Pseudomonas aeruginosa (P. aeruginosa) is one of the common immortal pathogens that cause intense chronic infections in low-immunity patients, significantly evading the immune system and suppressing the respiratory system. This work reports on the synthesis of prominent members of the carbon family, carbon quantum dots (CQDs), from a natural carbon precursor, Citrus medica (C. medica) fruit, and their inhibiting property against P. aeruginosa. CQDs synthesized by the conventional hydrothermal method with an average particle size of 4.5 nm exhibit renowned antimicrobial properties. To enhance the properties of the CQDs, nitrogen was doped using ammonium hydroxide as a nitrogen source, and absorption and fluorescence studies and the elemental composition of CQDs were also reported. CQDs potentially inhibited the growth of bacteria at the lowest concentration level of 1.25% (v/v). Similarly, CQDs moderately inhibited biofilm formation at the concentration level of 0.07% (v/v) for both clinical and control strains of P. aeruginosa. A fluorescence microscopy study revealed that the treated strain shows a moderately reduced biofilm formation when compared to the control strain of P. aeruginosa PAO1.

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In the present study, the nanostructured ternary hybrid composite of rGO/Mn 3 O 4 /MoO 3 has been synthesized for photocatalytic studies investigated in visible light. The graphene oxide, rGO/Mn 3 O 4, and rGO/Mn 3 O 4 /MoO 3 nanocomposites were prepared by using the modified Hummers' method, co-precipitation method, and hydrothermal method respectively. Organic dyes such as methylene blue and methylene violet were used for the degradation process. In rGO/Mn 3 O 4 /MoO 3 hybrid, graphene oxide (GO) acts as an excellent electron conductor and manganese oxide (Mn 3 O 4 ) decomposes the dye molecules within a short time. Molybdenum trioxide (MoO 3 ) shows good photocatalytic activity towards organic pollutants as well as promotes oxygen evolution reaction. The physiochemical characterizations such as X-ray diffraction, field emission scanning electron microscopy, energydispersive X-ray spectroscopy (EDX), FT-IR, and UV-vis spectroscopy analysis were carried out. Furthermore, the photocatalytic efficiency of the as-synthesized ternary composite was recorded as 95% which is much higher than the efficiency of individual components due to the synergetic effect of rGO. Two-dimensional structured GO increases the absorption sites which act as charge trapping centers which help to reduce electron-hole recombination effect. Photodegradation mechanism of methylene blue and methylene violet dyes for wastewater treatment application under ambient conditions has been discussed.

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