Construction of N-CDs and Calcein-Based Ratiometric Fluorescent Sensor for Rapid Detection of Arginine and Acetaminophen

Blue light emitting graphene quantum dots/ Rhodamine B doped gold nanostars for ratiometric detection of methotrexate

In this work, an innovative ratiometric sensing platform was developed for the determination of methotrexate (MTX), an antifolate drug, a chemotherapy agent, and an immune system suppressant based on blue emission graphene quantum dots/Rhodamine B doped gold nanostars (B-GQDs/Au NSt-RB). The developed sensor was a dual-emission fluorescent probe with two major emission peaks at 440 nm (B-GQDs) and 580 nm (Au NSt-RB) by exciting at 330 nm. Based on the inhibiting effect of MTX on the system's fluorescence density, the stable ratiometric fluorescent probe was used for the rapid determination of MTX in aquatic solutions and spiked human serum samples. The results indicated good linear correlations over the logarithmic concentration range of 0.3 nM-50.0 μM. In addition, B-GQDs/Au NSt-RB can further realize highly sensitive detection of MTX with a low LOD value of 2.28 × 10-10 M. The RSD% values obtained for the intra-day and inter-day precision were 0.63-3.86 %. With recoveries of 98.2-100.1 % and 98.7-100.5 %, respectively. The short-term temperature and freeze-thaw tests confirmed the higher stability of the developed sensor. In addition, the calculated recoveries for MTX recognition in real samples were in the range of 98-102 %. These findings suggested the excellent potential of the ratiometric fluorescence B-GQDs/Au NSt-RB sensor for detecting MTX in real plasma samples.

A Facile Glycerol-Assisted Synthesis of Low-Cu2+-Doped CoFe2O4 for Electrochemical Sensing of Acetaminophen

This work devised a simple glycerol-assisted synthesis of a low-Cu2+-doped CoFe2O4 and the electrochemical detection of acetaminophen (AC). During the synthesis, several polyalcohols were tested, indicating the efficiency of glycerin as a cosolvent, aiding in the creation of electrode-modifier nanomaterials. A duration of standing time (eight hours) before calcination produces a decrease in the secondary phase of hematite. The synthesized material was used as an electrode material in the detection of AC. In acidic conditions (pH 2.5), the limit of detection (LOD) was 99.4 nM, while the limit of quantification (LOQ) was found to be (331 nM). The relative standard deviation (RSD), 3.31%, was computed. The enhanced electrocatalytic activity of a low-Cu2+-doped CoFe2O4-modified electrode Cu0.13Co0.87Fe2O4/GCE corresponds extremely well with its resistance Rct, which was determined using the electrochemical impedance spectroscopy (EIS) technique and defined its electron transfer capacity. The possibility of a low-Cu2+-doped CoFe2O4 for the electrochemical sensing of AC in human urine samples was studied. The recovery rates ranging from 96.5 to 101.0% were obtained. These findings suggested that the Cu0.13Co0.87Fe2O4/GCE sensor has outstanding practicability and could be utilized to detect AC content in real complex biological samples.

Novel N-doped carbon dots derived from citric acid and urea: fluorescent sensing for determination of metronidazole and cytotoxicity studies

Blue emitting nitrogen-doped carbon dots were synthesized using citric acid and urea through the hydrothermal method, and the fluorescence quantum yield was 35.08%. We discovered that N-CDs featured excellent robust fluorescence stability and chemical resistance. For metronidazole detection, our N-CDs exhibited quick response time, high selectivity and sensitivity, and low cytotoxicity. Specifically, our N-CDs could detect metronidazole in the linear range of 0-179 μM, and the LOD was 0.25 μM. Furthermore, metronidazole efficaciously quenches the fluorescence of N-CDs, possibly owing to the inner filter effect. Lastly, we have employed our N-CDs to detect metronidazole in commercial metronidazole tablets with high accuracy. Overall, the newly prepared fluorescence sensor, N-CDs, demonstrated a huge potential to detect metronidazole in a simple, efficient, sensitive, and rapid manner.