kunwar Vikram
An anomalous Raman phenomenon (ARP) refers to a scenario in which the Stokes and anti-Stokes frequencies of a Raman mode are different. Here we report that ARP introduces different line shifts in Stokes and anti-Stokes frequencies in 4-Decyloxy Benzoic acid with temperature across two thermally driven structural transitions: the smectic (S) to nematic (N) phase transition at 375 K and the nematic (N) to isotropic (I) transition at 390 K. Four Raman modes near 663, 773, 1128, and 1168 cm−1 shift towards higher frequencies (blueshift) in the Stokes frequency and towards lower frequencies (redshift) in the anti-Stokes frequency with rise in temperature near S to N phase transitions. However, in the isotropic liquid phase, both the Stokes and anti-Stokes components exhibit a redshift as temperature increases, without any noticeable distinct spectral lineshifts. Our studies bring out the importance of phonon band structure in ARP. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Exploring a solid polymorphism and phase transitions in 4-cyano-4′-pentylbiphenyl (5CB) and rGO-doped 5CB using temperature dependent Raman spectroscopy
(Elsevier B.V., 2025) Ummer Bashir Khoja; Chandan Bhai Patel; Pankaj Kumar Tripathi; Rajesh Kumar; Soni Mishra; Sachin Kumar Singh; Ranjan Kumar Singh; Kunwar Vikram
Raman spectroscopy is used to examine the temperature-dependent phase transition behaviour of the liquid crystalline system 4-cyano-4′-pentylbiphenyl (5CB) and its nanocomposite with reduced graphene oxide (5CB@rGO) over the temperature range of −160 °C to 90 °C. First time, such a broad temperature range study of 5CB and 5CB@rGO has been reported. The structural and intermolecular interaction characteristics of the liquid crystal 5CB and its behaviour in the presence of reduced graphene oxide (rGO) are examined in depth by the temperature-induced Raman spectra and DFT calculations. To assess the phase transitions in 5CB and 5CB@rGO, the significant bands associated with the polar C[tbnd]N group and phenyl rings were thoroughly examined. A new crystal-crystal (solid polymorphism) phase transition is investigated first time, occurring between −120 °C and −100 °C. Another significant new crystal-crystal phase transition in 5CB and 5CB@rGO is also exposed, taking place between −20 °C and −10 °C. Differential scanning calorimeter (DSC) measurements confirm this new phase transition in 5CB and temperature sensitivity fairly matches Raman analysis. To evaluate the structural as well as change in intermolecular interactions in each phase, the detailed DFT study is performed on the 5CB molecule to establish the spectra-structure relation. The detailed spectra-structure correlation is discussed in this study. The spectra-structure correlation and change in spectral parameters are used to investigate the structure and intermolecular interaction of each phase. © 2025 Elsevier B.V.
Fabrication of Liquid Crystal Optical Sensors Using Cyclodextrin Polymer for Real Time, Selective and Visible Detection of Industrial Dyes in Contaminated Natural Water Samples
(Wiley-VCH Verlag, 2025) Madeeha Rashid; Satyabratt Pandey; Vishal Singh; Chandan Bhai Patel; Ranjan Kumar Singh; Sachin Kumar Singh
Industrial wastewater release of dyes poses serious environmental and health risks when introduced into natural water systems. Herein, a cyclodextrin-based polymer sensor (Ech-CDP) is developed for real-time, visible detection of harmful methylene blue (MB) and methyl orange (MO) dyes in distilled and contaminated natural water samples. The sensor works through a competitive host-guest mechanism between sodium dodecyl sulphate (SDS) and Ech-CDP, altering liquid crystal alignment. Initially, SDS induces homeotropic ordering, which shifts to a tilted state upon binding with Ech-CDP. The presence of MB or MO displaces SDS, reverting the alignment and causing a visible bright-to-dark transition under polarizers. The sensor exhibits high selectivity, with detection limits of 0.03 mM for MB and 0.05 mM for MO in aqueous solutions, and 0.08 mM for MB and 0.26 mM for MO in real water samples, remains effective for 3 days, and is unaffected by pH variations between 4.8 and 9.1. Additionally, the sensor demonstrates an on–off switching capability, suggesting potential applications for molecular logic gates and advancing environmental monitoring techniques in dye-polluted waters. © 2025 Wiley-VCH GmbH.
Investigation of phase transition in the binary mixture of thermotropic liquid crystalline systems 4-(Heptylox) benzoic acid and 4-(Undecyloxy) benzoic acid using Raman and DFT studies
(Elsevier B.V., 2023) Chandan Bhai Patel; K. Vikram; Pankaj Kumar Tripathi; Rajib Nandi; K. Ummer; Shashank Shekhar; Ranjana Singh; Ranjan K. Singh
A binary mixture Uba@Hba of liquid crystalline systems; 4-(Undecyloxy) benzoic acid and 4-(Heptylox) benzoic acid was prepared, and their liquid crystalline properties were investigated through differential scanning calorimetry and polarized optical microscopy at the bulk level and temperature dependent Raman spectroscopic technique as well as density functional calculations at molecular level. The polarized optical microscopic studies revealed crystal, smectic A, nematic and isotropic phases in the Uba@Hba. The phase transition temperatures of the binary mixture Uba@Hba was identified by the temperature dependent Raman study which was found almost close to phase transitions observed in differential scanning calorimetry and polarized optical microscopy. The detailed Raman & DFT studies provide information occurring in phase transitions at molecular level. The changes in inter/intra-molecular interactions at crystal → smectic A and smectic A → nematic transitions have been discussed in detail. © 2023 Elsevier B.V.
Monitoring the temperature-induced phase transition in a calamitic liquid crystal MABAB-12 via temperature-dependent Raman and DFT study
(Taylor and Francis Ltd., 2025) Sunny Shukla; Monalisha Nayak; Sachin Kumar Singh; Chandan Bhai Patel; Ranjan Kumar Singh
The calamitic liquid crystal methyl 4-(4’-12-alkoxybenzylideneamino) benzoate (MABAB-12) containing a Schiff base as linking group has been synthesised. Mesomorphic properties and phase transition temperatures were probed through temperature-dependent Raman spectroscopy and analysed using density functional theory (DFT). Analysis of Raman marker bands of C-H in-plane bending, C=C stretching of phenyl rings and C=N stretching of the linker gives evidence of phase transitions. To understand the molecular changes more clearly, an in situ Raman measurement of C-H in-plane bending has also been performed. The temperature-dependent Raman study of MABAB-12 reveals the intra-molecular rotation-induced coplanarity of phenyl rings during the Cr→SmA transition. As a result of intra-molecular rotation, significant charge transfer from the phenyl rings to the linking group is observed. Rotational conformational analysis of MABAB-12 has also been performed through density functional theory (DFT), which also supports induced coplanarity of phenyl rings at the Cr→SmA transition. The analysis of Raman spectra reveals the melting of the hitherto rigid core. © 2025 Informa UK Limited, trading as Taylor & Francis Group.
Probing the mesophase formation in thermotropic liquid crystal HBDBA using temperature-dependent Raman spectroscopy and DFT method
(Elsevier B.V., 2024) Chandan Bhai Patel; Satyabratt Pandey; Sachin K. Singh; K. Vikram; Ranjan K. Singh
Liquid crystalline properties of the synthesized liquid crystal (LC) N-(o-hydroxybenzylidene)-N′-(4-n-alkoxybenzylidene) azines (HBDBA) are probed thoroughly using the comprehensive array of techniques e.g. differential scanning calorimetry (DSC), differential thermal analysis (DTA), polarizing optical microscopy (POM), temperature-dependent Raman spectroscopy and density functional theory (DFT) method. In this study, intricate molecular interactions crucial for mesophase formation of liquid crystalline system HBDBA and molecular rearrangement that occurs during LC transitions are unravelled comprehensively. Remarkably, at the Cr → SmA phase transition, the peak position, linewidth, and intensity of signature Raman bands are prominently changed. A thorough analysis of Raman marker bands and DFT calculation confirm the disruption of intramolecular hydrogen bonds in HBDBA at the Cr → SmA transition. The conclusion of the present study enriches the understanding of the underlying mechanisms of mesophase formation and intricate molecular interactions and arrangement at the molecular level of the thermotropic LC. © 2024 Elsevier B.V.
Raman signature of the interaction between functionalized MWCNT and the liquid crystalline system (4DBA)
(American Institute of Physics, 2024) Ummer Bashir Khoja; Chandan Bhai Patel; Rajesh Srivastava; Vijay K. Mishra; Pankaj Tripathi; Amit Raj Singh; Ranjan K. Singh; K. Vikram
Liquid crystalline systems provide the best molecular matrix as a host for carbon nanotubes (CNTs) due to their fluidity character that controls the molecular ordering. The anisotropic shape of the CNTs makes them highly suitable nanoparticles that can be embedded in liquid crystalline systems to achieve uniform tunable dispersion. The uniform and stable dispersion of CNTs in the liquid crystalline host is challenging due to strong Vander Waal forces between CNTs. The functionalization of CNTs is one of the most popular techniques to achieve the dispersion system in an LC host due to the covalent bonding between CNT and LC systems. The COOH functionalized multi-wall carbon nanotubes (F-MWCNT) provide effective sites to interact with LC systems with the carboxylic group at the terminal. Raman spectroscopy is used as a probe to investigate the interaction between 4DBA and F-MWCNT through COOH - -COOH dimer formation. Comparative Raman analysis of 4DBA, 4DBA + bare MWCNT, and 4DBA + F-MWCNT spectra show bands associated with the COOH group giving strong evidence of interaction between 4DBA and F-MWCNT. Raman study reveals the mechanism of dimer formation between F-MWCNT and 4DBA. © 2024 Author(s).
Real-time optical detection of mercury contamination in drinking water using an amphiphilic recognition probe at liquid crystal/aqueous interfaces
(Royal Society of Chemistry, 2024) Satyabratt Pandey; Madeeha Rashid; Vishal Singh; Garima Singh; Chandan Bhai Patel; Rohit Verma; Dharm Dev; Ranjan Kumar Singh; Sachin Kumar Singh
Mercury contamination is a global environmental issue due to its toxicity and persistence in ecosystems. It poses a particular risk in aquatic systems, where it bioaccumulates and biomagnifies, leading to serious health impacts on humans. Therefore, effective detection technologies for mercuric ions in natural water resources are highly desirable. However, most existing detection methods are time-consuming, require complicated sample pre-treatment, and rely on expensive equipment, which hinders their widespread use in real-time detection. Here, we present a convenient, rapid, portable, user-friendly, and cost-effective sensing system for detecting Hg2+ ion contamination in water. This system utilizes a highly selective, amphiphilic, and structurally simple molecular probe, N-dodecylamine-di-thiocarbamate (DDC). DDC molecules align at the interface between the liquid crystal (LC) and water, inducing a homeotropic LC orientation. In water samples contaminated with Hg2+, a bright optical texture is observed, indicating the alignment of the 5CB LC in a planar manner at the LC/aqueous boundary. The minimum detectable concentration (LOD) for Hg2+ ions is 5.0 μM in distilled water, with a broad detection range from 5.0 μM to 2 mM. The sensor selectively detects Hg2+ ions over other common interfering metal ions, including Pb2+, Co2+, Ni2+, Cu2+, Cd2+, Zn2+, Cr2+, Mg2+, Na+, K+, and Ca2+. Boolean logic gates, bar graphs, and truth tables are employed to explain the selectivity of this liquid crystal-based sensor. This work demonstrates the significant potential of the sensor for monitoring mercuric ions in natural water resources, offering a promising strategy for controlling mercury pollution. © 2024 The Royal Society of Chemistry.
Spectroscopic study of coordination of Cu2+ with liquid crystal HBDBA: An investigation at ultra trace level
(Elsevier B.V., 2024) Chandan Bhai Patel; Monalisha Nayak; Satyabratt Pandey; Om Prakash; Sachin K. Singh; Ranjan K. Singh
The present work describes the synthesis and characterization of a copper complex with a liquid crystal compound called N-(o-hydroxybenzylidene)-N'-(4-n-alkoxybenzylidene) azines (HBDBA). The FTIR/ Raman spectroscopy and DFT calculations were employed to confirm the coordination of Cu2+ ion with HBDBA. On complex formation several changes in the Raman and FTIR spectra were observed. The linewidth and peak position of few Raman/ IR bands changed and few new bands in the Raman and IR spectra appeared. The experimentally observed bands of HBDBA molecule and its Cu2+- complex are assigned with the help of DFT. In the next part a concentration-dependent study has been done to detect ultra-trace amount (∼10–8 M) of Cu2+ ion binding with HBDBA using Raman and fluorescence spectroscopy. The result suggests that HBDBA can be used to detect Cu2+ ions in trace amount. © 2024
Temperature-Dependent Raman Spectroscopy Analysis of Epitaxially Grown Ge0.91Sn0.09 on GaAs (001) Substrate
(Pleiades Publishing, 2025) Dushyant Singh; Chandan Bhai Patel; Samir Ranjan Sahoo; Ranjan Kumar Singh; Rahul Kumar; Krista Roluahpuia Khiangte
Abstract: We report on the epitaxial growth of Ge0.91Sn0.09 alloy epilayers on a GaAs (001) substrate by low-temperature molecular beam epitaxy. Temperature-dependent Raman measurements were used to investigate the behavior and stability of Sn in Ge1–xSnx grown on GaAs by examining the behavior of the longitudinal optical phonon modes originating from both the Ge1–xSnx epilayers and the GaAs substrate. The Raman data reveals improved crystalline quality and increased Sn content in the Ge1–xSnx epilayer as the temperature is increased from 100 to 580 K. However, at a temperature of about T = 620 K, the mobility and segregation of Sn in the Ge1–xSnx epilayers dramatically increases. This behavior is similar to reports of Sn mobility and potential segregation from Ge1–xSnx grown on both Ge and Si substrates, despite differences in atom chemistry between Ge1–xSnx and the different substrates. Likely, the transition temperature for which Sn becomes mobile in Ge1–xSnx is dominated by its dependence on the bonding between Ge and Sn and level of strain in the Ge matrix. © Pleiades Publishing, Ltd. 2025.
Unveiling the Influence of Glutathione in Suppressing the Conversion of Aspirin to Salicylic Acid: A Fluorescence and DFT Study
(Springer, 2024) Monalisha Nayak; Chandan Bhai Patel; Anurag Mishra; Ranjana Singh; Ranjan K. Singh
Aspirin is a commonly used nonsteroidal anti-inflammatory drug, associated with many adverse effects. The adverse effects of aspirin such as tinnitus, Reye’s syndrome and gastrointestinal bleeding are caused due to conversion of aspirin into its active metabolite salicylic acid after oral intake. Glutathione is a naturally occurring antioxidant produced by the liver and nerve cells in the central nervous system. It helps to metabolize toxins, break down free radicles, and support immune function. This study aims to investigate and explore the possibility of inhibiting aspirin to salicylic acid conversion in presence of glutathione at a molecular level using spectroscopic techniques such as UV–Visible absorption, time-Resolved and time-dependent fluorescence and theoretical DFT/ TD-DFT calculations. The results of steady state fluorescence spectroscopy and time-dependent fluorescence indicated that the aspirin to salicylic acid conversion is considerably inhibited in presence of glutathione. Further, the results presented here might have significant clinical implications for individuals with variations in glutathione level. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.