Borophene Quantum Dots as Novel Peroxidase-Mimicking Nanozyme: A Dual-Mode Assay for the Detection of Oxytetracycline and Tetracycline Antibiotics

Abstract

The greater advantages and wide applications of zero-dimensional nanodots inspire researchers to develop new materials. Therefore, novel borophene quantum dots (QDs) were prepared by a hydrothermal liquid exfoliation technique using water medium. The borophene QDs proved to be highly stable in water medium for more than 120 days. The synthesized borophene QDs revealed intrinsic peroxidase mimetic activity using two chromogenic substrates, 3,3′,5,5′-tetramethylbenzidine (TMB) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS). The excellent intrinsic peroxidase activity toward TMB and ABTS substrates was executed using optimal reaction conditions (pH, borophene QDs' concentration, incubation time, and temperature). The formation of hydroxyl radicals in the presence of H 2 O 2 upon TMB and ABTS oxidation played a significant role in the peroxidase reaction. The borophene QDs further proved to be successful for the colorimetric detection of antibiotics (oxytetracycline and tetracycline) using both TMB and ABTS peroxidase substrates. The limit of detection (LOD) for oxytetracycline and tetracycline was found to be 1.10 and 1.02 μM using TMB and 1.03 and 1.02 μM using ABTS chromogenic substrates, respectively. In addition, the fluorescence sensing of oxytetracycline and tetracycline over borophene QDs was also examined. The high fluorescence of borophene QDs (turn ON) was quenched (turn OFF) by oxytetracycline and tetracycline through the inner filter effect mechanism. The LOD of the fluorescence sensing of oxytetracycline and tetracycline was 1.14 and 1.08 μM, respectively. Interestingly, the borophene QDs could be used for the sensitive and selective colorimetric and fluorometric sensing of oxytetracycline and tetracycline after 120 days of storage. The synthesized borophene QDs with long-term stability and real sample analysis provide new insight as nanozymes with higher peroxidase mimetic and fluorescence performance and can be further exploited for medical diagnosis and environmental toxicants' detection.

Functionalized Borophene Quantum Dots for Fluorescence Sensing of Folic Acid

“…According to the particle size distribution curve (inset of Figure c), B-Arg quantum dots range from 1 to 5.5 nm. The HRTEM (Figure d) reveals a d -spacing of about 0.27 nm, verifying the formation of borophene quantum dots …”

“…Moreover, the presence of the other peaks at 307 cm –1 , 455 cm –1 , 489 cm –1 , and 784 cm –1 is likely linked to the vibrational modes of the χ 3 phase within B-Arg quantum dots. Specifically, these peaks correspond to the A u (Y), B g 1 (Y), A g 4 , and B g 3 vibration modes, respectively. , Raman analysis of B-Arg quantum dots indicates the presence of the β-boron phase alongside the χ 3 phase, resulting from quantum confinement effects …”

“…Major planes such as (003), (110), (104), and (113) appear in both cases and can be indexed to β-rhombohedral boron. ,, However, after the functionalization by Arg molecules (Figure b), the characteristic peaks of borophene nanosheets disappear and are replaced by broad peaks around 20° to 30°. The broadening of the characteristic peaks indicated the formation of small structures, i.e., B-Arg quantum dots, during the functionalization process. , The crystal structure of these quantum dots can be assigned to rhombohedral boron …”

Borophene Quantum Dots with Strong Photoluminescence for Selective Metal Ion Sensing

“…BQDs exhibit versatile optoelectrical characteristics, offering a range of applications. These applications include bioimaging , and photothermal therapy for cancer cells, enhanced photoelectrochemical water splitting activity, improved performance of solar cells, utilization as an active layer in memory devices, molecular sensing of lactate, and detection of various biomarkers , and antibiotics . It is worth noting that until now, the highly fluorescent behavior of BQDs has not been well studied and exploited in various sensing applications.…”