Orange peel-derived carbon dots/Cu-MOF nanohybrid for fluorescence determination of l-ascorbic acid and Fe3. Anal Chim Acta 2024;1287:342066. [PMID: 38182373 DOI: 10.1016/j.aca.2023.342066]

Ratiometric fluorescence assay for ciprofloxacin in human blood serum and urine samples based on sulfur-doped carbon dots/rhodamine B nanohybrid encapsulated HKUST-1 metal-organic framework

Preparation of carbon dots (CDs) from biomass waste is of great interest due to its low cost synthesis, environmental compatibility and functionalization without adding dangerous chemicals. Herein, S-doped carbon dot (SCD) was synthesized using agricultural waste as carbon precursors and modified in-situ with rhodamine B dye (SCD@RHB) to construct efficient flouresent probe. SCD@RHB was loaded into HKUST-1 metal-organic framework (SCD@RHB/HKUST-1) and the probe was employed as ratiometric flouresent (RF) sensor for the determination of ciprofloxacin (CIP) antibiotic in trace level. The sensor emits two-resolved peaks at 415 and 575 nm under excitation wavelength of 310 nm which are due to the characteristic fluorescence emissions of SCD and RHB, respectively. Under optimal conditions, the emissions of SCD and RHB change oppositely in the presence of CIP which can be used to evaluate the sensing performance of probe. The ratiometric SCD@RHB/HKUST-1 nanohybrid has a wide linear range (0.1-300 μM) with a low detection limit of 21.3 nM along with good sensitivity and selectivity for CIP. The probe was also used for the determination of CIP in human blood and urine samples. The results demonstrated rapid and accurate analysis with reasonable recoveries of 94 to 102 % for blood sample and 94-106 % for urine sample. This strategy provides a conveninet way to design RF sensors based on HKUST-1.

Applications of Functionalized Carbon-Based Quantum Dots in Fluorescence Sensing of Iron(III)

Iron, an essential trace element exhibits detrimental effects on human health when present at higher or lower concentration than the required. Therefore, there is a pressing demand for sensitive and selective detection of Fe3+ in water, food etc. Unfortunately, in several instances, the traditional approaches suffer from a number of shortcomings like complicated procedures, limited sensitivity, poor selectivity and more expensive and time consuming. The scope of optical tuning and excellent photophysical properties of carbon- based nanomaterials like carbon dots (C-dots) and graphene dots (g-dots) have made them promising optical sensors of metal ions. Moreover, high surface area, superior stability of such materials contributes towards the fruitful development of sensors. The present review offered critical information on the fabrication and fluorimetric applications of these functional nanomaterials for sensitive and selective detection of Fe3+. An in-depth discussion on fluorescent C-dots made from naturally occurring materials and chemical techniques were presented. Effect of doping in C-dots was also highlighted in terms of improved fluorescence response and selectivity. In a similar approach g-dots were also discussed. Many of these sensors exhibited great selectivity, superior sensitivity, high quantum yield, robust chemical and photochemical stability and real-time applicability. Further improvement in these factors can be targeted to develop new sensors.

Comparison of Synthetic Pathways for Obtaining Fluorescent Nanomaterials Based on Halloysite and Carbon Dots for Potential Biological Sensing

Recently, fluorescent sensors have gained considerable attention due to their high sensitivity, low cost and noninvasiveness. Among the different materials that can be used for this purpose, carbon dots (CDs) represent valuable candidates for applications in sensing. These, indeed, are easily synthesized, show high quantum yield and are highly biocompatible. However, it was pointed out that the photoluminescence properties of these nanomaterials are strictly dependent on the synthetic and purification methods adopted. The presence of halloysite nanotubes (HNTs), a natural, low cost and biocompatible clay mineral, has been found to be efficient in obtaining small and highly monodispersed CDs without long and tedious purification techniques. Herein, we report the comparison of synthetic pathways for obtaining halloysite-N-doped CDs (HNTs-NCDs) that could be used in biological sensing. One was based on the synthesis of N-doped CDs by a bottom-up approach on HNTs' surface by a MW pyrolysis process; the other one was based on the post-modification of pristine N-doped CDs with halloysite derivatives. The evaluation of the best synthetic route was performed by different physico-chemical techniques. It was found that the bottom-up approach led to the formation of N-doped CDs with different functional groups onto the HNTs' surface. This evidence was also translated in the different fluorescence quantum yields and the existence of several functional groups in the obtained materials was investigated by potentiometric titrations. Furthermore, the ability of the synthesized nanomaterials as sensors for Fe3+ ions detection was assessed by spectroscopic measurements, and the cellular uptake was verified by confocal/fluorescence microscopies as well.