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1. Antimicrobial activity of graphene oxide quantum dots: impacts of chemical reduction

   https://doi.org/10.1039/C9NA00698B  

   Rojas-Andrade, Mauricio D.; Nguyen, Tuan Anh; Mistler, William P.; Armas, Juan; Lu, Jia En; Roseman, Graham; Hollingsworth, William R.; Nichols, Forrest; Millhauser, Glenn L.; Ayzner, Alexander; et al (January 2020, Nanoscale Advances)

   Design and engineering of graphene-based functional nanomaterials for effective antimicrobial applications has been attracting extensive interest. In the present study, graphene oxide quantum dots (GOQDs) were prepared by chemical exfoliation of carbon fibers and exhibited apparent antimicrobial activity. Transmission electron microscopic measurements showed that the lateral length ranged from a few tens to a few hundred nanometers. Upon reduction by sodium borohydride, whereas the UV-vis absorption profile remained largely unchanged, steady-state photoluminescence measurements exhibited a marked blue-shift and increase in intensity of the emission, due to (partial) removal of phenanthroline-like structural defects within the carbon skeletons. Consistent results were obtained in Raman and time-resolved photoluminescence measurements. Interestingly, the samples exhibited apparent, but clearly different, antimicrobial activity against Staphylococcus epidermidis cells. In the dark and under photoirradiation (400 nm), the as-produced GOQDs exhibited markedly higher cytotoxicity than the chemically reduced counterparts, likely because of (i) effective removal by NaBH 4 reduction of redox-active phenanthroline-like moieties that interacted with the electron-transport chain of the bacterial cells, and (ii) diminished production of hydroxyl radicals that were potent bactericidal agents after chemical reduction as a result of increased conjugation within the carbon skeletons. 

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2. Nickel Hydroxide/Carbon Dot Nanocomposites as Effective Antibacterial Agents

   https://doi.org/10.1002/asia.202500560  

   DuBois, Davida Briana; Yu, Bingzhe; Tressel, John; Singewald, Kevin; Millhauser, Glenn L; Saltikov, Chad; Bridges, Frank; Chen, Shaowei (August 2025, Chemistry – An Asian Journal)

   Abstract Antibiotic‐resistant bacterial strains are an ever‐present hurdle for human health. A route to overcoming this threat is the development of effective antimicrobial agents based on carbon‐supported nanocomposites. In this study, carbon dots (CD) are synthesized by a facile hydrothermal treatment of ethylenediaminetetraacetic acid and melamine and further functionalized with nickel hydroxide colloids. Whereas CD alone exhibits virtually no antimicrobial activity under photoirradiation at 365 nm againstEscherichia coliin comparison to the blank control, the performance is markedly enhanced with the Ni(OH)₂‐CD nanocomposites, with the lag time prolonged from 7 to 15 h and growth rate reduced by ca. 15%. This is ascribed to the Ni(OH)₂colloids that facilitate the separation of photogenerated electron‐hole pairs and ensuing production of superoxide radicals, as confirmed by photoluminescence and electron paramagnetic resonance measurements, which induce oxidative stress and damage to the bacterial cell membranes, thereby leading to effective bactericidal activity. Consistent results are obtained in live/dead assays. Results from this work highlight the unique potential of carbon‐based composites in the development of next‐generation antimicrobial agents. 

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3. Development of 4-[4-(Anilinomethyl)-3-phenyl-pyrazol-1-yl] Benzoic Acid Derivatives as Potent Anti-Staphylococci and Anti-Enterococci Agents

   https://doi.org/10.3390/antibiotics11070939  

   Raj KC, Hansa; Gilmore, David F.; Alam, Mohammad A. (July 2022, Antibiotics)

   From a library of compounds, 11 hit antibacterial agents have been identified as potent anti-Gram-positive bacterial agents. These pyrazole derivatives are active against two groups of pathogens, staphylococci and enterococci, with minimum inhibitory concentration (MIC) values as low as 0.78 μg/mL. These potent compounds showed bactericidal action, and some were effective at inhibiting and eradicating Staphylococcus aureus and Enterococcus faecalis biofilms. Real-time biofilm inhibition by the potent compounds was studied, by using Bioscreen C. These lead compounds were also very potent against S. aureus persisters as compared to controls, gentamycin and vancomycin. In multiple passage studies, bacteria developed little resistance to these compounds (no more than 2 × MIC). The plausible mode of action of the lead compounds is the permeabilization of the cell membrane determined by flow cytometry and protein leakage assays. With the detailed antimicrobial studies, both in planktonic and biofilm contexts, some of these potent compounds have the potential for further antimicrobial drug development. 

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4. First synthesis of 2D materials by hypergolic reactions and evaluation of their dispersions for ink formulation: hexagonal boron nitride and fluorinated carbon nanosheets

   https://doi.org/10.1088/2053-1591/ad2d42  

   Chalmpes, Nikolaos; Bourlinos, Athanasios B; Alsmaeil, Ahmed Wasel; Aljarrah, Abdulaziz S; Salmas, Constantinos E; Karakassides, Michael A; Giannelis, Emmanuel P (March 2024, Materials Research Express)

   Abstract Hypergolic reactions have emerged as a new synthetic approach enabling the rapid production of a diverse set of materials at ambient conditions. While hypergolic reactions bear several similarities to the well-established flame spray pyrolysis (FSP), the former has only recently been demonstrated as a viable approach to materials synthesis. Here we demonstrate a new pathway to 2D materials using hypergolic reactions and expand the gallery of nanomaterials synthesized hypergolically. More specifically, we demonstrate that ammonia borane complex, NH₃BH₃, or 4-fluoroaniline can react hypergolically with fuming nitric acid to form hexagonal boron nitride/fluorinated carbon nanosheets, respectively. Structural and chemical features were confirmed with x-ray diffraction, infrared, Raman, XPS spectroscopies and N₂porosimetry measurements. Electron microscopy (SEM and TEM) along with atomic force microscopy (AFM) were used to characterize the morphology of the materials. Finally, we applied Hansen affinity parameters to quantify the surface/interfacial properties using their dispersibility in solvents. Of the solvents tested, ethylene glycol and ethanol exhibited the most stable dispersions of hexagonal boron nitride (h-BN). With respect to fluorinated carbon (FC) nanosheets, the suitable solvents for high stability dispersions were dimethylsulfoxide and 2-propanol. The dispersibility was quantified in terms of Hansen affinity parameters (δ_d,δ_p,δ_h) = (16.6, 8.2, 21.3) and (17.4, 10.1, 14.5) MPa^1/2for h-BN and FC, respectively. 

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5. Synthesis and Antibacterial Evaluation of Silver-Coated Magnetic Iron Oxide/Activated Carbon Nanoparticles Derived from Hibiscus esculentus

   https://doi.org/10.3390/magnetochemistry11070053  

   Güneş, Müslüm; Ertaş, Erdal; Tumur, Seyhmus; Zulfugarova, Parvin; Nuriyeva, Fidan; Kavetskyy, Taras; Kukhazh, Yuliia; Grozdov, Pavlo; Šauša, Ondrej; Smutok, Oleh; et al (July 2025, Magnetochemistry)

   The increasing prevalence of antimicrobial resistance alongside the pharmacological limitations and adverse effects associated with conventional antibiotics necessitates the development of novel and efficacious antimicrobial agents. In this study, magnetic iron oxide nanoparticles (MIONPs) were synthesized via a chemical co-precipitation method. Activated carbon (AC) derived from Hibiscus esculentus (HE) fruit was coated onto the nanoparticle surfaces to fabricate MIONPs/HEAC nanocomposites. To augment their antimicrobial properties, silver ions were chemically reduced and deposited onto the MIONPs/HEAC surface, yielding MIONPs/HEAC@Ag nanocomposites. Comprehensive characterization of the synthesized nanocomposites was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), dynamic light scattering (DLS), and zeta potential analysis. DLS measurements indicated average particle sizes of approximately 122 nm and 164 nm for MIONPs/HEAC and MIONPs/HEAC@Ag, respectively. Saturation magnetization values were determined to be 73.6 emu/g for MIONPs and 65.5 emu/g for MIONPs/HEAC. Antibacterial assays demonstrated that MIONPs/HEAC@Ag exhibited significant inhibitory effects against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, with inhibition zone diameters of 11.50 mm and 13.00 mm, respectively. In contrast, uncoated MIONPs/HEAC showed negligible antibacterial activity against both bacterial strains. These findings indicate that MIONPs/HEAC@Ag nanocomposites possess considerable potential as antimicrobial agents for biomedical applications, particularly in addressing infections caused by antibiotic-resistant bacteria. 

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