Para-aminohippuric acid (PAH) serves as a pivotal marker widely employed for accurately estimating effective renal plasma flow, playing a crucial role in the diagnosis and determination of various PAH-related diseases. Consequently, it arises a necessity to devise an advanced quantitative spectrofluorometric technique utilizing fluorescence detection methods for the precise detection of PAH. Therefore, the present work achieved the detection of PAH through a meticulously designed On-Off-On fluorescent nano-system, incorporating graphene quantum dots (CE-GQDs) into cobalt–hemin metal–organic frameworks (Co–hemin MOF). Briefly, the one-pot green synthesis of CE-GQDs was accomplished using the natural precursor derived from the Colocasia Esculenta stem through the hydrothermal method. Subsequently, the synthesized CE-GQD was encapsulated within the Co–hemin MOF, composed of cobalt nitrate hexahydrate as the metal and hemin as a linker. The outcome revealed a wide linear range (20–400 ng/mL) and the lowest detection limit (2.75 ng/mL). CE-GQD exhibited remarkable photoluminescence quenching kinetics towards the metal–organic framework and demonstrated recovery post-sensing. The amino group of PAH readily donates an electron pair to metal ions, facilitating the formation of a coordination bond between PAH and cobalt ions. Consequently, the interaction between carboxyl-enriched CE-GQDs within the designed Co–hemin MOF weakens upon the introduction of PAH. This weakening effect results in the recovery of the quenched fluorescence of CE-GQDs, termed fluorescence “Turn-On”. In conclusion, the preference for CE-GQDs@Co–hemin MOF underscores its high sensitivity and stability for the detection of PAH. Looking ahead, the utilization of CE-GQDs@Co–hemin MOF holds promise for ushering in a new era in PAH sensing.

Quercetin can help with a variety of health problems. Most methods for measuring quercetin in biological fluids are characterized by low sensitivity and selectivity. The employment of metal–organic frameworks in sensor applications with carbon-based materials ushers in a new era. In this study, blue fluorescent graphene quantum dots (GQDs) embedded in a UiO-66-NH₂ metal–organic framework-based nanoprobe (GQDs@UiO-66-NH₂) were constructed for quercetin sensing. Initially, maize husk was used to produce blue fluorescent GQDs, whereas zirconium tetrachloride and 2-aminoterephthalic acid were used to synthesize extremely luminous UiO-66-NH₂. The addition of quercetin to GQDs@UiO-66-NH₂ leads to fluorescence dampening due to the adsorption potential of UiO-66-NH₂. The complexation of zirconium ions with the 3-OH and 4-C＝O functionalities of quercetin resulted in fluorescence quenching. The sensor has a linear concentration range and limit of detection for quercetin of 50–500 and 2.82 ng/mL, respectively. The nanoprobe’s usefulness for quercetin detection was then validated by a selectivity investigation in the presence of interfering chemicals. Furthermore, the percentage relative standard deviations were 4.20% and 2.90%, respectively, indicating great stability and repeatability. Fluorescence “Turn-On–Off” nanoprobes provide a simple, quick, sensitive, and selective method for monitoring quercetin.

The present work aims to synthesize nitrogen-doped reduced graphene oxide-titanium dioxide nanocomposite (N-rGO@TiO₂) using a simple, eco-friendly method and its applications in spectroscopic detection of heavy metal ions such as lead (Pb²⁺), mercury (Hg²⁺), and chromium-VI [Cr(VI)] in potable water. Initially, TiO₂ nanoparticles loaded N doped rGO sheets were fabricated by an ecological method using Gossypium hirsutum (cotton) seeds extract as a green reducing agent. Then, the N-rGO@TiO₂ nanocomposites were subjected for characterizations such as spectroscopic techniques, particle size analysis, zeta potential analysis, and spectroscopic sensing. Notably, the results of this study confirmed that N-rGO@TiO₂ exhibited countless stupendous features in terms of sensing of an analyte. Briefly, the UV-visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy confirmed the successful synthesis of N-rGO@TiO₂. The SEM images showed the wrinkled, folded, and cross-linked network structures that confirmed the surface modification and nitrogen doping in the rGO sheet and synthesis of N-rGO@TiO₂. The EDAX study confirmed the elemental composition of the N-rGO@TiO₂ nanocomposite. Finally, due to the larger surface area, porous nature, high electron mobility, etc. the N-rGO@TiO₂ probe provides the lower detection limit for Pb²⁺, Hg²⁺, and Cr (VI) as low as 50 nM, 15 μM, and 25 nM, respectively. Concisely, our study affirms the admirable sensitivity of N-rGO@TiO₂ nanocomposite to the Pb²⁺, Hg²⁺, and Cr (VI) in potable water can provide better environmental remediation.

Eco-friendly synthesis of nanoparticles is an upcoming discipline of nanoscience. Green synthesis of Ag NPs has gained immense importance and much awareness in developed nations. Fascinatingly, such an environmental friendly synthesis of Ag NPs gives a green chemistry-based non-toxic and economical route to nanotechnology. This review article gives insight into the bioinspired synthesis of Ag NPs and mechanisms involved in the synthesis of Ag NPs. In this review, we have summarized the scientific reports in the eco-friendly synthesis arena of Ag NPs and their applications in the biomedical field. Especially, we have focused on plant materials, fungi, algae, and bacterial potential towards the eco-friendly synthesis of Ag NPs. For future perception, there is a need for in silico and in vitro, in vivo research to authenticate the outcomes.