Since the last two decades, protein conjugated fluorescent gold nanoclusters (NCs) owe much attention in the field of medical and nanobiotechnology due to their excellent photo stability characteristics. In this paper, we reported stable, nontoxic and red fluorescent emission BSA-Au NCs for selective detection of L-dopamine (DA) in cerebrospinal fluid (CSF). The evolution was probed by various instrumental techniques such as UV-vis spectroscopy, High resolution transmission electron microscopy (HTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL). The synthesised BSA-Au NCs were showing 4–6 nm with high fluorescent ~8% Quantum yield (QY). The fluorescence intensity of BSA-Au NCs was quenched upon the addition of various concentrations of DA via an electron transfer mechanism. The decrease in BSA-Au NCs fluorescence intensity made it possible to determine DA in PBS buffer and the spiked DA in CSF in the linear range from 0 to 10 nM with the limit of detection (LOD) 0.622 and 0.830 nM respectively. Best of our knowledge, as-prepared BSA-Au NCs will gain possible strategy and good platform for biosensor, drug discovery, and rapid disease diagnosis such as Parkinson’s and Alzheimer diseases.

Because of their large surface area and conductivity, some inorganic materials have emerged as good candidates for the trace-level detection of pharmaceutical drugs. In the present work, we demonstrate the detection of an anticancer drug (regorafenib, REG) by using an electrochemical sensor based on a nanocomposite material. We synthesized a zirconia-nanoparticle-decorated reduced graphene oxide composite (ZrO₂/rGO) using a one-pot hydrothermal method. Reduction of the graphene oxide supports of the Zr²⁺ ions with hydrazine hydrate helped in preventing the agglomeration of the zirconia nanoparticles and in obtaining an excellent electrocatalytic response of the nanostructure ZrO₂/rGO-based electrochemical sensor. Structural and morphological characterization of the nanostructure ZrO₂/rGO was performed using various analytical methods. A novel regorafenib (REG) electrochemical sensor was fabricated by immobilizing the as-prepared nanostructure ZrO₂/rGO on to a glassy carbon electrode (GCE). The resulting ZrO₂/rGO/GCE could be used for the rapid and selective determination of REG in the presence of ascorbic acid and uric acid. The ZrO₂/rGO/GCE showed a linear response for the REG analysis in the dynamic range 11–343 nM, with a remarkable lower detection limit and limit of quantifications of 17 and 59 nM, respectively. The newly developed sensor was used for the accurate determination of REG in both serum samples and pharmaceutical formulations, with satisfactory results.

Little progress has been achieved relating to the preparation of shape-specific carbon quantum dots (CQDs) with a well-ordered edge structure and multi-color fluorescence from a single precursor by monitoring and controlling the reaction time. Selecting phloroglucinol (having suitable three-fold symmetry, C_3h; symmetry elements: E, C₃, C₃ ², σ_h, S₃, S₃ ⁻¹) as a precursor of CQDs is useful for monitoring the shape and structure of CQDs during dehydration mediated controlled growth, which assists to better focus on their formation and PL emission mechanism. We report the rapid synthesis of novel shape-specific (trilateral and quadrilateral) CQDs with multi-color fluorescence emission [blue (B-CQDs), green (G-CQDs), and yellow (Y-CQDs)] by controlling the reaction time. The mechanism of controlled bottom-up growth involves six-membered ring cyclization of the single precursor (phloroglucinol) through the elimination of neighboring active –OH and –H groups in a sulfuric acid medium. Interestingly, wide-range multi-color fluorescence emission of non-nitrogenous CQDs is achieved based on solvatochromism. We consider that the evolution of the tunable photoluminescence (PL) emission can be attributed to both the size of the conjugated domain and oxygen-/sulfur-containing edge electronic states. Furthermore, the multi-color fluorescence CQDs are successfully used as propitious fluorescent probes for multi-color cell (HeLa) and zebra fish larvae imaging owing to an effective intracellular distribution and good biocompatibility.