The term aerogel is used for unique solid-state structures composed of three-dimensional (3D) interconnected networks filled with a huge amount of air. These air-filled pores enhance the physicochemical properties and the structural characteristics in macroscale as well as integrate typical characteristics of aerogels, e.g., low density, high porosity and some specific properties of their constituents. These characteristics equip aerogels for highly sensitive and highly selective sensing and energy materials, e.g., biosensors, gas sensors, pressure and strain sensors, supercapacitors, catalysts and ion batteries, etc. In recent years, considerable research efforts are devoted towards the applications of aerogels and promising results have been achieved and reported. In this thematic issue, ground-breaking and recent advances in the field of biomedical, energy and sensing are presented and discussed in detail. In addition, some other perspectives and recent challenges for the synthesis of high performance and low-cost aerogels and their applications are also summarized.

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In this study, selective green synthesis of gold nanoparticles (nAu) with the use of Tarragon extract (Artemisia dracunculus) was investigated. Characterization of the synthetized nAu was carried out using several techniques including: UV-Vis, SEM, zeta potential analysis, DLS, and ATR-FTIR. Based on measurements of Tarragon extract by HPLC-MS, significant chemical substances participating as reducing and stabilizing agents were identified. FTIR confirmed typical functional groups that could be found in these acids on the nAu surface, such as O-H, C=O and C-O. The effects of various parameters (concentration of Tarragon extract, Au precursor, and initial pH of the synthesis) on the shape and size of the nanoparticles have been investigated. UV-Vis and SEM confirmed the formation of nAu at various concentrations of the extract and Au precursor and showed correlation between the added extract concentration and shift in maximal absorbance towards higher frequencies, indicating the formation of smaller nanoplates. Zeta potential determined at various pH levels revealed that its value decreased with pH, but for all experiments in the pH range of 2.8 to 5.0, the value is below - 30 mV, an absolute value high enough for long-term nAu stability. In order to evaluate nAu catalytic activity, the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model system. The reaction takes place 1.5 times faster on Au-triangles than on Au-spherical NPs.

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We investigated the antioxidant properties of detonation nanodiamond modified by Fenton's reagent. Diamond nanoparticles functionalized with hydroxyl groups were examined in soybean oil; the aim of this study was to determine their antioxidant properties by examining the effect on the lipid peroxidation process. In order to form the hydroxyl groups on the surface of the detonation diamond nanoparticles we utilized the Fenton reaction. This reaction consisted of the oxidation of the surfaces of the nanodiamonds by the reaction of Fe 2+ with hydrogen peroxide (H 2 O 2 ), which is a precursor of the hydroxyl radical. The oxidation reaction of nanodiamonds via Fenton's reagent is twofold, in addition to surface oxidation it is also purified from different carbon varieties. We traced the impact of the modified nanodiamonds on the oxidation process of soybean oil. In order to hasten the process of lipid peroxidation the soybean oil was exposure to UV light with a wavelength of 250 nm. Analysis was performed before and after 3, 6,9,24, 48 and 72 hours of exposure to UV light. Comparing the results of pure oil and oil with the addition of functionalized powder, we noted a significant impact of the modified nanodiamond compared to non-modified nanodiamond on the process of counteracting the rancidity of the oil. This observation was confirmed by the peroxide value, anisidine value, Totox index and Kreis test.