Browsing by Author "Ranjan Kumar Singh"

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Assessment of solution stability and drug release properties of liposomal curcumin in peritoneal dialysis fluid and its synergistic antibacterial activity with vancomycin
(Elsevier B.V., 2022) Pranjali Pranjali; Ritu Raj; Khushboo Rani Singh; Narayan Prasad; Ranjan Kumar Singh; Krishna Mohan Poluri; Dinesh Kumar; Anupam Guleria
Infectious Peritonitis associated with recurrent and persistent infections is the major cause of technique failure of life-sustaining peritoneal dialysis (PD) therapy used for treating patients with end-stage renal failure (ESRF). The infections -if diagnosed timely- are usually resolved with empiric antibiotic treatment. However, the treatment of infections associated with drug resistant bacteria or fungal infections remains challenging, poses a very serious problem to the health of PD patients, and is the leading cause of mortality and morbidity. Therefore, the development of alternate approaches other than antibiotics are required to keep up with the constantly changing and increasing multiple drug resistance (MDR) of bacterial strains. Curcumin exhibits anti-oxidative/anti-inflammatory potential and remarkable wound healing properties. It also has broad-spectrum anti-bacterial/anti-biofilm effects and its synergistic antibacterial activity with several antibiotics (including those used clinically for the treatment of PD associated infections) is well proven against variety of pathogenic infections including MDR strains. However, poor water-solubility of curcumin (<0.125 mg/L) remains a major barrier to achieve desirable bioavailability and further limit its therapeutic efficacy. Among the various drug carrier strategies, liposomal encapsulation has been found to be most promising mode to remarkably enhance the therapeutic index of curcumin by facilitating its gastric absorption, protecting its enzymatic degradation and allowing its slow release over time for maximum benefits. However, to date, the potential of liposomal curcumin has not been explored for the treatment of PD associated infections. Starting our efforts in this direction, a comprehensive assessment of solution stability and drug release properties of curcumin-loaded liposomal vesicles has been demonstrated in peritoneal dialysis fluid. The results clearly indicated an excellent solution stability of curcumin loaded inside liposome and the formulation affirms the regulated curcumin release enhancing the bioavailability. Further, we evaluated the synergistic antibacterial efficacy of curcumin-loaded liposomal formulation with vancomycin against the Staphylococcus aureus and Escherichia coli – pathogens (known for causing intra-peritoneal infections during PD). This synergy strategy resulted in outstanding improvement in bacterial inhibition efficacy of liposomal curcumin at significantly lowered doses. The results of the present study propose lipocurcumin as a potent antibiotic additive to vancomycin to cure PD-infections caused by antibiotic-resistant bacteria. © 2022
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
Effect of Aegle marmelos leaf extract on N-methyl N-nitrosourea-induced hepatocarcinogensis in Balb/c mice
(2013) Shalini Verma; Theeshan Bahorun; Ranjan Kumar Singh; Okezie I. Aruoma; Arvind Kumar
Context and objective: Tobacco smoke and nitrostable foods containing N-methyl N-nitrosourea (MNU) are among the primary causes of liver cancer. To substantiate the beneficial claims ascribed to Aegle marmelos (L.) Corrêa (Rutaceae), the hepatoprotective potential of its leaf extract was studied using an MNU-induced hepatocarcinogenesis model in Balb/c mice. Materials and methods: After dose selection, 40 mice were randomly assigned to 4 groups: I (control), II (intraperitoneally (i.p.) primed with 50 mg/kg MNU), III (100 mg/kg A. marmelos hydroalcoholic extract (HEAM) i.p.) and IV (MNU + HEAM, i.p.). Inflammatory (IL-1β, IL-6), anti-inflammatory (IL-4) cytokine expression, apoptosis (Bcl-2) and tumor-related (p53, c-jun) genes were assessed at mRNA level. HEAM effects on hematological parameters were examined. Results and discussion: HEAM treatment decreased IL-1β, IL-6, Bcl-2 and c-jun respectively expressions by 90, 25, 53 and 30%, respectively. p53 and IL-4 expression was up-regulated by 1.5- and 2-fold. MNU decreased hemoglobin concentration (25%), lymphocyte count (42%) and increased leukocyte (100%), platelet (4-fold), neutrophil (43%), monocyte (10-fold) and eosinophil (10-fold) counts in Group II mice while HEAM modulated the same parameters by -7%, -21%, +24%, +3-fold, +12%, +3-fold and +4-fold, respectively, in MNU-induced mice compared to control. HEAM protective effect was confirmed by Raman spectroscopy where the MNU-induced peak at 1252 cm-1 was normalized. DNA fragmentation data suggest apoptosis as one of the protective mechanisms of HEAM. Conclusion: The hepatoprotective, anti-carcinogenic and immunomodulatory effects of A. marmelos extract indicate potential beneficial effects in cancer therapy. © 2013 Informa Healthcare USA, Inc. All rights 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.
Fermented papaya preparation modulates the progression of N-methyl-N-nitrosourea induced hepatocellular carcinoma in Balb/c mice
(Elsevier Inc., 2016) Jhoti Somanah; Srishti Ramsaha; Shalini Verma; Ashok Kumar; Poornima Sharma; Ranjan Kumar Singh; Okezie I. Aruoma; Emmanuel Bourdon; Theeshan Bahorun
Aim and main method The medicinal properties of fermented papaya preparation (FPP) derived from Carica papaya fruit was investigated in order to determine its ability to modulate the progression of N-methyl-N-nitrosourea induced hepatocellular carcinoma in Balb/c mice. Key findings As well as reducing the physical symptoms associated with N-methyl-N-nitrosourea (MNU)-induced hepatocellular carcinoma, supplementation of Balb/c mice with 500 mg FPP/kg BW for 92 days normalized the blood cell count, led to an increased activity of several key antioxidant enzymes (SOD: + 20%, CAT: + 81%, GPx: + 66.1%, GR: + 54.4%; P < 0.001 vs. MNU control), increased the ferrous reducing antioxidant potential (+ 36.7%, P < 0.001 vs. MNU control) and reduced the extent of lipid peroxidation in the liver by 44.3% (P < 0.001 vs. MNU control). Significance Results demonstrated the ability of FPP to preserve the integrity of liver against oxidative damage and protect hepatocytes against irreversible DNA structural modifications induced by MNU, highlighting its potential role as an immune-defense modulator during hepatocarcinoma. © 2016 Elsevier Inc.
In vitro and ex vivo relaxometric properties of ethylene glycol coated gadolinium oxide nanoparticles for potential use as contrast agents in magnetic resonance imaging
(American Institute of Physics Inc., 2020) Anamika Chaturvedi; Pranjali Pranjali; Mukesh Kumar Meher; Ritu Raj; Madhuri Basak; Ranjan Kumar Singh; Krishna Mohan Poluri; Dinesh Kumar; Anupam Guleria
Magnetic nanoparticles (MNPs) have widely demonstrated their applicability in many biomedical applications including magnetic resonance imaging (MRI), hyperthermia, and drug delivery. However, the effectiveness of MNPs can be limited for in vivo applications due to their hydrophobic surfaces leading to nanoparticle agglomeration and thus requires appropriate surface modification to enhance colloidal stability. Glycols are widely used coating material for surface modifications of MNPs to improve their physicochemical properties and biocompatibility. The present work reports the preparation of two different sized ethylene glycol coated gadolinium oxide nanoparticles (EG@Gd2O3 NPs) using two different synthesis approaches and their applicability as contrast agents in MRI. Thermo-gravimetric analysis and Fourier transform infrared spectroscopy confirmed the successful coating of ethylene glycol on the surface of NPs. We found that independent of the size of NPs, the globular shaped EG@Gd2O3 NPs exhibited similar crystal structures, magnetic properties, and cellular cytotoxicity behavior. However, a significant impact of size on MRI contrast enhancement properties was seen. It was revealed that the relaxivity of EG@Gd2O3 NPs increases with a decrease in particle size. Small sized EG@Gd2O3 NPs (∼12 nm) exhibited a high specific in vitro and ex vivo longitudinal relaxivity of 3.7 and 1.5 mM-1 s-1, respectively, thus clearly elucidating the potential of these NPs for use as local contrast enhancement agents. The present study gives insights into the intrinsic dependence of magnetic resonance contrast effects of NPs on particle size and surface coating layer mass ratio and thus demonstrates the development of efficient magnetic nanoparticles based contrast agents by fine tuning of particle size and surface properties. © 2020 Author(s).
Inhibition Conversion of Aspirin into Salicylic Acid in Presence of Glycine
(Springer, 2025) Richa A. Singh; Manish Kumar Tiwari; Ranjan Kumar Singh
Aspirin (AS) is a common drug having anti-pyretic and anti-inflammatory properties which is widely used in diverse medical conditions. The intake of AS may cause adverse effects such as gastrointestinal ulcer, tinnitus and Reye’s syndrome. The adverse effects of AS arise due to conversion of AS into salicylic acid (SAL). Glycine (Gly) is a simplest non essential amino acid having anti-oxidative and anti-inflammatory effects. It also reduces the risk of obesity, hypertension, and diabetes mellitus. AS with Gly is well accepted form of the drug for the treatment of rheumatic conditions in comparisons to the bare AS. In the present work using UV-Visible absorption, fluorescence and DFT/ TD-DFT techniques confirmed that in presence of Gly inhibited the conversion of AS into SAL effectively. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
Investigation of magnetic resonance contrast properties of PEG-coated gadolinium oxide nanoparticles in various biological environments
(Institute of Physics, 2024) Anamika Chaturvedi; Pranjali Pranjali; Ritu Raj; Ayush Shukla; Ranjana Singh; Deepak Kumar Tripathi; Krishna Mohan Poluri; Ranjan Kumar Singh; Dinesh Kumar; Anupam Guleria
Magnetic nanoparticles (MNPs) are promising tools for biomedical applications, particularly in molecular imaging using magnetic resonance imaging (MRI). The unique magnetic properties of MNPs, combined with their similarity in size to biological objects, make them ideal candidates for in situ imaging probes. The present study explores the use of magnetic nanoparticles (MNPs) as contrast agents in magnetic resonance imaging (MRI) for improved diagnostic accuracy. Specifically, the study investigates the MR contrast properties of polyethylene glycol-coated gadolinium oxide nanoparticles (PEG@GONPs) in five different biological fluids. The nanoparticles were synthesized using the polyol route and their size, shape, and morphology were characterized using TEM, SEM, and FT-IR spectroscopy. The magnetic resonance (MR) relaxivity of PEG@GONPs was studied in different biologically relevant media, and results revealed highest relaxivity in plasma as compared to other media. In addition, comparative analysis of proton relaxivity of the synthesized nanoparticles was carried out with a well-known gadolinium-based contrast agent, Omniscan, in various medium. The present findings revealed that PEG@GONPs can serve as an effective contrast agent for MRI imaging in biological fluids such as plasma, which is crucial for preclinical diagnosis of specific diseases and lesions. The high relaxivity observed in plasma could be attributed to the interaction of the nanoparticles with plasma proteins, amplifying their magnetic properties which further improve their ability to produce contrast in MR images. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Investigations on structural and optical properties of ZnO and ZnO:Co nanoparticles under dense electronic excitations
(Royal Society of Chemistry, 2014) Shiv Kumar; Kandasami Asokan; Ranjan Kumar Singh; Sandip Chatterjee; Dinakar Kanjilal; Anup Kumar Ghosh
In the present study, the structural, morphological, and optical properties of Co-doped ZnO nanoparticles (NPs) prepared by a sol-gel method before and after dense electronic excitations caused by swift heavy ion irradiation have been reported. The pristine and ZnO:Co NPs were irradiated by using a 200 MeV Ag15+ ion beam at a fluence of 5 × 1012 ions per cm2. Structural characterization has been performed using X-ray diffraction (XRD) with Rietveld refinement. It shows that the samples are of single phase; grain size and tensile strain has been increased in the ion-irradiated samples. Room temperature Raman spectroscopy measurements show that microscopic structural disorders reduce the translational symmetry giving rise to local distortions in the lattice. Atomic force microscopic (AFM) studies show prominent grain boundaries and suggest that roughness of the irradiated surfaces increases strongly compared to their pristine counterparts. Optical absorption and photoluminescence (PL) studies also reflect the dopant incorporation and swift heavy ion (SHI) irradiation effect on the nanoparticles. UV-Vis absorption measurement has been utilized to estimate the optical bandgap of pristine and irradiated ZnO and Co-doped ZnO nanoparticles. Enhancement in the PL intensity has been observed in the irradiated samples with respect to their pristine counterparts which can be explained on the basis of the increase of different defect states and Zn-O bonds on the surfaces of the irradiated nanoparticles arising from surface modification. Grain boundaries have played an important role in the optical properties (absorption and PL). © The Royal Society of Chemistry 2014.
Liquid crystal based sensor system for the real time detection of mercuric ions in water using amphiphilic dithiocarbamate
(Elsevier B.V., 2016) Sachin Kumar Singh; Rajib Nandi; Kirtika Mishra; Hemant Kumar Singh; Ranjan Kumar Singh; Bachcha Singh
We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg2+) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methyl-N-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-4′-pentyl biphenyl (5CB) LC, which align LC molecules at aqueous interface and polar head group of the amphiphile acts as mecuric ion specific chelating ligand. When this sensor system was incubated in the aqueous solution containing Hg2+ ions, a dark to bright transition of the image of LCs was observed. This was caused due to rapid and stable complex formation between dithiocarbamate chelating group of MeDTC with Hg2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg2+ ion is 0.5 μM. This sensor did not respond to other metal ions like Pb2+, Cd2+, Cu2+, Zn2+, Na+, Mg2+ and Ca2+, which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg2+ ions in real water samples (tap water). The very simple and effective procedure reported here should facilitate the development of real time, portable and reliable LC based sensor for mercury pollution control. © 2015 Elsevier B.V. All rights reserved.
Modulation of hepatocarcinogenesis in N-methyl-N-nitrosourea treated Balb/c mice by mushroom extracts
(Royal Society of Chemistry, 2016) Srishti Ramsaha; Vidushi S. Neergheen-Bhujun; Shalini Verma; Ashok Kumar; Rahul Kumar Bharty; Amit Kumar Chaudhary; Poornima Sharma; Ranjan Kumar Singh; Priya Huzar Futty Beejan; Kang Kyung-Sun; Theeshan Bahorun
The hepatoprotective potential of edible mushrooms from Mauritius, namely Pleurotus sajor-caju and Agaricus bisporus was evaluated using an N-methyl-N-nitrosourea (MNU)-induced hepatocarcinogenesis Balb/c mice model. Mushroom extracts restored normal weight in MNU treated mice over a 3 month supplementation period. Blood parameter analyses indicated a clear modulation of hemoglobin concentration, leukocyte, platelet, lymphocyte, neutrophil, monocyte and eosinophil counts in MNU-induced mice (p < 0.05). Mushroom extract supplementation effectively reduced oxidative damage in MNU-primed mice, which was marked by a significant decrease in the extent of lipid peroxidation (p < 0.05) and a concomitant increase in the enzymatic antioxidant levels, primarily catalase, superoxide dismutase, glutathione reductase and peroxidase, and FRAP values (p < 0.05). DNA protective effects of the extracts were confirmed by Raman spectroscopy, where, the MNU-DNA interaction, as evidenced by an intense peak at 1254 cm-1, was normalized. The findings demonstrate hepatoprotective, immunomodulatory and anti-carcinogenic effects and suggest the use of mushrooms as potential dietary prophylactics in cancer chemoprevention. © The Royal Society of Chemistry 2016.
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.
Precise analysis of small wavenumber shift of pyridine on dilution with H2O and D2O using RDS technique
(Walter de Gruyter GmbH, 2011) Shivangi Mishra; Tobias Meyer; Jürgen Popp; Ranjan Kumar Singh
The wavenumber difference (Δv) of the ring breathing mode (v 1), ring deformation mode (v12) and C-H stretching mode (v3) of pyridine (Py) dissolved in both H2Oand D 2O at equal mole fractions of the solute (Py) and the solvent (H 2O/D2O) has been determined precisely by using the technique of Raman difference spectroscopy (RDS) in order to analyze the relative shift caused by these two solvents. The spectra of the two systems, for which the difference spectrum is to be generated, were recorded simultaneously and the wavenumber shifts up to almost one hundredth part of the linewidth of a band could be determined precisely. The values of Δv for the three modes as a function of mole fraction are compared with the Δv obtained by the solvation of Py molecule in the media of dielectric constants equal to that of the mixture of Py and H2O/D2O at the experimental mole fractions using DFT and MP2 methods. The variation in Δv with mole fraction seems to be the result of difference of dielectric constants of Py + H2Oand Py + D2Oat equal mole fraction. The absolute peak position and linewidth of the three modes as a function of mole fraction have been discussed in terms of relevant models, which show the effective role of diffusion and concentration fluctuation in the mixture. © by Oldenbourg Wissenschaftsverlag, München.
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.
Role of surface hydrophilicity on MR relaxivity of PEG coated- gadolinium oxide nanoparticles
(Institute of Physics, 2023) Pranjali Pranjali; Deepak Kumar Tripathi; Anamika Chaturvedi; Ranjan Kumar Singh; Krishna Mohan Poluri; Dinesh Kumar; Anupam Guleria
The magnetic resonance (MR) contrast enhancement capabilities of gadolinium oxide nanoparticles (GONPs) have high dependency on its surface chemistry- as the solution properties such as colloidal stability and hydrodynamic diameter of nanoparticles which are prime regulatory parameter for MR relaxivity, are all governed by grafting density of surface material. However, the purification of synthesized surface coated nanoparticles, without compromising the surface properties, remains a major challenge. Among the various cleaning methods, dialysis is often used to remove the unwanted by-products produced during synthesis. However, the effect of dialysis time may significantly impact the surface properties and hence, the MR contrast properties of such nano-formulations. The aim of the present study is to evaluate the effect of dialysis time on surface chemistry and MR contrast enhancement properties of GONPs by comparing the proton relaxivity data. Ultra-small polyethylene glycol (PEG)-coated GONPs with an average particle diameter of 17 nm were synthesized using polyol method. The impact of dialysis time has been investigated systematically on the size distribution, hydrophilicity, magnetic properties, polymer grafting density and relaxometric properties of the as synthesized GONPs. A significant impact of dialysis time was observed on surface chemistry and hence, on the MR relaxivity of synthesized NPs. We evidenced a dramatic decrease in the proton relaxivities of GONPs with increase in dialysis time, which correlated well with the observed decrease in the grafting density of surface polymer. The results clearly indicate that the proton relaxivity of GONPs of similar size and same coating material depends on the surface coating thickness and hydrophilicity of the coating polymer. Overall, it is essential to optimize the accurate time duration of dialysis treatment as the prolonged dialysis may have negative effect on the relaxation times and hence on MR contrast enhancement properties of GONPs. This study is a strategic pathway to fine-tune the dialysis treatment of as-synthesized surface-capped GONPs for pre-eminent MR contrast imaging. © 2022 IOP Publishing Ltd.
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.
Unraveling the physical properties of Mn-doped CdS diluted magnetic semiconductor quantum dots for potential application in quantum spintronics
(Springer, 2022) Piyali Maity; Ravi Kumar; S.N. Jha; D. Bhattacharyya; Ranjan Kumar Singh; Sandip Chatterjee; Anup Kumar Ghosh
The tunability of structural, optical, electronic, and magnetic properties in semiconductor quantum dots (QDs) makes them promising materials for multiple spintronic and optoelectronic applications. However, controlling the size of QDs to tune these properties is challenging due to their quantum size and high sensitivity to the ambient atmosphere. Here, we demonstrate successfully synthesized tunable Mn-doped cadmium sulfide (0% ≤ Mn ≤ 6%) diluted magnetic semiconductor QDs by hot injection chemical route. XRD and TEM studies confirmed that undoped and Mn-doped CdS QDs are polycrystalline in cubic phase without having any dopant-related signature. The XPS study shows the spin–orbit split due to Mn-doping and the atomic percentage of each element present in the prepared sample has been calculated from XPS data. XANES (X-ray Absorption Near Edge Structure) study shows that the Cd has the same oxidation state (+2) in the undoped and Mn-doped CdS QDs and also Mn has +2 oxidation state in Mn-doped CdS QDs. Extended X-ray Absorption Fine Structure (EXAFS) measurements show local structural disorder in higher doping concentration of Mn. It also shows that due to Mn doping, the coordination number of S in all the Mn-doped samples have the S vacancy compared to undoped CdS. No significant change has been observed in FTIR spectra after Mn doping. Raman spectra exhibits two longitudinal optical (LO) modes at 299 cm−1 and 598 cm−1. The intensity of the first LO peak decreases rapidly and linearly due to local structural and short-range disorder induced with increasing Mn concentration in CdS. UV–Vis spectroscopy reveals non-linear variation of bandgap energy showing the downwards bowing with increasing Mn-doping concentration. PL and TRPL indicate appearance of surface defect states with Mn-doping. TRPL spectra show decrease in decay time due to Mn‐doping. Room temperature ferromagnetism of Mn-doped CdS QDs confirms the diluted magnetic semiconductor behavior, which would play key role in quantum spintronics. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.