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    Biomass valorization of liquid whey into carbon quantum dots via hydrothermal process for food pathogenic bactericidal activity and photocatalytic degradation of brilliant red dye
    (Elsevier, 2024) Thakur, Sweezee; Bains, Aarti; Kumar, Anil; Goksen, Gulden; Yaqoob, Mudasir; Parvez, Mohammad Khalid; Al-Dosari, Mohammed S.
    Whey is the primary waste material of the dairy industries; therefore, the present study focuses on the valorization of milk processing industry-originated liquid whey into valuable products, specifically liquid whey carbon quantum dots (LW-CQDs) for pathogenic bactericidal and photocatalytic dye reduction efficacy. Facile synthesis of fluorescent LW-CQDs was carried out by employing a green hydrothermal approach at 200 degrees C for 12 h. Several analytical techniques were used to confirm the thermally stable spherical particles, measuring 9.04 +/- 0.76 nm size in diameter, primarily composed of carbon and oxygen LW-CQDs. The presence of diverse functional groups (hydroxyl, carboxyl, carbonyl, and methyl groups) of LW-CQDs contributed to overall optical properties, which manifested a blue emission peak at 418 nm with 240 nm excitation wavelength in fluorescence spectroscopy. UV-Visible spectra featured two peaks (pi -> pi * transition of C = C bonds and n -> pi * transition of C = O bonds) at around 249 and 293 nm, respectively. Moreover, the synthesized LW-CQDs exhibited a significantly higher zone of inhibition (25.98 +/- 0.17 mm) and significantly lower minimum inhibitory concentration (4.47 +/- 0.01 mu l/ml) against the Staphylococcus aureus. In addition, LW-CQDs revealed a higher killing rate of reaction for S. aureus as compared to K. pneumoniae, P. aeruginosa, and S. typhi and remarkably degraded 92.95 % of brilliant red dye under visible light (2000 lux). Hence, these facile LW-CQDs hold potential for applications in the effectiveness of antimicrobial and photocatalytic dye reduction activity, which show valuable contributions to both waste valorization and sustainable material development.
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    Biomass-derived carbon quantum dots from C hlorella vulgaris: Photocatalytic reduction of malachite green dye coupled with anti-quorum sensing and antimicrobial activity against food pathogens
    (Elsevier, 2024) Thakur, Sweezee; Bains, Aarti; Kumar, Anil; Goksen, Gulden; Dhull, Sanju Bala; Ali, Nemat; Khan, Mohammad Rashid
    Algae, particularly Chlorella vulgaris, , present a novel, sustainable source for producing carbon quantum dots (CQDs) with unique properties. This study introduces an eco-friendly synthesis method using a hydrothermal process at 200 degrees C for 12 h, yielding stable, spherical CQDs with an average diameter of 7.19 +/- 0.06 nm, composed primarily of carbon and oxygen. The innovation consists on employing microalgal biomass for the production of CQDs, hence obviating the necessity for additional chemicals or passivating agents. The CQDs exhibit a fluorescence peak at 416 nm upon excitation at 241 nm, with UV-visible spectra showing pi ->pi* and n ->pi* transition at 241 nm and 356 nm, respectively. High-resolution TEM analysis reveals a crystalline structure with a 0.21 nm interlayer spacing, confirmed by lattice fringes, and a quantum yield of 41.24%, indicating efficient photoluminescence. The CQDs demonstrate strong antimicrobial activity against pathogens like Staphylococcus aureus and Pseudomonas aeruginosa, , with significant inhibition of quorum sensing like twitching and swarming and bacterial motilities. Furthermore, the CQDs achieve a 91.47% degradation of malachite green dye, underscoring their potential in environmental remediation. This study highlights the dual applications of Chlorella vulgaris-derived CQDs in health and environmental contexts, presenting a sustainable and innovative approach for nanomaterial synthesis.
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    Synthesis of hydrothermal-assisted papaya peel-derived carbon quantum dots impregnated carboxymethyl cellulose and pectin crosslinked nanohydrogel for shelf-life enhancement of strawberry
    (Elsevier, 2024) Thakur, Sweezee; Bains, Aarti; Kumar, Anil; Goksen, Gulden; Dhull, Sanju Bala; Ali, Nemat; Kaushik, Ravinder
    This study focuses on utilizing papaya peel to produce carbon quantum dots (PP-CQDs) via a hydrothermal method and the PP-CQDs are subsequently embedded into carboxymethyl cellulose and pectin nanohydrogel to enhance the shelf-life of strawberries. The synthesis of PP-CQDs was found to be optimal under conditions of 12 h and 200 degrees C, resulting in a quantum yield of 39.15% and an average particle size of 4.16+0.07 nm. The PP-CQDs had intense blue luminescence and a peak absorbance at 262 nm when exposed to UV light. They also displayed unique fluorescence emission at 260 nm and excitation at 526 nm. Particle size was not significant for both control (176.4 + 0.18 nm) and PP-CQDs embedded nanohydrogel (175.8 + 0.09 nm). The PP-CQDs nanohydrogel composite demonstrated high cell viability (95.12+0.78 to 98.43+0.96 %) as well as excellent antibacterial efficacy against pathogenic Staphylococcus aureus bacteria during time-kill and anti-quorum activity. Both types of coated strawberries exhibited non-significant differences in weight loss (16.85+0.18 and 16.34 +0.39 %) as compared to uncoated strawberries (20.87+0.42 %) during storage. The firmness of both coated strawberries was found to be significantly higher as compared to uncoated samples, while strawberries coated with composite nanohydrogel showed enhanced microbial stability. Overall, PP-CQDs embedded nanohydrogel could be a promising coating material to enhance the shelf-life of highly perishable fruits.