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Highly fluorescent copper nanoclusters (Cu NCs) have been synthesized using single-step reduction of copper sulfate by hydrazine in the presence of lysozyme. The fluorescence quantum yield was measured to be as high as 18%. The emission was also found to be dependent on the excitation wavelength. Mass spectrometric analyses indicated the presence of species corresponding to Cu2 to Cu9. Transmission electron microscopic analyses indicated the formation of agglomerated particles of average diameter of 2.3 nm, which were constituted of smaller particles of average diameter of 0.96 nm. They were found to be stable between pH 4 and 10 and in addition having excellent chemical and photostability. The noncytotoxic NCs were used to successfully label cervical cancer HeLa cells.

Advanced theranostic materials hold promise for targeted delivery of drugs, with the ability to follow the transport as well as its consequences. This should, ideally, be possible with minimum invasive surgery and having no or minimum cytotoxicity of the materials. It requires development of newer materials whose physical properties would allow for easy probe, which could carry the therapeutic molecules, which will be stable under physiological conditions, and at the same time would be able to permeate barriers to the target. We report the development of a composite consisting of highly fluorescent Au nanoclusters and the biopolymer chitosan, which could easily be converted into nanoparticles and would form a stable polyplex with suicide gene for induction of apoptosis in cervical cancer cells. The simultaneous red, green, and blue fluorescence from the nanoclusters provided convenient optical imaging and flow cytometry probes, without having to use additional dyes. Moreover, the colloidal nanocluster-polymer composite could be converted into solid film and be stored with the retention of optical properties. The pH tunable optical properties in the medium were also intact in the films that quickly dissolved in water with retention of properties.

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Herein, different surface charged carbon dots (Cdots) were synthesized by using diethylene glycol as a carbon source with various amine containing surface passivating agents. The synthesis method is very simple and fast microwave oven-based, that results in almost similar sized positive, negative and uncharged fluorescent Cdots which has been confirmed by zeta potential analysis in our case. The formation of Cdots was confirmed by characterization using fluorescence spectroscopy, transmission electron microscopy, XRD, FT-IR, and XPS spectroscopy. To find out relative bactericidal activity of these Cdots, green fluorescence protein expressing recombinant E. coli bacteria were taken as a model system. Time-dependent bacterial growth and FACS study demonstrated that both uncharged Cdots and positively charged Cdots were showing better bactericidal activity as compared to negative charged Cdots. The Cdots caused elevation of reactive oxygen species level, which is possibly leading to bacterial cell death.