Abstract:In this study, highly fluorescent sulfur and nitrogen doped carbon quantum dots (S,N-CQDs) were used as fluorescent nanosensors for direct spectrofluorimetric estimation of each of gliclazide (GLZ) and saxagliptin (SXG) without any pre-derivatization steps for the first time. S,N-CQDs were synthesized employing a simple hydrothermal technique using citric acid and thiosemicarbazide. The produced S,N-CQDs were characterized using different techniques including fluorescence emission spectroscopy, UV spectrophoto… Show more
“…For ONZ, the K SV values were 18.2 × 10 3 , 17.05 × 10 3 , and 16.65 × 10 3 , while for MIZ the K SV values were 4.65 × 10 3 , 3.3 × 10 3 , and 0.95 × 10 3 at 298, 308, 318 K, respectively. As a result, in addition to the previously discussed IFE, the mechanism of quenching for both ONZ and MIZ is the static quenching since K SV decreased by increasing the temperature 58 – 60 . Figure 9 Stern–Volmer plots for the quenching of Ag-NPs fluorescence at three different temperature settings (298, 308, and 318 K) by different concentrations of ( a ) ONZ (20.0, 40.0, 60.0 μM), ( b ) MIZ (20.0, 40.0, 60.0 μM).…”
A green and simple method was proposed for the synthesis of silver nanoparticles (Ag-NPs) using Piper cubeba seed extract as a reducing agent for the first time. The prepared Ag-NPs were characterized using different spectroscopic and microscopic techniques. The obtained Ag-NPs showed an emission band at 320 nm when excited at 280 nm and exhibited strong green fluorescence under UV-light. The produced Ag-NPs were used as fluorescent nanosensors for the spectrofluorimetric determination of ornidazole (ONZ) and miconazole nitrate (MIZ) based on their quantitative quenching of Ag-NPs native fluorescence. The current study introduces the first spectrofluorimetric method for the determination of the studied drugs using Ag-NPs without the need for any pre-derivatization steps. Since the studied drugs don't exhibit native fluorescent properties, the importance of the proposed study is magnified. The proposed method displayed a linear relationship between the fluorescence quenching and the concentrations of the studied drugs over the range of 5.0–80.0 µM and 20.0–100.0 µM with limits of detection (LOD) of 0.35 µM and 1.43 µM for ONZ and MIZ, respectively. The proposed method was applied for the determination of ONZ and MIZ in different dosage forms and human plasma samples with high % recoveries and low % RSD values. The developed method was validated according to ICH guidelines. Moreover, the synthesized Ag-NPs demonstrated significant antimicrobial activities against three different bacterial strains and one candida species. Therefore, the proposed method may hold potential applications in the antimicrobial therapy and related mechanism research.
“…For ONZ, the K SV values were 18.2 × 10 3 , 17.05 × 10 3 , and 16.65 × 10 3 , while for MIZ the K SV values were 4.65 × 10 3 , 3.3 × 10 3 , and 0.95 × 10 3 at 298, 308, 318 K, respectively. As a result, in addition to the previously discussed IFE, the mechanism of quenching for both ONZ and MIZ is the static quenching since K SV decreased by increasing the temperature 58 – 60 . Figure 9 Stern–Volmer plots for the quenching of Ag-NPs fluorescence at three different temperature settings (298, 308, and 318 K) by different concentrations of ( a ) ONZ (20.0, 40.0, 60.0 μM), ( b ) MIZ (20.0, 40.0, 60.0 μM).…”
A green and simple method was proposed for the synthesis of silver nanoparticles (Ag-NPs) using Piper cubeba seed extract as a reducing agent for the first time. The prepared Ag-NPs were characterized using different spectroscopic and microscopic techniques. The obtained Ag-NPs showed an emission band at 320 nm when excited at 280 nm and exhibited strong green fluorescence under UV-light. The produced Ag-NPs were used as fluorescent nanosensors for the spectrofluorimetric determination of ornidazole (ONZ) and miconazole nitrate (MIZ) based on their quantitative quenching of Ag-NPs native fluorescence. The current study introduces the first spectrofluorimetric method for the determination of the studied drugs using Ag-NPs without the need for any pre-derivatization steps. Since the studied drugs don't exhibit native fluorescent properties, the importance of the proposed study is magnified. The proposed method displayed a linear relationship between the fluorescence quenching and the concentrations of the studied drugs over the range of 5.0–80.0 µM and 20.0–100.0 µM with limits of detection (LOD) of 0.35 µM and 1.43 µM for ONZ and MIZ, respectively. The proposed method was applied for the determination of ONZ and MIZ in different dosage forms and human plasma samples with high % recoveries and low % RSD values. The developed method was validated according to ICH guidelines. Moreover, the synthesized Ag-NPs demonstrated significant antimicrobial activities against three different bacterial strains and one candida species. Therefore, the proposed method may hold potential applications in the antimicrobial therapy and related mechanism research.
“…Carbon quantum dots (CQDs) have drawn worldwide attention in the family of carbon nanomaterials because of their superior hydrophilicity, excellent conductivity, biocompatibility, low toxicity, high water solubility, photostability, eco-friendliness, tunability, and fluorescence properties. , CQDs have been used in applications such as sensing, solar cells, supercapacitor, bioimaging, drug delivery, and photocatalysis. − Because of being eco-friendly and affordable, a diversity of biowaste is used to synthesize CQDs. Rice (Oryza sativa), a rich source of carbohydrates, is one of the most significant cultivated harvests in the world .…”
Herein, eco-friendly, water-soluble, and fluorescent carbon quantum dots (CQDs) with an average size of 8.3 nm were synthesized from rice husk (RH) using the hydrothermal method, and the CQDs were labeled as rice husk CQDs (RH-CQDs). The composition and surface functionalities were studied using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. A study on the impact of pH and irradiation time on fluorescence affirmed the stability of RH-CQDs. The assynthesized nanosensor has high selectivity and sensitivity for Fe 3+ ions. Several photophysical studies were performed to investigate the interaction between RH-CQDs and Fe 3+ . Using the time-correlated single-photon technique, it is determined that the average lifetime value of RH-CQDs significantly decreases in the presence of Fe 3+ , which supports a dynamic quenching mechanism. The developed sensor exhibited excellent sensitivity with a detection limit in the nanomolar range (149 nM) with a wide linear range of 0−1300 nM for Fe 3+ ions. The prepared nanosensor was also used to detect Fe 3+ in a tablet supplement with high recoveries. Moreover, the RH-CQD nanoprobe was used to detect other analytes (fluoroquinolones) using the fluorescence enhancement technique. It showed high selectivity and sensitivity toward ofloxacin (OFX) and ciprofloxacin (CPX). The detection limits calculated were 150 nM and 127 nM with a linearity range of 50−1150 nM for OFX and CPX, respectively. The enhancement of the average lifetime value and quantum yield in the presence of OFX and CPX favors the increased fluorescence property of RH-CQDs through hydrogen bonding and charge transfer. In this work, the integration of two different mechanisms (fluorescence quenching and fluorescence enhancement) was followed to construct a single sensing platform for accurate quantification of dual-mode nanosensors for the detection of metal ions and fluoroquinolones by the excited-state electron transfer and hydrogen bonding mechanism, respectively. This strategy also stimulates the detection of more than one analyte.
“…Doping is the insertion of heteroatoms like (boron, sulfur, nitrogen, or phosphorous) into the general structure of CQDs with or without modification in their surface. Doping of CQDs results in increasing the quantum yield and improving the fluorescence properties of CQDs, which in turn increases their applications [16,[37][38][39]. NS@CQDs have been repeatedly studied as carbon and nitrogen have the same atomic radius, in addition, sulfur and carbon are actually close in electronegativity [40].…”
A validated, sensitive, and simple spectrofluorimetric method was developed for the analysis of two important CNS-acting drugs, olanzapine and diazepam, in their commercial tablets without the need for any pretreatment steps. The developed method relied on the quantitative quenching effect of each of olanzapine and diazepam on the native fluorescence of nitrogen and sulfur-doped carbon quantum dots (NS@CQDs). NS@CQDs were prepared from thiosemicarbazide and citric acid by a facile one-pot hydrothermal technique. The synthesized NS@CQDs were characterized by different spectroscopic and microscopic techniques. NS@CQDs produced a maximum emission peak at 430 nm using 360 nm as an excitation wavelength. Calibration curves showed a good linear regression over the range of 5.0–200.0 and 1.0–100.0 μM with detection limits of 0.68 and 0.29 μM for olanzapine and diazepam, respectively. The adopted method was used for the determination of the investigated drugs in their tablets with high % recoveries (98.84–101.70%) and low % RSD values (< 2%). As diazepam is one of the most commonly abused benzodiazepines, the developed method was successfully applied for its determination in spiked human plasma with high % recoveries and low % RSD values, providing further insights for monitoring its potential abuse. The quenching mechanism was also studied and confirmed to be through dynamic and static quenching for olanzapine and diazepam, respectively. Due to the high selectivity and sensitivity, content uniformity testing of low-dose tablets was successfully performed by applying the United States Pharmacopoeia guidelines. The method's validation was performed in compliance with ICHQ2 (R1) recommendations.
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