Highly fluorescent composite of boron nitride quantum dots decorated on cellulose nanofibers for detection and removal of Hg(II) ions from waste water.

To address the challenge of heavy-metal ions in wastewater, boron nitride quantum dots (BNQDs) were synthesized in-situ on rice straw derived cellulose nanofibers (CNFs) as substrate. The composite system exhibited strong hydrophilic-hydrophobic interactions, as corroborated by FTIR, integrated the extraordinary fluorescence properties of BNQDs with fibrous-network of CNFs (BNQD@CNFs) yielding a surface of 35.147 m2 g-1 of luminescent fibers. Morphological studies revealed uniform distribution of BNQDs on CNFs due to hydrogen bonding, according high thermal stability with peak degradation occurring at 347.7 °C and quantum yield of 0.45. The nitrogen-rich surface of BNQD@CNFs exhibited strong affinity for Hg(II), quenching the fluorescence intensity due to combined inner-filter effect and photo-induced electron transfer. The limit of detection (LOD) and limit of quantification (LOQ) were 4.889 nM and 11.1 5 nM, respectively. BNQD@CNFs concomitantly exhibited adsorption of Hg(II) owing to strong electrostatic interactions, confirmed by X-ray photon spectroscopy. Presence of polar BN bonds favoured 96 % removal of Hg(II) at 10 mg L-1 with maximum adsorption capacity of 314.5 mg/ g. Parametric studies corresponded to pseudo-second order kinetics and Langmuir isotherm with R2 ≈ 0.99. BNQD@CNFs exhibited recovery rate between 101.3 %-111 % for real water samples and recyclability upto 5 cycles, demonstrating high potential in wastewater remediation.

Investigation of the antifouling properties of polyethersulfone ultrafiltration membranes by blending of boron nitride quantum dots.

This study aims to investigate the modification of polyethersulfone (PES) membrane with boron nitride quantum dots (BNQD) for improving the antifouling performance. The composite membranes were synthesized by blending different amounts of BNQD (0.50, 1.00, and 2.00 wt.%) into PES with the non-solvent induced phase separation (NIPS) method. UV-vis absorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to characterize BNQD. Moreover, porosity, pore size, contact angle, permeability, bovine serum albumin (BSA) rejection, and antifouling properties were determined for composite membranes. The enhanced biological activity of BNQD was investigated based on antioxidant, antimicrobial, anti-biofilm, bacterial viability inhibition, and DNA cleavage studies. The BNQD showed 19.35 % DPPH radical scavenging activity and 76.45 % ferrous ion chelating activity at 500 mg/L. They also exhibited good chemical nuclease activity at all concentrations. BNQD had moderate antibacterial activity against all tested microorganisms. Biofilm inhibition percentage of BNQD was determined as 82.31 % at 500 mg/L. Cell viability assay demonstrated that the BNQD showed strong cell viability inhibition 99.9 % at the concentration of 1000 mg/L. The porosity increased from 56.83 ± 1.17%-61.83 ± 1.17 % while BNQD concentration increased from 0 to 2.00 wt%. Moreover, the hydrophilicity of BNQD nanocomposite membranes also increased from 75.42 ± 0.56° to 65.34 ± 0.25°. The mean pore radius is far slightly changed from 16.47 ± 0.35 nm to 19.16 ± 0.22 nm. The water flux increased from 133.5 ± 9.5 L/m2/h (for pristine membrane) to 388.6 ± 18.8 L/m2/h (for PES/BNQD 2.00 wt% membrane). BSA flux increased from 38.8 ± 0.9 L/m2/h to 63.2 ± 2.7 L/m2/h up to 1.00 wt% amount of BNQD nanoparticles.