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Herein, we demonstrated the synthesis and properties of zinc titanate (ZnTiO3) nanoparticle prepared through the sol-gel method. The structural and morphological properties were studied using XRD, FTIR, Raman, SEM and EDS techniques; the results confirmed the successful formation of the ZnTiO3 perovskite nanoparticle. The UV–Vis spectrum shows the maximum absorption near the visible region of 390 nm and the optical band gap was found to be 2.13 eV. The photoluminescence studies revealed visible greenish-blue emission under the excitation of 350 nm. This biosensor capability of the proposed material was studied under electrochemical sensing platform to determine the concentration of urea at a low level using the graphite electrode modified with ZnTiO3 nanoparticle. The results evidenced that, the graphite electrode modified with ZnTiO3 nanoparticle is highly sensitive towards urea at a linear range from 30 µM to 150 µM with the limit of detection of 76.16 µM and sensitivity of 19.95 mA µM-1cm−2. Hence, this novel method of perovskite-based electrochemical sensor will be used as a promising stable material in the field of urea related disease diagnosis.

This paper reports on the development of an N-doped zinc oxide nanoparticle (N–ZnO) based optical biosensor for selective urea detection. The N–ZnO nanoparticle has a particle size of 10 nm with a bandgap of 2.6 eV, and it exhibits fluorescence emission at 385 nm under an excitation of 340 nm. The optical sensing of N–ZnO was examined in the presence of various biomolecules such as urea, glucose, thiourea, sucrose and BSA. The fluorescence response through the electron–hole recombination energy transfer process was observed in all the N–ZnO and biomolecule combinations. The optical sensing response was selectively high for urea compared to the other aforementioned compounds. The results confirm higher sensitivity for urea detection in the presence of N–ZnO with a linear range of 2.6–26 μM at a detection limit of 4.93 ± 0.02 μM. Furthermore, the higher sensitivity and recovery of urea in the blood serum validates the efficacy of N–ZnO. The outcome of the reported work suggests that N–ZnO can be used as a promising nanomaterial for a quick-time optical biosensing system for urea detection and also as a pH sensing probe in clinical applications.

Fluorescence labelling is one of the significant properties for optical bioimaging and biosensing applications. The development in the field of nanotechnology has created enormous conveniences in biomedical research. The fluorescence enhancement of mammalian cell in presence of zinc nitride colloidal nanoparticle was imaged using multiphoton confocal microscope. The statistical significance in the presence and absence of nanoparticle evidenced the fluorescence intensity enhancement in the cells. In order to suppress the background signal and increase the penetration depth, the multiphoton technique is utilized by 740 nm excitation to examine the enhancement potential of Zn3N2 colloidal nanoparticles towards cell structures. Hence, we suggest that, the unique feature of inorganic nanomaterial is a promising material for probing cells for future diagnostic applications.

Herein, we propose a facile electrochemical sensing platform for urea detection using pencil graphite electrode modified nanocomposites of CuO/ZnO and Fe

In this work, we have reported on the facile synthesis of white light-emitting carbon quantum dots (CQD) from corncob by hydrothermal method. This CQD has a broad emission from 380 nm to 650 nm with high photoluminescence intensity even after three months of shelf-life and stable at variable pH conditions. The presence of Si and N impurities in the biomass gives a greater advantage in producing white light emission with high quantum yield (54%) and enhanced lifetime at ambient conditions. The CQD is highly sensitive towards DNA, paracetamol, Pb2+, Cu2+, Fe3+, and Cr3+ fluorescence sensing and signifies its application as a multi-modal fluorescence sensor. The results of optical sensitivity calculated from the linear range of 1‐10 ng/mL, 0.10‐0.30 mg/mL, 2.5446 ng/mL, 0.0694 mg/mL, 0.3103–1.5515 μM/mL, 0.4299–4.7293 μM/mL, 1.3010 μM/mL and 0.05–2.5 μM/mL. The limit of detection is 2.5446 ng/mL, 0.0694 mg/mL, 0.8641 μM/mL, 1.2454 μM/mL, 1.3010 μM/m, 0.8550 μM/mL and 2.8562 μM/mL, respectively. And also, the relative standard deviation values of 2.30%, 4.46%, 1.79%, 1.84%, 0.26%, 1.23% and 0.35% are evidences its possibility of development towards potential optical sensor applications. Flexible white light-emitting sheets were fabricated from the CQD, illuminates uniform brightness, and has good color reproducibility and higher stability under various UV light excitation.

Colloidal inorganic nanoparticles have a significant impact for biosensing due to its precise biomolecular interaction. Herein, we report on the efficiency of silica-silver colloidal nanoparticles towards optical biosensor application. Silica colloids was prepared by the sol-gel method using biomass of rice husk as a precursor and then composited with silver colloids. The size of silica and silver (SiO2-Ag) colloidal nanoparticles was found to be 80 nm and 75 nm, respectively. The SiO2-Ag colloidal nanoparticles have the unique fluorescence at 325 nm with an excitation of 260 nm, which is significant for the excitation of most biomolecules, organelle stains and fluorescent labelling. The biosensing properties were validated against biomolecules such as glucose, uric acid, paracetamol, ascorbic acid and dopamine through plasmon resonance energy transfer (PRET) process by fluorescence spectroscopic technique. The glucose molecules responded with good sensing efficacy and the detection limit was found to be 0.49 µM. The proof of efficient glucose sensing of the SiO2-Ag colloidal nanoparticles also validated on human urine and serum and it gives the maximum recovery of 99.3 % and 98.2 %, respectively. These results support the efficacy of SiO2-Ag colloidal nanoparticles for optical biosensing applications in future.