Promising nanotechnological platforms, based on inorganic nanoparticles and nanomaterials, have emerged in such fields as targeted drug delivery, bio- and chemical sensing, catalysis, antimicrobial coatings, and optoelectronic devices, among others. However, concerns regarding the sustainability of physicochemically-synthesized nanomaterials, which often require energy-intensive processes, high temperatures, toxic solvents or undesirable chemical wastes, have also emerged. Researchers have therefore looked to replace chemical syntheses by sustainable and environmentally friendly techniques. Biosynthesis of nanomaterials, i.e., the use of living organisms, their components, extracts or biomolecules, as catalysts for the sustainable production of nanomaterials, has experienced a tremendous expansion during the last two decades. Among these production platforms, the roles of algae have attracted increasing attention from research scientists worldwide. The aim of the present review, the first of its kind, is to provide important information to readers regarding the diversity of algal strains exploited in the booming field of nanobiotechnology and green chemistry, the various methodologies through which these diverse organisms are used, the variety of fabricated nanomaterials composed of noble metals, oxides and chalcogenides, and the significance of the large range of sizes and shapes of these nanomaterials that confer to them unique properties desirable for specific bio-applications.

The ability to produce low-cost, hierarchically-structured and nanopatterned inorganic materials could potentially revolutionize the way we fabricate photovoltaic, energy storage, and optoelectronic devices. In nature, many organisms carry out the hierarchical assembly of metal oxide materials through cellular and biochemical processes that replicate periodic micro- and nanoscale features by a bottom-up approach at ambient conditions. For example, single-celled algae called diatoms produce a nanostructured amorphous silica skeleton called a frustule. The insertion of other metal oxide materials such as titanium or germanium dioxide into the nanostructure of the diatom frustule could potentially be utilized to fabricate new dye-sensitized solar cells, nanostructured battery electrodes, and electroluminescent display devices. The exploitation of diatom nanobiotechnology for the development of novel device concepts in these areas is overviewed.

The synthesis and assembly of nanoparticles using green technology has been an excellent option in nanotechnology because they are easy to implement, cost-efficient, eco-friendly, risk-free, and amenable to scaling up. They also do not require sophisticated equipment nor well-trained professionals. Bionanotechnology involves various biological systems as suitable nanofactories, including biomolecules, bacteria, fungi, yeasts, and plants. Biologically inspired nanomaterial fabrication approaches have shown great potential to interconnect microbial or plant extract biotechnology and nanotechnology. The present article extensively reviews the eco-friendly production of metalloid nanoparticles, namely made of selenium (SeNPs) and tellurium (TeNPs), using various microorganisms, such as bacteria and fungi, and plants’ extracts. It also discusses the methodologies followed by materials scientists and highlights the impact of the experimental sets on the outcomes and shed light on the underlying mechanisms. Moreover, it features the unique properties displayed by these biogenic nanoparticles for a large range of emerging applications in medicine, agriculture, bioengineering, and bioremediation.

Nanomaterials have supported important technological advances due to their unique properties and their applicability in various fields, such as biomedicine, catalysis, environment, energy, and electronics. This has triggered a tremendous increase in their demand. In turn, materials scientists have sought facile methods to produce nanomaterials of desired features, i.e., morphology, composition, colloidal stability, and surface chemistry, as these determine the targeted application. The advent of photoprocesses has enabled the easy, fast, scalable, and cost- and energy-effective production of metallic nanoparticles of controlled properties without the use of harmful reagents or sophisticated equipment. Herein, we overview the synthesis of gold and silver nanoparticles via photochemical routes. We extensively discuss the effect of varying the experimental parameters, such as the pH, exposure time, and source of irradiation, the use or not of reductants and surfactants, reagents’ nature and concentration, on the outcomes of these noble nanoparticles, namely, their size, shape, and colloidal stability. The hypothetical mechanisms that govern these green processes are discussed whenever available. Finally, we mention their applications and insights for future developments.