Search

Label-free and sensitive detection of PSA (Prostate Specific Antigen) is still a big challenge in the arena of prostate cancer diagnosis in males. We present a comparative study for label-free PSA aptasensor and PSA immunosensor for the PSA-specific monoclonal antibody, based on graphene quantum dots-gold nanorods (GQDs-AuNRs) modified screen-printed electrodes. GQDs-AuNRs composite has been synthesized and used as an electro-active material, which shows fast electron transfer and catalytic property. Aptamer or anti-PSA has immobilized onto the surface of modified screen printed electrodes. Three techniques are used simultaneously, viz. cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedence spectroscopy (EIS) to investigate the analytical performance of both PSA aptasensor and PSA immunosensor with its corresponding PSA antigen. Under optimum conditions, both sensors show comparable results with an almost same limit of detection (LOD) of 0.14 ng mL -1 . The results developed with aptasensor and anti-PSA is also checked through the detection of PSA in real samples with acceptable results. Our study suggests some advantages of aptasensor in terms of better stability, simplicity and cost effectiveness. Further our present work shows enormous potential of our developed sensors for real application using voltammetric and EIS techniques simultaneous to get reliable detection of the disease.

[Display omitted] • Facile hydrothermal synthesis of high-quality phosphorus-doped TMD quantum dots, graphene-like structure. • P-MoS 2 QDs show remarkable sensing features for the detection of HbA1c. • The sensor response was linear from 2-15%, within the typical physiological range (0.75-22.93 mM). Highly fluorescent transition metal dichalcogenides (TMDs) based quantum dots (QDs) have been the focus of immense research owing to their bio-compatibility, non-toxicity, easy chemical synthesis and broad spectrum of applications which includes biosensing, optoelectronics, energy storage devices, etc. Herein, we present a one-step hydrothermal growth of in-situ blue fluorescent phosphorous doped-molybdenum di sulfide QDs (P-MoS 2 QDs) in aqueous media. A range of functional groups over the surface of chemically synthesized P-MoS 2 QDs helps in conserving its fluorescence along with high aqueous stability and solubility. Besides, remarkable photoluminescence (PL) properties of P-MoS 2 QDs were then explored to concoct an optical sensor with excellent selectivity and sensitivity for glycated hemoglobin (HbA1c) followed by functionalization with boronic acid. The response of the sensor was found to be linear in the range of 2–15 %, which is under the typical physiological aliquot range (0.75–22.93 mM with limit of detection to be 77.5 μM, under optimized conditions. Moreover, PL quenching processes and TRPL data of P-MoS 2 QDs were explored to elucidate the plausible quenching mechanism which suggests mixed kind of quenching processes. In conclusion, we envisaged that the present methodology can provide an effective and potent tool for HbA1c sensing in real biological (hemolysate/whole blood-lysate) samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ one-pot hydrothermal-synthesis of MoTe 2 @C NDs was detailed. • MoTe 2 @C NDs' potency in biosensing was explored. • MoTe 2 @C NDs were characterized by using XPS, Raman spectroscopy, XRD and TEM. • Upon gradual-proliferation of H 2 O 2 , MoTe 2 @C NDs sensed H 2 O 2 significantly (LOD = 14.22 nM). • The PL quenching-mechanism was elucidated based on three-level kinetic model considering charge separated-trap states. Transition metal dichalcogenides (TMDs) based materials have grabbed striking attention to a great extent owing to their intriguing characteristics for biological, optical, chemical and medicinal applications. Herein, we report in-situ one-pot hydrothermal-synthesis of molybdenum ditelluride@carbon nano-dots (MoTe 2 @C NDs) and then explored its potency in biosensing. The MoTe 2 @C NDs have been characterized by using X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy and Transmission Electron Microscopy (TEM) for confirmation. Furthermore, the photophysical properties of MoTe 2 @C NDs have been examined. Under radiation of Ultra-Violet (UV) light (λ = 365 nm), the MoTe 2 @C NDs emit cyan fluorescence which has been confirmed by photoluminescence (PL) spectroscopy (PL peak at ∼431 nm, excitation wavelength ∼350 nm). The as-synthesized sample has been subjugated for the sensing of hydrogen-peroxide (H 2 O 2) molecules. Notably, with a gradual proliferation of the concentration of H 2 O 2 , the PL intensity of the MoTe 2 @C NDs decreases and is found to be linear (R2 = 0.9986). The detection-limit has also been estimated as 14.22 nM. The PL quenching-mechanism has been elucidated based on three-level kinetic model considering charge separated-trap states (1[D+···A−] ↔ 3[D+···A−]). This is the first work of hydrothermal-synthesis of MoTe 2 @C NDs and study of its optical properties, which has efficient potential to use as H 2 O 2 sensor in industrial/biomedical applications. [ABSTRACT FROM AUTHOR]

Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm2 with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors. • GQDs are derived from the bio-waste Marigold flower via hydrothermal method. • Demonstrates high specific capacitance in aqueous KOH electrolyte. • Exhibits high values of energy (17.78 Wh/kg) and power (799.70 W/kg) densities. • Displays good rate performance & better cyclic stability. • Confirms its sustainable electrocapacitive nature. [ABSTRACT FROM AUTHOR]

A voltammetric method is described for the determination of chloroquine (CQ) and validated simultaneously by two techniques and in three different conditions. The WS2 quantum dots (WS2 QDs) were synthesized by a hydrothermal method and then placed on reduced graphene oxide (rGO) sheets. The resulting composite material was then deposited on a glassy carbon electrode (GCE) where it showed excellent electroactivity. The modified GCE responds to chloroquine at a typical potential maximum of 1.2 V (vs. AgCl/Ag). Techniques including cyclic voltammetry and differential pulse voltammetry were tested. Features of merit include (a) a wide linear response (in the 0.5 μM to 82 μM CQ concentration range), (b) an electrochemical sensitivity of 0.143–0.90 μA·μM−1·cm−2), and a 40–120 nM limit of detection (at S/N = 3). The sensor has excellent selectivity even in the presence of potentially interfering biological compounds. Responses were tested in phosphate buffer, human serum and pharmaceutical formulations, and no cross reactivity or matrix effects were found. In all the three cases, quite satisfactory recoveries were obtained. [ABSTRACT FROM AUTHOR]