This review covers the fundamentals and recent developments on the mechanochemical synthesis of noble metal nanoparticles.

A series of isoniazid derivatives bearing a phenolic or heteroaromatic coupled frame were obtained by mechanochemical means. Their pH stability and their structural (conformer/isomer) analysis were checked. The activity of prepared derivatives against Mycobacterium tuberculosis cell growth was evaluated. Some compounds such as phenolic hydrazine 1a and almost all heteroaromatic ones, especially 2, 5 and 7, are more active than isoniazid, and their activity against some M. tuberculosis MDR clinical isolates was determined. Compounds 1a and 7 present a selectivity index >1400 evaluated on MRC5 human fibroblast cells. The mechanism of action of selected hydrazones was demonstrated to block mycolic acid synthesis due to InhA inhibition inside the mycobacterial cell.

Current time-resolved in situ approaches limit the scope of mechanochemical investigations possible. Here we develop a new, general approach to simultaneously follow the evolution of bulk atomic and electronic structure during a mechanochemical synthesis. This is achieved by coupling two complementary synchrotron-based X-ray methods: X-ray absorption spectroscopy (XAS) and X-ray diffraction. We apply this method to investigate the bottom-up mechanosynthesis of technologically important Au micro and nanoparticles in the presence of three different reducing agents, hydroquinone, sodium citrate, and NaBH₄. Moreover, we show how XAS offers new insight into the early stage generation of growth species (e.g. monomers and clusters), which lead to the subsequent formation of nanoparticles. These processes are beyond the detection capabilities of diffraction methods. This combined X-ray approach paves the way to new directions in mechanochemical research of advanced electronic materials.

A series of hydrazones, as potential therapeutic agents, were successfully synthesized in a vibratory ball-mill from various substituted organic hydrazines and phenol aldehydes. The degree of conversion was increased by high electronic density on the amino group of the hydrazine reactant, as well as low steric hindrance around both reactive sites. In this particular case, the flexibility of the chain bearing the amino reactive site of hydrazine was highlighted as a factor influencing the reaction rate. The results showed that hydrazones could be obtained with more than a 99% transformation, without concurring by-products. This is highly adapted to the synthesis of active pharmaceutical ingredients, requiring a high level of purity. Owing to the fact that neither an environmentally unadvisable reagent nor additives or catalysts were added to achieve the transformation, this synthesis provides a good example and a prefiguration of an efficient green pharmaceutical process.

The influence of reducing agents on the mechanochemical synthesis of Au nanoparticles differ significantly from analogous solution syntheses. Environmentally benign mechanochemical syntheses of metal nanoparticles therefore require dedicated studies.