Rice Husk-Derived Carbon Quantum Dots-Based Dual-Mode Nanoprobe for Selective and Sensitive Detection of Fe³⁺ and Fluoroquinolones

Abstract

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.

Dual-Emissive Carbon Dots: Exploring Their Fluorescence Properties for Sensitive Turn-Off–On Recognition of Ferric and Pyrophosphate Ions and Its Application in Fluorometric Detection of the Loop-Mediated Isothermal Amplification Reaction

“…In comparison, the K r (1.09 × 10 8 s –1 ) for CDs in ethanol solvent remained almost similar, while K nr showed a substantial decrease to 3.80 × 10 8 s –1 . All these observations indicate that the observed fluorescence enhancement of CDs in ethanol is primarily caused by the deactivation of the nonradiative recombination pathway. , Moreover, CDs exhibited similar kinds of emission maxima and fluorescence intensity enhancement in all four different alcohol solvents (methanol, ethanol, isopropanol, and butanol) (Figure S6). Though the four alcohol solvents possess varying degrees of solvent polarities, the obtained result suggests that the red emission of CDs is primarily driven by the presence of the −OH group. , Interestingly, the fluorescence properties of CDs showed a reversible response in the presence of water and ethanol; that is, the addition of water to the ethanol solution of CDs quenches the fluorescence intensity and retains the dual-emissive nature of the CDs, while the addition of ethanol to the aqueous dispersion of CDs results in fluorescence enhancement.…”

One-Step Solvothermal Synthesis of Red Chiral Carbon Dots for Multioptical Detection of Water in Organic Solvents

“…20 The two absorption peaks at ∼230 and ∼260 nm are observable in the UV−visible spectra of RC-CDs that are related to the π−π* transitions of the C�C bonds of sp 2 domains in the aromatic structure of the carbon core. 16,21 The RC-CDs exhibited distinct absorption peaks at ∼410, ∼560, and ∼610 nm, indicating that RC-CDs possessed different surface states. 22 In other words, the emergence of absorption peaks in longer wavelengths of the UV−visible spectra can be a hopeful symptom of red fluorescent emissions that is very important for their future biological and medical applications.…”

Yellow emissive nitrogen-doped carbon dots as a fluorescence probe for the sensitive and selective detection of silver ions

“…7 Fluorescence detection is proved to be an effective method for metal ion detection in food and environmental samples owing to the advantages of simple operation, rapid response, low cost and good selectivity. [8][9][10] Recently, carbon dots (CDs) have attracted much consideration due to their outstanding features such as fast synthetic route, easy surface functionalization, environmental friendliness, low cost and good uorescence properties, which can be used as a new type of uorescent materials to replace quantum dots and organic dyes in the eld of sensing. [11][12][13][14] Heteroatomic doping could induce the Fermi level to move up and greatly improve the photoluminescence performance of CDs, thereby expanding the application scope.…”

“…7 Fluorescence detection is proved to be an effective method for metal ion detection in food and environmental samples owing to the advantages of simple operation, rapid response, low cost and good selectivity. 8–10…”