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Item Enhanced photocatalytic removal of Cd(II) from aqueous solution using Bi/S co-doped carbon quantum dots(Elsevier, 2024) Pandey, JayIn this study, S and Bi Co-doped carbon quantum dots were synthesized and their application for Cd(II) removal was investigated. All the experiments were performed in batch mode and effect Bi/S ratio on pH was investigated. It was observed that 12 pH is most suitable for fast removal of Cd2+. The optimized Bi/S ratio was further investigated for effect of adsorbent dosage, initial concentration of Cd(II). Addition of four scavenger solvent namely formaldehyde, acetic acid, ethanediamine and methanol was investigated for enhancement in the photocatalytic activity. Maximum removal efficiency was observed with ethandiamine ∼94% at 300 ppm as compared to formaldehyde (∼90.3%), methanol (∼86.7%) and acetic acid(∼86.3%) indicating that amine group is more suitable as scavenger molecule. Adsorption isotherms of Cd(II) on Bi/S doped on CQD were fitted for different adsorption isotherm model namely Langmuir, Freundlich and Temkin isotherms. Both Lanmguir and Temkin isotherm were observed to fit well with R2 value above 98% as compared to Freundlich with lower R2 value (∼95.3%), indicating that a combination of chemisorption phenomenon as well as availability of energy of electron could be responsible for the Cd(II) removal. Thermodynamic parameters both enthalpy change and entropy change were estimated as −10.76 kJ/mol and −11.2 kJ/mol K. All three parameters were negative indicating that the process was spontaneous and exothermic.Item A carbon quantum dot and rhodamine-based ratiometric fluorescent complex for the recognition of histidine in aqueous systems(RSC, 2019-01) Sidhu, Jagpreet SinghHistidine is an essential α-amino acid that plays a crucial role in tissue development and helps in the transmission of metallic ions during biological events. However, an abnormal level of histidine in the body is associated with various physiological conditions such as arthritis, liver cirrhosis, kidney diseases, and asthma. Herein, a unique ratiometric fluorescence sensing system has been developed for the recognition of histidine. The sensing system was developed using carbon quantum dots (CQDs) as an energy donor and a rhodamine 6G derivative (HS30) as an energy acceptor unit. Interestingly, upon the addition of Fe(III) into the mixture of CQDs and HS30, the phenomenon of fluorescence resonance energy transfer (FRET) was observed when excited at 350 nm. The emergence of a strong emission peak at 551 nm on the addition of Fe(III) suggested the formation of a ratiometric fluorescent complex “CQDs–Fe–HS30”. The ratiometric behavior of “CQDs–Fe–HS30” was studied by monitoring fluorescence emissions at 425 nm and 551 nm with an excitation wavelength of 350 nm. Furthermore, “CQDs–Fe–HS30” was employed for the recognition of histidine in an aqueous system. Due to the high affinity of histidine to Fe(III), the addition of histidine to an aqueous solution of “CQDs–Fe–HS30” resulted in the displacement of the Fe(III) cation from the complex, and the simultaneous quenching and enhancement of the emission peaks at 551 nm and 425 nm, respectively, was observed. The developed sensing system was successfully employed for a histidine recovery experiment in human urine samples with satisfactory results. Furthermore, the mixture of CQDs and HS30 was successfully utilized to implement an inhibit logic gate with Fe(III) and histidine as inputs and emission at 551 nm as output.Item The Photochemical Degradation of Bacterial Cell Wall Using Penicillin-Based Carbon Dots: Weapons Against Multi-Drug Resistant (MDR) Strains(Wiley, 2017-10) Sidhu, Jagpreet SinghInability of antibiotics repertoire to effectively control the progress of multi-drug resistant (MDR) bacteria has prompted the substantial curiosity among the scientists to seek new tactics to combat the bacterial growth. Therefore, to eradicate the pathogenic bacteria with least cytotoxicity, we employed carbon dots as a broad spectrum of antibacterial weapons in the presence of visible light. Instead of using citric acid, we engaged the penicillin G as a carbon source for the synthesis of penicillin carbon dots (PCDs), which made the carbon dots more aggressive towards pathogenic microbes. Penicillin was also covalently attached to –NH2 containing citric acid based CDs (CDs-Penicillin) via an amide bond to evaluate whether penicillin in the form of PCD has retained its activity or in its conjugated form (CDs-Penicillin). Synthesized dots were assessed for their antibacterial activity against Staphylococcus aureus, Escherichia coli (DH5α), MDR Escherichia coli and Methicillin-resistant Staphylococcus aureus in the presence as well as the absence of visible light. The mechanism of bacteria-killing through cell wall rupturing was investigated using scanning electron microscopy. Antibacterial assay demonstrates that penicillin in the form of PCDs retained its activity and possess great prospects in the development of new bactericidal therapies to invade the MDR bacteria. Cytotoxicity of both PCDs and CDs-Penicillin has been evaluated by measuring the viability of human HeLa cells. Fluorescence images of bacteria collected using different excitation wavelength.Item Biocompatible carbon dots derived from κ-carrageenan and phenyl boronic acid for dual modality sensing platform of sugar and its anti-diabetic drug release behavior(Elsevier, 2019-07) Gangopadhyay, SubhashisDetection of sugar by enzymatic assay has been suffering from costly, time-taking, instable and denaturation of glucose oxidase. Recently, chemosensors that have affinity towards boronate became the hot topic in the domain of monosaccharide detection. In this work, a novel strategy was addressed to fabricate carbon dots (C-dots) from linear sulfated polysaccharides κ- carrageenan and phenyl boronic acid for nonenzymatic monosaccharide (glucose) detection. The boronic acid group anchored C-dots surface can form assembly by covalently bonded with the cis-diol moiety of the glucose which caused fluorescence quenching of the C-dots. The inert surface nature of the luminescent C-dots enables them to sense as low as 1.7 μM glucose without the interference of other biomolecules. The proposed sensing system was successfully applied for assay of glucose in blood serum. Interestingly, these C-dots were used as a nano vehicle for delivery of anti-diabetic drug Metformin. Good biocompatibility results were found with MTT and hemolysis assay. Owing to its simplicity and effectiveness, the as-prepared C-dots offered great promise for blood sugar diagnosis and treatment.Item Zinc and nitrogen ornamented bluish white luminescent carbon dots for engrossing bacteriostatic activity and Fenton based bio-sensor(Elsevier, 2018-07) Gangopadhyay, SubhashisCarbon dots with heteroatom co-doping associated with consummate luminescence features are of acute interest in diverse applications such as biomolecule markers, chemical sensing, photovoltaic, and trace element detection. Herein, we demonstrate a straightforward, highly efficient hydrothermal dehydration technique to synthesize zinc and nitrogen co-doped multifunctional carbon dots (N, Zn-CDs) with superior quantum yield (50.8%). The luminescence property of the carbon dots can be tuned by regulating precursor ratio and surface oxidation states in the carbon dots. A unique attribution of the as-prepared carbon dots is the high monodispersity and robust excitation-independent emission behavior that is stable in enormously reactive environment and over a wide range of pH. These N, Zn-CDs unveils captivating bacteriostatic activity against gram-negative bacteria Escherichia coli. Furthermore, the excellent luminescence properties of these carbon dots were applied as a platform of sensitive biosensor for the detection of hydrogen peroxide. Under optimized conditions, these N, Zn-CDs reveals high sensitivity over a broad range of concentrations with an ultra-low limit of detection (LOD) indicating their pronounced prospective as a fluorescent probe for chemical sensing. Overall, the experimental outcomes propose that these zero-dimensional nano-dots could be developed as bacteriostatic agents to control and prevent the persistence and spreading of bacterial infections and as a fluorescent probe for hydrogen peroxide detection.Item Heteroatom doped blue luminescent carbon dots as a nano-probe for targeted cell labeling and anticancer drug delivery vehicle(Elsevier, 2019-11) Gangopadhyay, SubhashisHerein, a simple and efficient method to fabricate nitrogen and sulphur doped photoluminescent carbon dots (C-dots) has been judiciously developed for targeting cancer cells. Advancement in newfangled imaging tool for cancer cells is a vital and highly trustworthy strategy for cancer therapy. The fluorescent C-dots prepared from κ-carrageenan and folic acid can serve as an efficient cargo for cancer cell labeling expressing the folate receptor on their surface. The prepared C-dots unveiled good water solubility, excellent photostability, and biocompatibility. The C-dots played the role of nano-vehicle for anticancer drug capecitabine under different pH environments. Also, C-dots were applied as invisible marker and finger print recovery applications. The folate receptor in C-dots led to amazing targetability of cancer cells and which embraces a great promise in biomedical studies.Item Stability of carbon quantum dots: a critical review(RSC, 2023) Bhatt, GeetaCarbon quantum dots (CQDs) are fluorescent carbon nanomaterials with unique optical and structural properties that have drawn extensive attention from researchers in the past few decades. Environmental friendliness, biocompatibility and cost effectiveness of CQDs have made them very renowned in countless applications including solar cells, white light-emitting diodes, bio-imaging, chemical sensing, drug delivery, environmental monitoring, electrocatalysis, photocatalysis and other related areas. This review is explicitly dedicated to the stability of CQDs under different ambient conditions. Stability of CQDs is very important for every possible application and no review has been put forth to date that emphasises it, to the best of our knowledge. This review's primary goal is to make the readers cognizant of the importance of stability, ways to assess it, factors that affect it and proposed ways to enhance the stability for making CQDs suitable for commercial applications.