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Trimanganese tetraoxide (Mn3O4)−silver (Ag) nanocomposites have been synthesized by seed‐mediated growth of manganese oxide by alkaline hydrolysis of manganese precursor on preformed silver nanoparticles at water/n‐heptane interface. The morphology of the nanocomposites has been varied by individual addition of five size‐selective silver nanoparticles for the evolution of the manganese components. Varieties of spectroscopic and microscopic techniques have been used to characterize these materials. Now, the efficacy of these as‐synthesized nanocomposites has been demonstrated towards the sensing of various hazardous volatile organic compounds, exhibiting high sensitivity to ethanol compared to other components. Moreover, the structure‐function relationship of the Mn3O4−Ag nanocomposites upon variation of the size of silver particles towards the sensory activity of ethanol has been elucidated.

Hierarchical porous carbon nanospheres were synthesized by a hydrothermal process at 130 °C/24 h using different triblock copolymers such as F108 (PEO133PPO50PEO133; PEO, poly­(ethylene oxide); PPO, poly­(propylene oxide)), F127 (PEO106PPO70PEO106), and L64 (PEO13PPO30PEO13) as soft templating agents. Characterization of the samples was carried out by low angle XRD, Raman spectra, FESEM, TEM, and N2 adsorption–desorption studies. The BET surface area of the samples was in the range 600–750 m2/g comprised of micropores and mesopores. Nanospherical particles of size range 60–100 nm were formed. The synthesized samples were used for the removal of phenol and methylene blue (MB), the toxic organic contaminant in water. The maximum adsorptions of 98.9 and 100% were observed within 10 min for phenol and MB, respectively. For different soft templates, the adsorption capacity of the samples followed in the order CF108 > CF127 > CL64, which was affected by the textural properties of the corresponding samples. Selective adsorption of the samples was also studied in the presence of both pollutants, phenol and MB.

In the presence of melamine and block copolymers, namely, F108, F127, and P123, nitrogen-doped nanoporous carbon nanospheroids (N@CNSs) were synthesized by the hydrothermal process. The F127-modified sample (CNF127) exhibits the maximum Brunauer–Emmett–Teller (BET) surface area of 773.4 m 2 /g with a pore volume of 0.877 cm 3 /g. The microstructural study reveals that nanospheroids of size 50–200 nm were aggregated together to form a chainlike structure for all triblock copolymer-modified samples. The X-ray photoelectron spectroscopy study shows the binding energies of 398.33 and 400.7 eV attributed to sp 2 (C–N=C)- and sp 3 (C–N)-hybridized nitrogen-bonded carbons, respectively. The synthesized N@CNS samples showed selective adsorption of organic dye methylene blue (MB) in the presence of methyl orange (MO) as well as Pb(II) ion removal from contaminated water. The adsorptions for MB and Pb(II) ions followed pseudo-first-order and pseudo-second-order kinetic models, respectively. The sample CNF127 showed the highest adsorption of 73 and 99.82 mg/g for MB and Pb(II) adsorptions, respectively. The adsorption capacity for MB of the copolymer-modified samples follows the order CNF127 > CNP123 > CNF108, which corroborated with the mesoporosity as well as nitrogen content of the corresponding samples. The maximum % adsorption of Pb(II) follows the order CNF127 (99.82%) > CNF108 (98.74%) > CNP123 (91.82%), and this trend is attributed to the BET surface area of the corresponding samples. This study demonstrates multicomponent removal of water pollutants, both organic dyes and inorganic toxic metal ions.

Mesoporous alumina (MA) was prepared via the sol−gel process at 40 °C/48 h followed by calcinations at 550 °C/5 h, in the absence of organic acids and in the presence of malic, tartaric, and citric acids (sample IDs: A-550, AM-550, respectively). For fluoride ion adsorption on MA, the effects of different parameters such as contact time, concentration of adsorbate (F − ions), pH, temperature, and competing ions were studied. The adsorption kinetics of fluoride ions followed the pseudo-second-order model. The prepared MA showed the maximum F − ions adsorption capacity of 47.2, 49, 51.2, and 62.5 mg g −1 for the samples A-550, AM-550, AT-550, and AC-550, respectively. The adsorption efficiency of MA followed the order AC-550 > AT-550 > AM-550 > A-550, corroborating to their BET surface area and pore volume. The competing anions (PO 4 3− , Cl − and SO 4 2− ) have a slight effect of reducing the F − ions adsoption in the order of PO 4 3− > SO 4 2− > Cl − . For interpretation of adsorption isotherms, both Langmuir and Freundlich models were used. The F − ions adsorption efficiency remained almost the same up to 3 cycles of the regenerated MA.

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