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Herein we report a very simple ‘mix and heat’ synthesis of a very fine Rh-nanoparticle loaded carbon fullerene-C60 nanocatalyst (Rh(0)NPs/Fullerene-C60) for the very first time. The preparation method used no reducing agent and capping agent to control the morphology of the nanocatalyst. Transmission electron microscopy (TEM) results confirmed the uniform decoration of small Rh-nanoparticles on the surface of fullerene-C60. The Rh-content in Rh(0)NPs/Fullerene-C60 was found to be 2.89 wt%. The crystalline properties of Rh(0)NPs/Fullerene-C60 were studied by X-ray diffraction (XRD). The metallic state of Rh-nanoparticles in Rh(0)NPs/Fullerene-C60 was confirmed by X-ray photoemission spectroscopy (XPS). Raman results depicted good interaction between Rh-nanoparticles and fullerene-C60. To our delight, the present Rh(0)NPs/Fullerene-C60 showed excellent catalytic activity in the reduction of 4-nitrophenol with NaBH4 in water. Very high kapp, k′ and TOF values of 82.14 × 10−3 min−1, 4107 × 10−3 min−1 and 138 min−1, respectively, were calculated for the Rh(0)NPs/Fullerene-C60 catalyzed reduction of 4-nitrophenol. To the best of our knowledge, this is the most efficient fullerene-based nanocatalyst for the rapid reduction of 4-nitrophenol reported to date. Moreover, the catalytic activity of Rh(0)NPs/Fullerene-C60 was also tested towards Suzuki cross-coupling reactions. Reusability of the Rh(0)NPs/Fullerene-C60 was also tested.

Nowadays, nanocomposites functionalized with carbonaceous–polymers, clays, noble metal, and various metal oxides play a major role in numerous applications such as in medicine, energy, sensors, heterogenous catalysis, and eco-friendly remediation. The main advantages of functional nanocomposites are their rapid and selective absorption, and their exceptional stability and recyclability, properties that are very useful for environmental remediation such as groundwater treatment. The degradation as well as removal of transition metal ions and organic pollutants from groundwater and wastewater are the most investigated subject area. The demand for such metal-based hybrid nanocomposites is increasing. Consequently, the development of highly efficient metal-based hybrid nanocomposites has attracted very special interest. In this chapter, we discuss the key innovations and developments in functional nanocomposites over the last few years. In particular, the chapter focuses on the efficient preparation of the various novel metal-based hybrid nanocomposites for environmental wastewater treatment.

The green synthesis of nanocomposites has attracted huge consideration in recent years due to its positive environmentally friendly impact. The present study reports the first bimetallic Ag–Au cellulose nanofiber composite (Ag@Au/CNCs) prepared via a very simple green preparation method. An aqueous leaves extract of Moringa oleifera was used to obtain the bimetallic Ag@Au/CNC nanocomposite. High-resolution transmission electron microscopy (HRTEM) observations revealed the successful formation of triangle, hexagonal, and spherical shapes of well-combined Ag–Au nanoparticles on the regenerated cellulose nanofiber surface. Further, the formation of Au–Ag bimetallic nanostructures was confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray crystallography (XRD) results. The resultant bimetallic Ag@Au/CNC catalyst was found to perform remarkably well in the reduction of nitrophenols. The bimetallic Ag@Au/CNC catalyst gave excellent kapp values of 15.59 and 22.83 × 10−3 s−1 for the 2- and 4-nitrophenol reduction process, respectively. To our delight, the Ag@Au/CNC catalyst was found to perform well in the aza-Michael reaction. The catalytic activity of Ag@Au/CNCs was compared with mono-metallic Ag/CNCs, Au/CNCs, and other reported catalysts. Based on the results obtained, the high synergy of Ag@Au/CNCs was explained. A possible mechanism is proposed for the Ag@Au/CNC-catalyzed nitrophenol reduction and aza-Michael reactions.

The fabrication of polymer nanocomposites based on polycaprolactone (PCL) and Titanium dioxide (TiO2) nanoparticles was successfully carried out via solution casting technique. The structural properties of prepared nanocomposites such as lattice parameters, crystallite size etc have been studied by X-ray diffraction (XRD), the interactions between PCL and TiO2 was confirmed by Fourier transform infrared (FT-IR) spectroscopy and surface morphology was evaluated by field emission scanning electron microscope (FE-SEM) analysis. In this study, the inorganic nanofiller TiO2 was successfully incorporated in PCL matrix with different weight percentage such as 1, 3 and 5 wt%. The electrical properties of the corresponding nanocomposites (PCL + 1% TiO2, PCL + 3% TiO2 and PCL + 5% TiO2) were investigated and showed good results when compared to pure PCL. The dielectric constant, dielectric loss, electric modulus and electrical conductivity were measured in the frequency range of 10−2 to 107 Hz.

Highly efficient nanocomposites (Ag/HHP and Ru/HHP) of Ag and Ru nanoparticles (NPs) supported on human hair powder (HHP) were prepared for reduction of 4-nitrophenol (4-NP) to 4-aminophenol. Ag/HHP and Ru/HHP worked well for reduction of 4-NP with faster reaction rate, exhibiting best rate constant (k app) of 5.94 × 10−2 s−1 and 6.12 × 10−2 s−1, respectively. To the best of the authors’ knowledge, these are the most efficient nanocatalysts for reduction of 4-NP reported to date. Both Ag/HHP and Ru/HHP could be reused without significant loss in catalytic activity; the physicochemical stability of Ag/HHP and Ru/HHP (after 10th use) was found to be excellent. A mechanism for the catalytic reduction of 4-NP is proposed, and the catalytic activity of the present materials is compared with previously reported results.

A novel two-phase polymer nanocomposite comprising polycaprolactone (PCL) and nanocrystalline multiferroic BiFeO3 (BFO NPs) has been fabricated by a simple casting technique. We have developed a new Schiff base ligand–Ti(IV) catalyst based on tridentate ONO chiral amino alcohol, which has been derived from salicylaldehyde. This catalyst plays a vital role in the ring opening polymerization (ROP) of cyclic esters such as e-caprolactone (e-CL). Nanocomposites consisting of multiferroic BFO NPs and insulating PCL have been prepared. It was found that the prepared nanocomposites PCL/BFO/1 wt% and PCL/BFO/3 wt% exhibit ferroelectric properties and reduced leakage of current density. Dielectric data were analyzed using the complex permittivity and complex electric modulus for the nanocomposites at room temperature. An improved AC conductivity for the PCL/BFO nanocomposites was observed compared to the pure PCL and BFO samples.

Hexagonal molybdenum oxide (h-MoO3) nanocrystals with a flower-like hierarchical structure were successfully incorporated into polycaprolactone (PCL) matrix by a simple solution casting technique. Initially, the PCL was prepared by a catalytic ring-opening polymerization (ROP) of e-caprolactone (e-CL) under solvent free condition. Thiosemicarbazide and 4-phenylthiosemicarbazide based metal (Zn2+ and Cu2+) complexes were prepared and employed as catalysts for the ROP of e-CL. The catalytic reaction conditions were optimized in detail. The resultant PCL was used to fabricate the PCL/h-MoO3 nanocomposites. The h-MoO3 with three different weight percentages (1, 3 and 5 wt%) was chosen. The structural, functional and morphological properties of nanocomposites were investigated by various spectroscopic and microscopic techniques. The merit of the PCL/h-MoO3 nanocomposites was realized from the improved AC conductivity, dielectric and optical properties compared to the pure PCL.

Highly active metal nanoparticle (MNP) supported cellulose nanofiber (CNF) composites (Au/CNF, Ni/CNF and Ag/CNF) were prepared for the reduction of 4- and 2-nitrophenols (4-NP and 2-NP) in water. Transmission electron microscopy (TEM) images showed that the ultrafine nanoparticles (Au, Ni and Ag NPs) were uniformly deposited on CNFs surface. The content of Au (9.7 wt%), Ni (21.5 wt%) and Ag (22.6 wt%) in Au/CNF, Ni/CNF and Ag/CNF respectively was determined by energy dispersive spectroscopy (EDS) and inductive coupled plasma-mass spectroscopy (ICP-MS) analysis. The chemical state of the MNPs in Au/CNF, Ni/CNF and Ag/CNF was determined by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The significant metal-support interaction was studied by means of XPS. The Au/CNF, Ni/CNF and Ag/CNF demonstrated excellent catalytic activity towards the reduction of nitrophenols to aminophenols in water. To our delight, even a very low amount of catalyst was also found to be good enough to achieve 100% reduction of 4- and 2-NP with a higher reaction rate (within 5 min). The best rate constant (kapp) values were determined for the cellulose nanocomposites. To the best our knowledge, Au/CNF, Ni/CNF and Ag/CNF are the most efficient nanocatalysts for the reduction of 4- and 2-NP reported to date. The catalytic performance of Au/CNF, Ni/CNF and Ag/CNF was compared with previously reported results. A possible mechanism has been proposed for these catalytic systems.

(S)1- N -(1-hydroxy-1,1-diphenyl-3-methylbut-2-yl)-2-hydroxybenzaldimine (DPV) and (S)1- N -(1-hydroxy-3-methylbut-2-yl)-2-hydroxybenzaldimine (LV) were synthesized and investigated as inhibitors for the corrosion of the high carbon steel (HCS) in 1.0 M HCl by electrochemical measurements. According to the electrochemical methods, inhibitor DPV showed higher efficiency in comparison to that of LV. The Tafel polarization method revealed the mixed-mode inhibition of chiral Schiff bases with predominant control of the anodic reaction. The adsorption of the inhibitor molecules onto the HCS surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly supported spontaneous physicochemical adsorption of inhibitor molecules on the HCS surface. The adsorption mechanism for inhibition was supported by Fourier transforms infrared (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy–energy-dispersive X-ray (SEM–EDS) spectroscopic methods, and adsorption isotherms.

The cation sensing property of highly sensitive chromogenic receptor N, N'-bis (salicylidine)-o-phenylene diamine (receptor 1) was studied by visual observation, UV-vis spectroscopy and fluorescence spectroscopy. The proposed study has been targeted to sense the first transition series metal cations like Fe3+, Co2+, Ni2+ and Cu2+. Binding affinity toward Cu2+ is found to be of higher magnitude compared to the other three cations mentioned. Receptor 1 on binding with Fe3+, Co2+ Ni2+ and Cu2+ ions shows fluorescence enhancement which is due to the inhibition of PET mechanism.

The salicylaldimine based colorimetric chemosensors R1 and R2 were synthesized and examined for anion and cation sensing property. The chemosensors R1 and R2 show visual changes towards biologically relevant anions like F− and OH− and also towards various cations such as Fe3+, Co2+, Ni2+, Cu2+ and Sn2+. The sensing action was further confirmed by UV–vis titration and fluorescence spectroscopic studies. The binding constant (Ka) and stoichiometry of host-guest complex formed were determined by Benesi–Hildebrand (B–H) plot and Job's plot method, respectively.

Herein, we report the highly selective binding of Zn2+ ion by the salicylaldimine based Schiff base chromogenic receptor 1 [(N,N′-bis (salicylidine)-o-phenylenediamine]. Receptor 1 senses Zn2+ ion in aqueous medium by colorimetric and fluorescent response in the presence of other metal ions like Pb2+, Hg2+, Sn2+, Cd2+. Receptor 1 on binding with Zn2+ ion exhibits fluorescence enhancement which is due to the inhibition of the (ESIPT) mechanism.