If you wrap a toxic core with a non-toxic shell the result is a non-toxic NP....at least until the outer shell is breached. So Au over a CdSe NP would be an example of this.
“Quantum dot toxicity depends on exposure time, particle size, and concentration. They are more toxic, the longer they are in contact with something, the smaller the particles are, and the higher their concentration. The smaller the quantum dot particle size, the larger the specific surface area, and the more exposed core, the freer ion production and toxicity[69].
Non-shell CdSe QD is a pollutant in the environment that can cause serious health problems, very dangerous to aquatic life, also causes oxidative stress, endoplasmic reticulum stress, inflammation, and genomic instability , make a lot of reactive oxygen species, cause autophagy, seriously harm DNA, and so on [70]–[73]. CdSe QDs without a shell can't be replaced right now because of how well they glow. Because of this, it might be a good idea to think about lowering its cytotoxicity or looking for alternatives, such as core/shell based CdSe QDs.
Core/shell QD is a nanoscale-based structure generated by one nanomaterial surrounding another nanomaterial by chemical bond or other force. Chemical composition of the QD core and shell affects ultimate cytotoxicity. By choosing different shells, structure, shape, and spectral properties of quantum dots can be changed. Thickening the core-shell structure changes its emission peak and optical characteristics. This metal and non-metal coating may increase the fluorescence characteristics of quantum dots, inhibit contact between the nucleus' metallic core and the environment, minimize leakage and free ion production, and reduce toxicity [73]. So, wrapping a toxic CdSe QD core with a non-toxic shell, the result is a non-toxic QD. For example, low toxicity and ease production make ZnS the most prevalent shell form[74]. R.K. Ratnesh et al. [75] observed that core-shell (CdSe/ZnS) has been shown to have higher viability and less toxic than core CdSe. The toxicity of CdSe/CdS is between twos, as is their viability[75]. Colloidal QDs of multinary I-III-VI have a high potential to replace the highly toxic, heavy metal-based CdSe QDs, because of high absorption coefficients and narrow bandgaps [76], for example CdSe/CdS/ZnS [77], CdTe/CdSe/ZnSe [78] etc
Article Microbial synthesis of Cadmium selenide quantum dots (CdSe Q...
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