## 2 The Present Issue  
I am deeply honored to be the guest editor of this thematic issue which includes two reviews, two communications and three papers (see the content list). I am grateful to the several leaders in these areas and would like to place on record my thanks to these illustrious contributors. I am equally thankful to many reviewers who have helped me to evaluate and critique these manuscripts with substantial improvements. I appreciate Prof. Dr. [PERSON]/Editor-in-Chief of _Applied Sciences_, for inviting me to guest edit this special issue and staff of the Applied Sciences Editorial office who supported the entire process. This issue provides access to several articles encompassing the sustainable theme. The first review article by [PERSON] and [PERSON] [19] describes elegant applications of glycerol, a non-toxic, non-hazardous, non-volatile, biodegradable, and recyclable liquid that is generated as a byproduct in the manufacture of biodiesel fuel from vegetable oils. Due to its unique chemical and physical properties and its easy availability, glycerol has emerged as an economically viable and safe solvent for organic synthesis including nanomaterials. Further, glycerol can be used as a hydrogen source in metal-catalyzed transfer hydrogenation for a variety of organic compounds [19]; the utility of glycerol as solvent and reducing agent has tremendous future potential. The second review article describes the fastest growing segment of a group of catalysts that bridge the homogeneous and heterogeneous catalysis. Magnetically recyclable nano-catalysts and their use in aqueous media for the development of sustainable organic synthesis methodologies are summarized [20]. Water is the ideal medium to perform the chemical reactions with magnetically recyclable nano-catalysts, as this fusion adds tremendous value to the overall benign reaction process development. The review highlights recent developments in the use of water and magnetically recyclable nano-catalysts for an array of organic reactions namely reduction, oxidation, condensation, and several cross-coupling reactions. Continuing on the same theme, [PERSON] _et al._ describe a water-based MW-assisted solid-phase synthesis using Boc-amino acid nanoparticles which enables a rapid solid-phase reaction of nanoparticle reactants on the resin in aqueous medium [21]. The syntheses of Leu-enkephalin, Tyr-Gly-Gly-Phe-Leu-OH, and model peptide with difficult sequence such Val-Ala-Val-Ala-Gly-OH, has been described using water-based MW-assisted protocol with Boc-amino acid nanoparticles. [PERSON] _et al._ summarize the green technologies pertaining to the photopolymerization area wherein the use of visible light sources (Xe and Hg-Xe lamps, diode lasers), soft irradiation conditions (household lamps: halogen lamp, fluorescence bulbs, LED bulbs), sunlight exposure, development of very efficient photo initiating systems and use of renewable monomers are highlighted [22]. Adhering to the principles of green chemistry, [PERSON] and [PERSON], describe a series of materials that are prepared by curing acetylated epoxidized soybean oil (AESO) and dibutyl itaconate (DBI) or ethyl cinnamate (EC) comonomers to provide examples of thermosets with a high proportion of bio-based carbon [23]; the comonomers are representative of cellulose-derived (DBI) or potentially lignin-derived (EC) raw materials. Representing the use of alternate energy activation, [PERSON] _et al._ have synthesized new 1,3-diaryl-5-(1-phenyl-3-methyl-5-chloropyrazol-4-yl)-4,5-dihydropyrazole derivatives under ultrasonic irradiation conditions in ethanol or methanol/glacial acetic acid mixture [24]. Hydrazines and several chalcone-like heteroanalogues, accessed from 5-chloro-3-methyl-1-phenyl-1_H_-pyrazole-4-carbaldehyde, are used and the method provides numerous advantages over current methodologies such as shorter reaction times (2-20 min), simple work-up procedure, and good yields.