Modern trends in the greener synthesis and fabrication of inorganic, organic and coordination compounds, materials, nanomaterials, hybrids and nanocomposites are discussed. Green chemistry deals with synthesis procedures according to its classic 12 principles, contributing to the sustainability of chemical processes, energy savings, lesser toxicity of reagents and final products, lesser damage to the environment and human health, decreasing the risk of global overheating, and more rational use of natural resources and agricultural wastes. Greener techniques have been applied to synthesize both well-known chemical compounds by more sustainable routes and completely new materials. A range of nanosized materials and composites can be produced by greener routes, including nanoparticles of metals, non-metals, their oxides and salts, aerogels or quantum dots. At the same time, such classic materials as cement, ceramics, adsorbents, polymers, bioplastics and biocomposites can be improved or obtained by cleaner processes. Several non-contaminating physical methods, such as microwave heating, ultrasound-assisted and hydrothermal processes or ball milling, frequently in combination with the use of natural precursors, are of major importance in the greener synthesis, as well as solventless and biosynthesis techniques. Non-hazardous solvents including ionic liquids, use of plant extracts, fungi, yeasts, bacteria and viruses are also discussed in relation with materials fabrication. Availability, necessity and profitability of scaling up green processes are discussed.

No abstract

An important reason for the relatively low efficiency of dye-sensitized solar cells (DSSCs) is the low open-circuit voltage (V OC) of about 0.7 V for a standard solar cell with a dye that has an absorption onset at 1.6 eV. We report an enhancement of the V OC of about 0.10 V with respect to a TiO2-based DSSC modified with ZnO nanoflowers that we prepared by a new and facile method. An additional increase of the V OC of about 0.08 V was achieved by modifying the ZnO nanoflowers with Au nanoparticles, resulting in a DSSC with an efficiency of 2.79%, highlighted by a high V OC of 0.89 V. Detailed analysis with electrochemical impedance spectroscopy and intensity-modulated photovoltage and photocurrent spectroscopies (IMVS and IMPS) reveal that the main reason for the increase of V OC is related to the shift of the band edges upon coupling TiO2 with ZnO nanoflowers, even though the electron lifetime at the same charge density actually decreases. These results show the intricate interplay between band edge shift, recombination kinetics, and DSSC performance and illustrate that a higher voltage DSSC can be fabricated by modification of the photoanode materials.

No abstract

In this study, silver nanoparticles (NP) were synthesized by two methods: using an aqueous extract of Mentha spicata leaves and using citrate ions as stabilizing agent, and the cytotoxicity and anticancer activity of both NP were evaluated in vitro. The particles synthesized with the aqueous extract were spherical with a size ranging from 15 to 45 nm. These NP decreased cell viability in all of the cells studied; however, the IC50 could only be estimated in the Chang liver cells (IC50 = 21.37 µg/mL). These particles also decreased the generation of reactive oxygen species in Chang and SiHa cells. Additionally, the dispersions decreased the activity of caspase-3. There was no significant difference between the biological activities of the NP obtained with the aqueous extract and the NP synthesized using citrate ions. This study showed that an aqueous extract of M. spicata is an excellent alternative for the synthesis of silver NP. These NP showed cytotoxicity and anticancer activity in vitro. Although more experiments are required, the cell death occurs probably through a mechanism different from apoptosis.