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Herein, we report the synthesis of ZnO nanoparticles (ZnO-CB NPs) by employing the solution combustion method using an aqueous extract of brinjal calyxes as fuel. Characterization techniques, such as X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), UV–visible spectroscopy, and Scanning electron microscopy (SEM), were used to investigate the structural, optical, and morphological properties of synthesized nanoparticles, respectively. Highly porous hexagonal crystalline ZnO-CB NPs with less than 7 nm particle size were obtained. The photocatalytic performance of synthesized material is measured with Malachite green (MG), Basic brown 1 (BB1), and Acid orange 36 (AO36) as benchmark dyes. It showed that the synthesized material worked effectively under pH 10 with UV light irradiation. The synthesized ZnO-CB NP shows good removal effectiveness of the MG, BB1, and AO36 dyes with 99.3 %, 99.6 %, and 99.5 %, respectively, which can be promising photocatalysts for ecological applications such as wastewater remediation. Further, the synthesized ZnO-CB NP was used as blends in the methyl ester of Millettia pinnata oil (MPME), which is blended 20 % with commercial diesel (MPME20). The synthesized ZnO-CB NP was added to the MPME20 in varying amounts to ascertain its effects on the quality of emissions of various greenhouse gases such as hydrocarbons, COx, and NOx. Moreover, brake thermal efficiency (BTHE) and brake-specific fuel consumption (BSFC) were studied for the blends. The blend MPME20 with 25 mg of ZnO-CB NP, i.e., MPME20-25 mg, ZnO-CB, displays the best performance and reduced emissions.

Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE.

By utilizing the combustion process, nanoparticles can be produced quickly, easily, and in an environmentally friendly manner. In this study, sheep dung is employed as fuel for the synthesis of nickel oxide nanoparticles (NiO-SD), and characterization techniques such as XRD, FTIR, UV, FESEM, and EDX, are used to confirm the as-desired nanoparticles. Malachite green (MG) and methylene blue (MB), respectively, are used as benchmark dyes to measure the photocatalytic effectiveness of the material and systematically investigated the effects of the light source, dye concentration, dose of photocatalyst, and pH value on the effectiveness of photocatalyst and photodegradation kinetics. It is found that the NiO-SD, when exposed to UV light, shows good removal effectiveness of the MB and MG dyes, according to the photodegradation data of 99.9% and 96.8%, respectively. The remarkable photodegradation efficiency of MB and MG dyes over the developed photocatalyst is also explained by a plausible photo-catalytic process. The green-manufactured photocatalyst can be a promising for ecological applications such as waste-water remediation.

The present study demonstrates the synthesis of phase pure hematite (α-Fe2O3) nanoparticles (NPs) using collagen protein and calcium carbonate extracted from eggshell membranes and eggshells, respectively, as organic additives. To test the influence of organic additives on the quality of the resulting NPs, the amount of eggshell powder was varied between 1 to 5 g in aqueous iron nitrate solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and RAMAN analysis confirmed the formation of hematite NPs without any impurities. FTIR spectra revealed the presence of polyphenolic constituents on the surface of the resulting NPs as stabilizers, which may potentially be responsible for the observed antioxidant and antibacterial properties. Furthermore, the stable phase and the presence of low defects divulged the high hardness value (~983 HV) and fracture toughness (8.59 MPa m1/2), which can be exploited for bone implantation. The FE-SEM results demonstrate the formation of spherical particles, which are well-separated NPs. The results of a biodegradation study which was carried out in phosphate-buffered saline (PBS) revealed that the as-prepared NPs retained their hardness even after 72 h of soaking. These prepared NPs showed 95% radical scavenging activity (RSA) and were good carriers against S. aureus bacteria. Moreover, the SEM images of the mineralization of iron oxide NPs confirmed the formation of new bone. After 5 weeks, all pores were filled, and the minerals were deposited on the surfaces of the scaffolds.

Background: Bacterial infections and cancers may cause various acute or chronic diseases, which have become serious global health issues. This requires suitable alternatives involving novel and efficient materials to replace ineffective existing therapies. In this regard, graphene composites are being continuously explored for a variety of purposes, including biomedical applications, due to their remarkable properties.Methods: Herein, we explore, in-vitro, the different biological properties of highly reduced graphene oxide (HRG), including anti-cancer, anti-bacterial, and anti-biofilm properties. Furthermore, to analyze the interactions of graphene with proteins of microbes, in silico docking analysis was also carried out. To do this, HRG was prepared using graphene oxide as a precursor, which was further chemically reduced to obtain the final product. The as-prepared HRG was characterized using different types of microscopic and spectroscopic techniques.Results: The HRG revealed significant cytotoxic ability, using a dose-dependent anti-cell proliferation approach, which substantially killed human breast cancer cells (MCF-7) with IC50 of 29.51 ± 2.68 μg/mL. The HRG demonstrated efficient biological properties, i.e., even at low concentrations, HRG exhibited efficient anti-microbial properties against a variety of microorganisms. Among the different strains, Gram-positive bacteria, such as B. subtilis, MRSA, and S. aureus are more sensitive to HRG compared to Gram-negative bacteria. The bactericidal properties of HRG are almost similar to a commercially available effective antibiotic (ampicillin). To evaluate the efficacy of HRG against bacterial biofilms, Pseudomonas aeruginosa and MRSA were applied, and the results were compared with gentamycin and ampicillin, which are commonly applied standard antibiotics. Notably, HRG demonstrated high inhibition (94.23%) against P.aeruginosa, with lower MIC (50 μg/mL) and IC50 (26.53 μg/mL) values, whereas ampicillin and gentamicin showed similar inhibition (90.45% and 91.31% respectively) but much higher MIC and IC50 values.Conclusion: Therefore, these results reveal the excellent biopotential of HRG in different biomedical applications, including cancer therapy; antimicrobial activity, especially anti-biofilm activity; and other biomedicine-based therapies. Based on the molecular docking results of Binding energy, it is predicted that pelB protein and HRG would form the best stable docking complex, and high hydrogen and hydrophobic interactions between the pelB protein and HRG have been revealed. Therefore, we conclude that HRG could be used as an antibiofilm agent against P. aeruginosa infections.

Semiconducting nanomaterials based heterogeneous photocatalysis represent a low-cost, versatile technique for environmental remediation, including pollution mitigation, energy management and other environmental aspects. Herein, we demonstrate the syntheses of various heterogeneous photocatalysts based on highly reduced graphene oxide (HRG) and vanadium oxide (VOx)-based nanocomposites (HRG–VOx). Different shapes (rod, sheet and urchin forms) of VOx nanoparticles were successfully fabricated on the surface of HRG under solvo-/hydrothermal conditions by varying the amount of water and ethanol. The high concentration of water in the mixture resulted in the formation of rod-shaped VOx nanoparticles, whereas increasing the amount of ethanol led to the production of VOx sheets. The solvothermal condition using pure ethanol as solvent produced VOx nano-urchins on the surface of HRG. The as-prepared hybrid materials were characterized using various spectroscopic and microscopic techniques, including X-ray diffraction, UV–vis, FTIR, SEM and TEM analyses. The photocatalytic activities of different HRG–VOx nanocomposites were investigated for the photodegradation of methylene blue (MB) and methyl orange (MO). The experimental data revealed that all HRG–VOx composite-based photocatalysts demonstrated excellent performance toward the photocatalytic degradation of the organic dyes. Among all photocatalysts studied, the HRG–VOx nanocomposite consisting of urchin-shaped VOx nanoparticles (HRG–VOx-U) demonstrated superior photocatalytic properties towards the degradation of dyes.

The utilization of heterogeneous catalysts during the production of biodiesel potentially minimize the cost of processing due to the exclusion of the separation step. The (X wt%)Ni–ZrO2 (where X = 10, 25 and 50) catalysts prepared through a hydrothermal process were tested for the production of biodiesel by the transesterification of waste cooking oil (WCO) with methanol. The influences of various reaction parameters were systematically optimized. While the physicochemical characteristics of the as-synthesized catalysts were examined using numerous techniques such as FTIR, XRD, TGA BET, EDX, SEM, and HRTEM. Among all the catalysts, (10 wt%)Ni–ZrO2 exhibited high surface area when compared to the pristine ZrO2, (25 wt%)Ni–ZrO2 and (50 wt%)Ni–ZrO2 nanocatalysts. It may have influenced the catalytic properties of (10 wt%)Ni–ZrO2, which exhibited maximum catalytic activity with a biodiesel production yield of 90.5% under optimal conditions. Such as 15:1 methanol to oil molar ratio, 10 wt% catalysts to oil ratio, 8 h reaction time and 180 °C reaction temperature. Furthermore, the recovered catalyst was efficiently reused in several repeated experiments, demonstrating marginal loss in its activity after multiple cycles (five times).

The formation of a C-C bond through Mizoroki-Heck cross-coupling reactions in water with efficient heterogeneous catalysts is a challenging task. In this current study, a highly reduced graphene oxide (HRG) immobilized palladium (Pd) nanoparticle based catalyst (HRG-Py-Pd) is used to catalyze Mizoroki-Heck cross-coupling reactions in water. During the preparation of the catalyst, amino pyrene is used as a smart functionalizing ligand, which offered chemically specific binding sites for the effective and homogeneous nucleation of Pd NPs on the surface of HRG, which significantly enhanced the physical stability and dispersibility of the resulting catalyst in an aqueous medium. Microscopic analysis of the catalyst revealed a uniform distribution of ultrafine Pd NPs on a solid support. The catalytic properties of HRG-Py-Pd are tested towards the Mizoroki-Heck cross-coupling reactions of various aryl halides with acrylic acid in an aqueous medium. Furthermore, the catalytic efficacy of HRG-Py-Pd is also compared with its non-functionalized counterparts such as HRG-Pd and pristine Pd NPs (Pd-NPs). Using the HRG-Py-Pd nanocatalyst, the highest conversion of 99% is achieved in the coupling reaction of 4-bromoanisol and acrylic acid in an aqueous solution in a relatively short period of time (3 h), with less quantity of catalyst (3 mg). Comparatively, pristine Pd NPs delivered lower conversion (∼92%) for the same reaction required a long reaction time and a large amount of catalyst (5.3 mg). Indeed, the conversion of the reaction further decreased to just 40% when 3 mg of Pd-NPs was used which was sufficient to produce 99% conversion in the case of HRG-Py-Pd. On the other hand, HRG-Pd did not deliver any conversion and was ineffective even after using a high amount of catalyst and a longer reaction time. The inability of the HRG-Pd to promote coupling reactions can be attributed to the agglomeration of Pd NPs which reduced the dispersion quality of the catalyst in water. Therefore, the high aqueous stability of HRG-Py-Pd due to smart functionalization can be utilized to perform other organic transformations in water which was otherwise not possible.

Application of nanoparticles in drug delivery has become an emerging phenomenon. This is typically achieved either via custom made nanoparticles or through the functionalization of pre-synthesized nanoparticles with the pharmaceutically active ingredients. In this study, Pregabalin, which is the active pharmaceutical ingredient of commercially available drug Lyrica, is used to functionalize pre-synthesized gold nanoparticles (AuNPs). The work was divided into two parts. The first part determined by synthesis of AuNPs. The second part was achieving conjugation of the AuNPs with Pregabalin to obtain nanocomposites (AuNPs-PGN). AuNPs formed were nanosized, spherical in shape, with a particle size ~35 nm. The probable nanocomposite formation takes place by conjugation between AuNPs and the carboxyl group (COOH) of Pregabalin.

Hydrogel electrolytes for energy storage devices have made great progress, yet they present a major challenge in the assembly of flexible supercapacitors with high ionic conductivity and self-healing properties. Herein, a smart self-healing hydrogel electrolyte based on alginate/poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (alginate/PEDOT:PSS)(A/P:P) was prepared, wherein H2SO4 was employed as a polymeric initiator, as well as a source of ions. PEDOT:PSS is a semi-interpenetrating network (IPN) that has been used in recent studies to exhibit quick self-healing properties with the H₂SO₃ additive, which further improves its mechanical strength and self-healing performance. A moderate amount of PEDOT:PSS in the hydrogel (5 mL) was found to significantly improve the ionic conductivity compared to the pure hydrogel of alginate. Interestingly, the alginate/PEDOT:PSS composite hydrogel exhibited an excellent ability to self-heal and repair its original composition within 10 min of cutting. Furthermore, the graphite conductive substrate-based supercapacitor with the alginate/PEDOT:PSS hydrogel electrolyte provided a high specific capacitance of 356 F g−1 at 100 mV/s g−1. The results demonstrate that the A/P:P ratio with 5 mL PEDOT:PSS had a base sheet resistance of 0.9 Ω/square. This work provides a new strategy for designing flexible self-healing hydrogels for application in smart wearable electronics.

Green syntheses of metallic nanoparticles using plant extracts as effective sources of reductants and stabilizers have attracted decent popularity due to their non-toxicity, environmental friendliness and rapid nature. The current study demonstrates the ecofriendly, facile and inexpensive synthesis of silver nanoparticles (AP-AgNPs) using the extract of aerial parts of the Anthemis pseudocotula Boiss. plant (AP). Herein, the aerial parts extract of AP performed a twin role of a reducing as well as a stabilizing agent. The green synthesized AP-AgNPs were characterized by several techniques such as XRD, UV-Vis, FT-IR, TEM, SEM and EDX. Furthermore, the antimicrobial and antibiofilm activity of as-prepared AP-AgNPs were examined by a standard two-fold microbroth dilution method and tissue culture plate methods, respectively, against several Gram-negative and Gram-positive bacterial strains and fungal species such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and Acinetobacter baumannii (MDR-AB), methicillin-resistant S. aureus (MRSA) and Candida albicans (C. albicans) strains. The antimicrobial activity results clearly indicated that the Gram-negative bacteria MDR-PA was most affected by AgNPs as compared to other Gram-negative and Gram-positive bacteria and fungi C. albicans. Whereas, in the case of antibiofilm activity, it has been found that AgNPs at 0.039 mg/mL, inhibit biofilms formation of Gram-negative bacteria i.e., MDR-PA, E. coli, and MDR-AB by 78.98 ± 1.12, 65.77 ± 1.05 and 66.94 ± 1.35%, respectively. On the other hand, at the same dose (i.e., 0.039 mg/mL), AP-AgNPs inhibits biofilm formation of Gram-positive bacteria i.e., MRSA, S. aureus and fungi C. albicans by 67.81 ± 0.99, 54.61 ± 1.11 and 56.22 ± 1.06%, respectively. The present work indicates the efficiency of green synthesized AP-AgNPs as good antimicrobial and antibiofilm agents against selected bacterial and fungal species.

This work demonstrates hydrazine electro-oxidation and sensing using an ultrathin copper oxide nanosheet (CuO-NS) architecture prepared via a versatile foam-surfactant dual template (FSDT) approach. CuO-NS was synthesised by chemical deposition of the hexagonal surfactant Brij®58 liquid crystal template containing dissolved copper ions using hydrogen foam that was concurrently generated by a sodium borohydride reducing agent. The physical characterisations of the CuO-NS showed the formation of a two-dimensional (2D) ultrathin nanosheet architecture of crystalline CuO with a specific surface area of ~39 m2/g. The electrochemical CuO-NS oxidation and sensing performance for hydrazine oxidation revealed that the CuO nanosheets had a superior oxidation performance compared with bare-CuO, and the reported state-of-the-art catalysts had a high hydrazine sensitivity of 1.47 mA/cm2 mM, a low detection limit of 15 μM (S/N = 3), and a linear concentration range of up to 45 mM. Moreover, CuO-NS shows considerable potential for the practical use of hydrazine detection in tap and bottled water samples with a good recovery achieved. Furthermore, the foam-surfactant dual template (FSDT) one-pot synthesis approach could be used to produce a wide range of nanomaterials with various compositions and nanoarchitectures at ambient conditions for boosting the electrochemical catalytic reactions.

Nanomedicine has been used as a precise treatment for many diseases. The advantage of using nanodrugs is that they have more permeability and less toxicity to cells, which enhances the drug delivery system. Graphene is well known for its potential biological applications in drug, food, and pharma industries. This study aimed to assess the productivity and potentiality of nitrogen-doped graphene (NDG) and to evaluate their anticancer, antimicrobial, and biofilm inhibition activity. Nitrogen-doped graphene was synthesized by using a one-pot facile synthesis of NDG, wherein the NDG was prepared by the reduction of graphene oxide (GO) in the presence of hydrazine hydrate as a reducing agent, while ammonium hydroxide was used as a source of nitrogen on the surface of graphene. As-synthesized NDG was characterized by various characterization techniques such as UV-Vis, FT-IR, XRD, XPS, TEM, and N2 sorption studies analysis. Antimicrobial, anticancer, and biofilm inhibition assays were performed by standard protocols. N-doped graphene (NDG) showed better activity against Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), Bacillus subtillis, Streptococcus pneumoniae, and Streptococcus mutans (p ≤ 0.05), whereas there was no activity against Gram-negative strains in Klebsiella pneumoniae and Pseudomonas aeruginosa. Biofilm inhibition was also improved with NDG compared to the standard ampicillin. NDG showed better results in both MCF-7 and Hela cell lines with IC50 of 27.15 µg/mL and 30.85 µg/mL, respectively. In conclusion, NDG has the best ability for use as a biomolecule, and research studies focusing on proteomics, metabolomics, and in vivo studies are needed to increase the impact of NDG in the drug and pharma industry.

The use of heterogeneous catalyst for biodiesel production can reduce the price of separation process and therefore minimize the biodiesel cost. ZnCuO/N-doped graphene (NDG) catalyst synthesized by facile mechanochemical procedure was tested in the transesterification of waste cooking oil (WCO) with methanol to produce biodiesel. The effects of catalyst loading (0–15 wt%), weight percentage of NDG (10–100%), methanol to oil molar ratio (6:1–18:1), reaction time (2–10 h) and reaction temperature (120–200 °C) were systematically studied at the optimal conditions. Additionally, the properties of the fabricated catalysts were assessed via XRD, FTIR, N2 sorption studies, HRTEM, TGA and Raman spectroscopy. It was found that the ZnCuO/(X%)NDG nanocomposites exhibit enhanced catalytic performance when compared with the ZnCuO catalyst (without NDG) under the identical conditions. The efficacy of the ZnCuO/(X%)NDG nanocomposites has improved owing to the inclusion of NDG in the catalytic system, which in-turn enhanced the properties of the mixed metal oxides (MMO’s) such as surface area, defective sites to a great extent. The ZnCuO/(30%)NDG catalyst displayed a highest catalytic activity towards transesterification of WCO (97.1%) at the optimized conditions of 10 wt% catalyst loading, 15:1 methanol:oil molar ratio, 8 h reaction time and 180 °C reaction temperature. Moreover, the recovered catalyst was successfully reused six cycles with no discernible loss in its activity.

Plant extract-based green synthesis of metal nanoparticles (NPs) has become a popular approach in the field of nanotechnology. In this present investigation, silver nanoparticles were prepared by an efficient and facile approach using Juniperus procera extract as a bioreducing and stabilizing agent. The as-synthesized silver nanoparticles (JP-AgNPs) were characterized by several characterization techniques such as UV–Vis, XRD, FT-IR, HR-TEM, and EDX analysis. The XRD analysis evidently confirms that the as-synthesized Ag nanoparticles (NPs) from Juniperus procera plant extract (JP-AgNPs) are crystalline in nature. FT-IR analysis confirms that the plant extract plays a dual role as a bioreducing and capping agent, while HR-TEM revealed the spherical morphology of as-synthesized JP-AgNPs with the size of ~23 nm. Furthermore, the synthesized JP-AgNPs were evaluated for antibacterial properties against several bacterial and fungal strains such as Staphylococcus aureus (ATCC 12228), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Proteus mirabilis (ATCC 4753), Cryptococcus neoformans (ATCC 16620), and Candida albicans (ATCC 885-653). The JP-AgNPs displayed an efficient mean zone of inhibition (MZI) at 50.00 µL for bacterial associated with fungal pathogens than the plant extract. Mainly, MZI values against microbial pathogens were as follows; E. coli (17.17 ± 0.72 mm), P. mirabilis (14.80 ± 0.17 mm), and C. albicans (14.30 ± 0.60 mm), whereas JP-AgNPs showed moderate activity against P. aeruginosa (11.50 ± 0.29 mm) and C. neoformans (9.83 ± 0.44 mm). Notably, the tested JP-AgNPs have displayed almost similar antimicrobial activities with that of standard antimicrobial drugs, such as streptomycin and nystatin. The enhanced antimicrobial activity of JP-AgNPs can be ascribed to the quality of resultant NPs including, uniform size, shape, and aqueous colloidal stability of nanoparticles.

The present work was carried out to synthesize bismuth ferrite (BFO) nanoparticles by combustion synthesis, and to evaluate the photocatalytic activity of synthesized bismuth ferrite nanoparticles against cefixime trihydrate. BFO nanoparticles were successfully synthesized using bismuth (III) nitrate and iron (III) nitrate by a combustion synthesis method employing different types of fuels such as maltose, succinic acid, cinnamic acid, and lactose. The effects of the different types of fuels on the morphology and size of the bismuth ferrite nanoparticles were investigated. Characterization of the as-obtained bismuth ferrite nanoparticles was carried out by different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), N2-sorption analysis, Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet-visible (UV–vis) spectroscopy. Photoluminescence studies were also carried out for the various bismuth ferrite nanoparticles obtained. Degradation of cefixime trihydrate was investigated under sunlight to evaluate the photocatalytic properties of the bismuth ferrite nanoparticles, and it was found that the bismuth ferrite nanoparticles followed first-order degradation kinetics in solar irradiation in the degradation of antibiotic, cefixime trihydrate.

In this work, ZnO nanocrystals (NCs) have been effectively synthesized by a simple, efficient and cost-effective method using coconut husk extract as a novel fuel. The synthesized NCs are characterized by UV-Vis, XRD, FT-IR, SEM, EDX, Raman and PL studies. The obtained ZnO were found to be UV-active with a bandgap of 2.93 eV. The X-ray diffraction pattern confirms the crystallinity of the ZnO with hexagonally structured ZnO with a crystallite size of 48 nm, while the SEM analysis reveals the hexagonal bipyramid morphology. Photocatalytic activities of the synthesized ZnO NCs are used to degrade methylene blue and metanil yellow dyes.

Nickel–manganese mixed oxides doped with 1, 3, 5 mol% ytterbia have been prepared by co-precipitation method and used in the catalytic oxidation of benzyl alcohol. Catalytic activity of these oxides calcined at 400 °C and 500 °C was studied for selective oxidation of benzyl alcohol to the corresponding aldehyde using molecular oxygen as an oxidizing agent. The results showed that thermally stable 5 mol% ytterbia doped nickel–manganese oxide [Yb2O3-(5%)-Ni6MnO8] exhibited highest catalytic performance when it was calcined at 400 °C. A 100% conversion of the benzyl alcohol was achieved with >99% selectivity to benzaldehyde within a reaction period of 5 h at 100 °C. The mixed oxide prepared has been characterized by scanning election microscopy (SEM) and energy dispersive X-ray analysis (EDXA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and temperature programed reduction (H2-TPR).

The synthesis of 14-aryl 14H-dibenzo[a,j]xanthenes is achieved by a simple condensation reaction between β-naphthol with aryl or alkyl aldehydes in an effective synergetic catalytic system created by combining basic bleaching earth clay and PEG-600. The advantages of the present method include catalyst recyclability, superior product yield, a shorter reaction time and the avoidance of hazardous reagents. Synthesized xanthene derivatives were also screened for their antibacterial activity against Staphylococcus aureus (MTCC 96) and Pseudomonas aeruginosa (Wild).

Catalytic efficacy of metal-based catalysts can be significantly enhanced by doping graphene or its derivatives in the catalytic protocol. In continuation of previous work regarding the catalytic properties of highly-reduced graphene oxide (HRG), graphene-oxide (GO) doped mixed metal oxide-based nanocomposites, herein we report a simple, straightforward and solventless mechanochemical preparation of N-doped graphene (NDG)/mixed metal oxide-based nanocomposites of ZnO–MnCO3 (i.e., ZnO–MnCO3/(X%-NDG)), wherein N-doped graphene (NDG) is employed as a dopant. The nanocomposites were prepared by physical milling of separately fabricated NDG and ZnO–MnCO3 calcined at 300 °C through eco-friendly ball mill procedure. The as-obtained samples were characterized via X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Raman, Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and surface area analysis techniques. To explore the effectiveness of the obtained materials, liquid-phase dehydrogenation of benzyl alcohol (BOH) to benzaldehyde (BH) was chosen as a benchmark reaction using eco-friendly oxidant (O2) without adding any harmful surfactants or additives. During the systematic investigation of reaction, it was revealed that the ZnO–MnCO3/NDG catalyst exhibited very distinct specific-activity (80 mmol/h.g) with a 100% BOH conversion and 3). Under the optimum catalytic conditions, the catalyst successfully transformed various aromatic, heterocyclic, allylic, primary, secondary and aliphatic alcohols to their respective ketones and aldehydes with high selectively and convertibility without over-oxidation to acids. In addition, the ZnO–MnCO3/NDG was also recycled up to six times with no apparent loss in its efficacy.

Due to the recent advancement in the development of various characterization techniques, mixed metal oxide (MMO) based catalysts have gained tremendous attention in the field of catalysis. In this study, we demonstrated the synthesis of a series of novel MMO based catalysts by a facile co-precipitation method. The detailed structure and composition of thoria promoted NiMnO catalysts was investigated using various microscopic and spectroscopic techniques such as, SEM, EDAX, XRD, TGA, BET and TPR. In order to study the effect of the content of thorium oxide on the catalytic activity of the as-prepared material various samples were prepared by the addition of low quantities of thorium oxide with 1%, 3% and 5% on NiMnO. The catalytic performances of the as-prepared catalysts were evaluated towards the aerobic oxidation of benzyl alcohol using molecular oxygen as oxidant. Furthermore, in order to investigate the effect of the calcination temperatures on the catalytic activities of the as-prepared materials, the samples were calcined at three different temperatures at 300 °C, 400 °C and 500 °C. The catalysts displayed significant enhancement in catalytic activity towards the catalytic conversion of benzyl alcohol (C6H5CH2OH) to benzaldehyde (C6H5CHO). Detailed kinetic studies of the reactions using gas chromatography have revealed that the variation of calcination temperature and the percentage of thoria had significant effect on the catalytic performances of the materials. Among all synthesized catalysts ThO2-(5%)-NiMnO catalyst calcined at 400 °C exhibited the highest catalytic performance and stability for the selective oxidation of alcohols.

Green and eco-friendly synthesis of palladium nanoparticles NPs is carried out under facile and eco-friendly conditions using an aqueous solution of Salvadora persica L. (SP) root extract (RE) as a bioreductant, which is commonly known as Miswak. The as-synthesized Pd NPs were characterized using various spectroscopic and microscopic techniques, including, UV–Vis spectroscopy, FT-IR spectroscopy, XRD, ICP-MS and TEM. Detailed investigations of the Pd NPs have confirmed that the polyphenolic phytomolecules present in the RE of Miswak not only act as a bioreductant by facilitating the reduction and growth of Pd NPs, but they also functionalize the surface of Pd NPs and stabilized them in various solvents. Furthermore, the catalytic activity of the green synthesized Pd NPs was also tested toward the Suzuki coupling reactions of various aryl halides in aqueous media. The as-prepared Pd NPs exhibited superior catalytic activity and reusability for the Suzuki coupling reaction in aqueous and aerobic conditions. The kinetics of the reaction studied by GC revealed that the conversion of various aryl halides to biphenyl takes place in a short time.

Due to their excellent physicochemical properties and synergistic effect, graphene metallic NPs based nanocomposites have gained significant attention in various technological fields including catalysis. Here we demonstrate a single pot, facile and environmental friendly synthesis of catalytically active palladium(Pd)@graphene nanocomposites (SP-HRG-Pd) by the simultaneous reduction of graphene oxide (GRO) and PdCl2 using Salvadora persica L. (miswak) root extract (RE) as bioreductant. The synthesis of SP-HRG-Pd was confirmed by various spectroscopic and microscopic techniques, including ultraviolet–visible (UV–vis), Fourier-transform infrared (FT-IR), Raman and X-ray photoelectron (XPS) spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The polyphenolic (flavonoids) and terpenoids rich contents of the miswak RE not only facilitated the reduction of graphene oxide and PdCl2 but also ensured the homogeneous binding of the Pd NPs on graphene, and through stabilization of the surface of SP-HRG-Pd nanocomposites. This also led to the enhanced dispersibility of as synthesized nanocomposites in aqueous solutions. The as-prepared SP-HRG-Pd nanocomposites also demonstrated excellent catalytic activity toward the selective oxidation of aromatic alcohols. Furthermore, in order to study the effect of calcination temperature and concentration of Pd NPs on the catalytic activities of nanocomposites, different samples of SP-HRG-Pd nanocomposites containing different amounts of Pd using various concentrations of Pd precursor were prepared and calcined at various temperatures.

Mixed metal nanoparticles (NPs) have attracted significant attention as catalysts for various organic transformations. In this study, we have demonstrated the preparation of nickel–manganese mixed metal oxide NPs doped with X% nano cerium oxide (X = 1, 3, 5 mol%) by a facile co-precipitation technique using surfactant and surfactant free methodologies. The as-synthesized materials were calcined at different temperatures (300 °C, 400 °C, and 500 °C), and were characterized using various spectroscopic techniques, including, FTIR and XRD. SEM analysis, TEM analysis and TGA were employed to evaluate the structural properties of the as-prepared catalyst. These were evaluated for their catalytic behaviour towards the conversion of benzyl alcohol to benzaldehyde, which was used as a model reaction with molecular oxygen as oxidant. Furthermore, the effect of the variation of the percentage of nano ceria doping and the calcination temperature on the performance of as-prepared mixed metal catalysts was also evaluated. The kinetic studies of the reactions performed employing gas chromatographic technique have revealed that the mixed metal oxide catalyst doped with 5% nano ceria displayed excellent catalytc activity, among various catalysts synthesized.

In recent years, the development of green mechanochemical processes for the synthesis of new catalysts with higher catalytic efficacy and selectivity has received manifest interest. In continuation of our previous study, in which graphene oxide (GRO) and highly reduced graphene oxide (HRG) based nanocomposites were prepared and assessed, herein, we have explored a facile and solvent-less mechanochemical approach for the synthesis of N-doped graphene (NDG)/mixed metal oxide (MnCO3–ZrO2) ((X%)NDG/MnCO3–ZrO2), as the (X%)NDG/MnCO3–ZrO2 nano-composite was synthesized using physical grinding of separately synthesized NDG and pre-calcined (300 °C) MnCO3–ZrO2 via green milling method. The structures of the prepared materials were characterized in detail using X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), Raman, Thermogravimetric analysis (TGA), and N2 adsorption-desorption isotherm analysis. Besides, the obtained nanocomposites were employed as heterogeneous oxidation catalyst for the alcohol oxidation using green oxidant O2 without involving any surfactants or bases. The reaction factors were systematically studied during the oxidation of benzyl alcohol (PhCH2OH) as the model reactant to benzaldehyde (PhCHO). The NDG/MnCO3–ZrO2 exhibits premium specific activity (66.7 mmol·g−1·h−1) with 100% conversion of PhCH2OH and > 99.9% selectivity to PhCHO after only 6 min. The mechanochemically prepared NDG based nanocomposite exhibited notable improvement in the catalytic efficacy as well as the surface area compared to the pristine MnCO3–ZrO2. Under the optimal circumstances, the NDG/MnCO3–ZrO2 catalyst could selectively catalyze the aerobic oxidation of a broad array of alcohols to carbonyls with full convertibility without over-oxidized side products like acids. The NDG/MnCO3–ZrO2 catalyst were efficiently reused for six subsequent recycling reactions with a marginal decline in performance and selectivity.

Plant extract of Pulicaria undulata (L.) was used as both reducing agent and stabilizing ligand for the rapid and green synthesis of gold (Au), silver (Ag), and gold–silver (Au–Ag) bimetallic (phase segregated/alloy) nanoparticles (NPs). These nanoparticles with different morphologies were prepared in two hours by stirring corresponding metal precursors in the aqueous solution of the plant extracts at ambient temperature. To infer the role of concentration of plant extract on the composition and morphology of NPs, we designed two different sets of experiments, namely (i) low concentration (LC) and (ii) high concentration (HC) of plant extract. In the case of using low concentration of the plant extract, irregular shaped Au, Ag, or phase segregated Au–Ag bimetallic NPs were obtained, whereas the use of higher concentrations of the plant extract resulted in the formation of spherical Au, Ag, and Au–Ag alloy NPs. The as-prepared Au, Ag, and Au–Ag bimetallic NPs showed morphology and composition dependent catalytic activity for the reduction of 4-nitrophenol (4-NPh) to 4-aminophenol (4-APh) in the presence of NaBH4. The bimetallic Au–Ag alloy NPs showed the highest catalytic activity compared to all other NPs.

Recently, the development of eco-friendly mechanochemical approaches for the preparation of novel catalysts with enhanced activity and selectivity has gained considerable attention. Herein, we developed a rapid and solvent-less mechanochemical method for the preparation of mixed metal oxide (Ag2O−MnO2) decorated graphene oxide (GRO)-based nanocomposites (Ag2O−MnO2/(X wt.%)GRO), as the Ag2O−MnO2/(X wt.%)GRO nanocomposite was fabricated by the physical grinding of freshly prepared GRO and pre-annealed (300 °C) mixed metal oxide nanoparticles (NPs) (Ag2O−MnO2) using an eco-friendly milling procedure. The as-prepared nanocatalysts were characterized by using various techniques. Furthermore, the nanocomposites were applied as a heterogeneous catalyst for the oxidation of alcohol by employing gaseous O2 as an eco-friendly oxidant under base-free conditions. The mechanochemically obtained GRO-based composite exhibited noticeable enhancement in the surface area and catalytic performance compared to the pristine Ag2O−MnO2. The results revealed that (1%)Ag2O−MnO2/(5 wt.%)GRO catalyst exhibited higher specific performance (13.3 mmol·g−1·h−1) with a 100% conversion of benzyl alcohol (BnOH) and >99% selectivity towards benzaldehyde (BnH) within 30 min. The enhancement of the activity and selectivity of GRO-based nanocatalyst was attributed to the presence of various oxygen-containing functional groups, a large number of defects, and a high specific surface area of GRO. In addition, the as-prepared nanocatalyst also demonstrated excellent catalytic activity towards the conversion of a variety of other alcohols to respective carbonyls under optimal conditions. Besides, the catalyst ((1%)Ag2O−MnO2/(5 wt.%)GRO) could be efficiently recycled six times with no noticeable loss in its performance and selectivity.

High-intensity ultrasonic waves have great potential for the green synthesis of various nanomaterials under mild conditions and offer an excellent alternative for hazardous chemical methods. Herein a facile approach for the eco-friendly synthesis of Au-ZrO2 nanocatalyst with a high catalytic activity using a facile ultrasonic method is presented. Gold (Au) in the nanosize regime was successfully deposited on the surface of solvothermally synthesized monodispersed ZrO2 nanoparticles (ZrO2 NPs) in a very short period of time (5 min) at room temperature. Spherical shape small size Au nanoparticles that are uniformly dispersed on the surface of ZrO2 nanoparticles were obtained. Notably, in the absence of ZrO2 nanoparticles, HAuCl4 could not be reduced, indicating that nano-sized ZrO2 not only acted as support but also helped to reduce the gold precursor at the surface. The as-prepared Au-ZrO2 nanocatalyst was characterized by various techniques. The Au-ZrO2 nanocatalyst served as a highly efficient reducing catalyst for the reduction of 4-nitrophenol. The reaction time decreased with increasing the amount of catalyst.

Zinc oxide nanoparticles doped manganese carbonate catalysts [X% ZnOx–MnCO3] (where X = 0–7) were prepared via a facile and straightforward coprecipitation procedure, which upon different calcination treatments yields different manganese oxides, that is, [X% ZnOx–MnO2] and [X% ZnOx–Mn2O3]. A comparative catalytic study was conducted to evaluate the catalytic efficiency between carbonates and oxides for the selective oxidation of secondary alcohols to corresponding ketones using molecular oxygen as a green oxidizing agent without using any additives or bases. The prepared catalysts were characterized by different techniques such as SEM, EDX, XRD, TEM, TGA, BET, and FTIR spectroscopy. The 1% ZnOx–MnCO3 calcined at 300°C exhibited the best catalytic performance and possessed highest surface area, suggesting that the calcination temperature and surface area play a significant role in the alcohol oxidation. The 1% ZnOx–MnCO3 catalyst exhibited superior catalytic performance and selectivity in the aerial oxidation of 1-phenylethanol, where 100% alcohol conversion and more than 99% product selectivity were obtained in only 5 min with superior specific activity (48 mmol·g−1·h−1) and 390.6 turnover frequency (TOF). The specific activity obtained is the highest so far (to the best of our knowledge) compared to the catalysts already reported in the literatures used for the oxidation of 1-phenylethanol. It was found that ZnOx nanoparticles play an essential role in enhancing the catalytic efficiency for the selective oxidation of alcohols. The scope of the oxidation process is extended to different types of alcohols. A variety of primary, benzylic, aliphatic, allylic, and heteroaromatic alcohols were selectively oxidized into their corresponding carbonyls with 100% convertibility without overoxidation to the carboxylic acids under base-free conditions.

This work reports the zirconia (ZrOx) nanoparticles doped MnCO3 catalysts prepared by facile and simple coprecipitation technique and the synthesis of zirconia-manganese carbonate [X% ZrOx–MnCO3] (where X% = 0–7%) catalyst which upon calcination at 400°C is converted to zirconia-manganese dioxide [1% ZrOx–MnO2] and when calcined at 500°C is converted to zirconia-manganic trioxide [1% ZrOx–Mn2O3]. A comparative catalytic study was performed to investigate the catalytic efficiency between carbonate and oxides for the selective oxidation of 1-phenylethanol by using molecular O2 as a clean oxidant. The influence of several parameters such as w/w% of ZrOx, reaction time, calcination temperature, catalyst amount, and reaction temperature has been thoroughly examined using oxidation of 1-phenylethanol as a model substrate. The 1% ZrOx–MnCO3 precalcined at 300°C exhibited the best catalytic efficiency. It was found that ZrOx nanoparticles also play an essential role in enhancing the effectiveness of the catalytic system for the aerobic oxidation of alcohols. Furthermore, the physical and chemical properties of synthesized catalysts were evaluated by microscopic and spectroscopic techniques. An extremely high specific activity of 40 mmol·g−1·h−1 with a 100% conversion of oxidation product and selectivity of >99% was achieved within extremely short reaction time (6 min).

Graphene and its nanocomposites are showing excellent potential in improving the catalytic performances of different materials. However, the synthetic protocol and its form, such as graphene oxide (GRO) or highly reduced graphene oxide (HRG), influence the catalytic efficiencies. Here, we present, a facile synthesis of graphene oxide (GRO) and ZrOx-MnCO3-based nanocomposites [(1%)ZrOx−MnCO3/(x%)GRO] and their outcome as an oxidation catalyst for alcohol oxidation under mild conditions using O2 as a clean oxidant. The ZrOx−MnCO3/GRO catalyst prepared by incorporating GRO to pre-calcined ZrOx-MnCO3 using ball milling showed remarkable enhancement in the catalytic activities as compared to pristine ZrOx−MnCO3, ZrOx−MnCO3 supported on HRG or ZrOx−MnCO3/GRO prepared by in-situ growth of ZrOx−MnCO3 onto GRO followed by calcination. The catalyst with composition (1%)ZrOx−MnCO3/(1%)GRO exhibited superior specific activity (57.1 mmol/g·h) with complete conversion and >99% selectivity of the product within a short period of time (7 min) and at a relatively lower temperature (100 °C). The catalyst could be recycled at least five times with a negligible decrease in efficiency and selectivity. The catalytic study was extended to different aromatic as well as aliphatic alcohols under optimized conditions, which confirmed the efficiency and selectivity of the catalyst.

Nitrogen-doped graphene (NDG)-palladium (Pd)-based nanocatalysts (NDG@Pd) can be potentially applied as an efficient catalyst for the preparation of biaryls in a Suzuki−Miyaura coupling reaction. Herein, we report the one-pot facile synthesis of an NDG@Pd nanocatalyst, wherein the nanocatalyst was prepared by the simultaneous reduction of graphene oxide (GRO) and PdCl2 in the presence of hydrazine hydrate as a reducing agent, while ammonium hydroxide was used as a source of “N’’ on the surface of graphene. The as-synthesized NDG@Pd nanocatalyst, consisting of smaller-sized, spherical-shaped palladium nanoparticles (Pd-NPs) on the surface of NDG, was characterized by several spectroscopic and microscopic techniques, including high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), ultraviolet−visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Brunauer−Emmett−Teller (BET). The nanocatalyst displayed outstanding catalytic activity in the Suzuki−Miyaura cross-coupling reactions of phenyl halides with phenyl boronic acids under facile conditions in water. The catalytic activity of NDG@Pd was found to be a more efficient catalyst when compared to pristine highly reduced graphene oxide (HRG) based Pd nanocatalyst (HRG@Pd). Furthermore, the reusability of the catalyst was also tested by repeatedly performing the same reaction using the recovered catalyst. The N-doped catalyst displayed excellent reusability even after several reactions.

A single-step solvothermal approach to prepare stabilized cubic zirconia (ZrO2) nanoparticles (NPs) and highly reduced graphene oxide (HRG) and ZrO2 nanocomposite (HRG@ZrO2) using benzyl alcohol as a solvent and stabilizing ligand is presented. The as-prepared ZrO2 NPs and the HRG@ZrO2 nanocomposite were characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD), which confirmed the formation of ultra-small, cubic phase ZrO2 NPs with particle sizes of ~2 nm in both reactions. Slight variation of reaction conditions, including temperature and amount of benzyl alcohol, significantly affected the size of resulting NPs. The presence of benzyl alcohol as a stabilizing agent on the surface of ZrO2 NPs was confirmed using various techniques such as ultraviolet-visible (UV-vis), Fourier-transform infrared (FT-IR), Raman and XPS spectroscopies and thermogravimetric analysis (TGA). Furthermore, a comparative electrochemical study of both as-prepared ZrO2 NPs and the HRG@ZrO2 nanocomposites is reported. The HRG@ZrO2 nanocomposite confirms electronic interactions between ZrO2 and HRG when compared their electrochemical studies with pure ZrO2 and HRG using cyclic voltammetry (CV).

Ag2O nanoparticles-doped MnO2 decorated on different percentages of highly reduced graphene oxide (HRG) nanocomposites, i.e., (X%)HRG/MnO2–(1%)Ag2O (where X = 0–7), were fabricated through straight-forward precipitation procedure, and 400 °C calcination, while upon calcination at 300 °C and 500 °C temperatures, it yielded MnCO3 and manganic trioxide (Mn2O3) composites, i.e., [(X%)HRG/MnCO3–(1%)Ag2O] and [(X%)HRG/Mn2O3–(1%)Ag2O], respectively. These nanocomposites have been found to be efficient and very effective heterogeneous catalysts for selective oxidation of secondary alcohols into their respective ketones using O2 as a sole oxidant without adding surfactants or nitrogenous bases. Moreover, a comparative catalytic study was carried out to investigate the catalytic efficiency of the synthesized nanocomposites for the aerobic oxidation of 1-phenylethanol to acetophenone as a substrate reaction. Effects of several factors were systematically studied. The as-prepared nanocomposites were characterized by TGA, XRD, SEM, EDX, HRTEM, BET, Raman, and FTIR. The catalyst with structure (5%)HRG/MnO2–(1%)Ag2O showed outstanding specific activity (16.0 mmol/g·h) with complete conversion of 1-phenylethanol and >99% acetophenone selectivity within short period (25 min). It is found that the effectiveness of the catalyst has been greatly improved after using graphene support. A broad range of alcohols have selectively transformed to desired products with 100% convertibility and no over-oxidation products have been detected. The recycling test of (5%)HRG/MnO2–(1%)Ag2O catalyst for oxidation of 1-phenylethanol suggested no obvious decrease in its performance and selectivity even after five subsequent runs.

Nanocomposites of highly reduced graphene oxide (HRG) and ZnOx nanoparticles doped manganese carbonate containing different percentages of HRG were prepared via a facile co-precipitation method. The prepared sample calcined at 300 °C yielded i.e., ZnOx(1%)–MnCO3/(X%)HRG (where X = 0–7), calcination at 400 °C and 500 °C, yielded different manganese oxides i.e., ZnOx(1%)–MnO2/(X%)HRG and ZnOx(1%)–Mn2O3/(X%)HRG respectively. The prepared catalyst were subjected to catalytic evaluation and a comparative catalytic study between carbonates and oxides for the liquid-phase aerobic oxidation of benzylic alcohols to corresponding aldehydes using molecular oxygen as an eco-friendly oxidant without adding additives or bases. The influence of various parameters such as percentage of HRG, reaction time, catalyst amount, calcination and reaction temperature was systematically examined to optimize reaction conditions using oxidation of benzyl alcohol as a substrate model. It was found that the catalytic performance is remarkably enhanced after using HRG as catalyst co-dopant for the aerobic oxidation of alcohols, possibly owing to the presence of carbon defects and oxygenated functional groups on HRG surface. The as-synthesized catalysts were characterized by SEM, EDX, XRD, Raman, TGA, BET, and FT-IR. Under optimal conditions, the catalyst with composition ZnOx(1%)–MnCO3/(1%)HRG calcined at 300 °C exhibited remarkable specific activity (57.1 mmol·g−1·h−1) with 100% conversion of benzyl alcohol and more than 99% product selectivity within extremely short time (7 min). The as-prepared catalyst was re-used up to five consecutive times without significant decrease in its activity and selectivity. To the best of our knowledge, the achieved specific activity is the highest so far compared to the earlier reported catalysts used for the benzyl alcohol oxidation. A wide range of substituted benzylic and aliphatic alcohols were selectively oxidized into their corresponding aldehydes with complete convertibility and selectivity in short reaction times without over-oxidation to the acids. Due to their significant low cost, superior reproducibility, excellent catalytic efficiency, the ZnOx(1%)–MnCO3/(X%)HRG nanocomposites possess several application prospect in other organic chemistry reactions.

The synthesis of Palladium (Pd) nanoparticles by green methods has attracted remarkable attention in recent years because of its superiority above chemical approaches, owing to its low cost and ecological compatibility. In this present work, we describe a facile and environmentally friendly synthesis of Pd nanoparticles (Pd NPs) using an aqueous extract of aerial parts of Origanum vulgare L. (OV) as a bioreductant. This plant is available in many parts of the world as well as in Saudi Arabia and is known to be a rich source of phenolic components, a feature we fruitfully utilized in the synthesis of Pd NPs, using various concentrations of plant extracts. Moreover, the OV extract phytomolecules are not only accountable for the reduction and progression of nanoparticles, but they also act as stabilizing agents, which was confirmed by several characterization methods. The as-synthesized Pd nanoparticles (Pd NPs) were analyzed using ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and thermal gravimetric analysis (TGA). Further, FT-IR study has proven that the OV not merely represents a bioreductant but also functionalizes the nanoparticles. Furthermore, the green synthesized metallic Pd NPs were successfully applied as catalysts for selective oxidation of alcohols.

Suzuki-Miyaura coupling reaction catalyzed by the palladium (Pd)-based nanomaterials is one of the most versatile methods for the preparation of biaryls. However, use of organic solvents as reaction medium causes a big threat to environment due to the generation of toxic byproducts as waste during the work up of these reactions. Therefore, the use of water as reaction media has attracted tremendous attention due to its environmental, economic, and safety benefits. In this study, we report on the synthesis of green Pd@graphene nanocatalyst based on an in situ functionalization approach which exhibited excellent catalytic activity towards the Suzuki–Miyaura cross-coupling reactions of phenyl halides with phenyl boronic acids under facile conditions in water. The green and environmentally friendly synthesis of Pd@graphene nanocatalyst (PG-HRG-Pd) is carried out by simultaneous reduction of graphene oxide (GRO) and PdCl2 using Pulicaria glutinosa extract (PGE) as reducing and stabilizing agent. The phytomolecules present in the plant extract (PE) not only facilitated the reduction of PdCl2, but also helped to stabilize the surface of PG-HRG-Pd nanocatalyst, which significantly enhanced the dispersibility of nanocatalyst in water. The identification of PG-HRG-Pd was established by various spectroscopic and microscopic techniques, including, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. The as-prepared PG-HRG-Pd nanocatalyst demonstrated excellent catalytic activity towards the Suzuki-Miyaura cross coupling reactions under aqueous, ligand free, and aerobic conditions. Apart from this the reusability of the catalyst was also evaluated and the catalyst yielded excellent results upon reuse for several times with marginal loss of its catalytic performance. Therefore, the method developed for the green synthesis of PG-HRG-Pd nanocatalyst and the eco-friendly protocol used for the Suzuki coupling offers a mild and effective substitute to the existing protocols and may significantly contribute to the endeavors of green chemistry.

Microbicidal potential of silver nanoparticles (Ag-NPs) can be drastically improved by improving their solubility or wettability in the aqueous medium. In the present study, we report the synthesis of both green and chemical synthesis of Ag-NPs, and evaluate the effect of the dispersion qualities of as-prepared Ag-NPs from both methods on their antimicrobial activities. The green synthesis of Ag-NPs is carried out by using an aqueous solution of readily available Salvadora persica L. root extract (RE) as a bioreductant. The formation of highly crystalline Ag-NPs was established by various analytical and microscopic techniques. The rich phenolic contents of S. persica L. RE (Miswak) not only promoted the reduction and formation of NPs but they also facilitated the stabilization of the Ag-NPs, which was established by Fourier transform infrared spectroscopy (FT-IR) analysis. Furthermore, the influence of the volume of the RE on the size and the dispersion qualities of the NPs was also evaluated. It was revealed that with increasing the volume of RE the size of the NPs was deteriorated, whereas at lower concentrations of RE smaller size and less aggregated NPs were obtained. During this study, the antimicrobial activities of both chemically and green synthesized Ag-NPs, along with the aqueous RE of S. persica L., were evaluated against various microorganisms. It was observed that the green synthesized Ag-NPs exhibit comparable or slightly higher antibacterial activities than the chemically obtained Ag-NPs.

Polyacrylic acid (PAA) is an important industrial chemical, which has been extensively applied in various fields, including for several biomedical purposes. In this study, we report the synthesis and modification of this polymer with various phenol imides, such as succinimide, phthalimide and 1,8-naphthalimide. The as-synthesized derivatives were used to prepare polymer metal composites by the reaction with Zn+2. These composites were characterized by using various techniques, including NMR, FT-IR, TGA, SEM and DSC. The as-prepared PAA-based composites were further evaluated for their anti-microbial properties against various pathogens, which include both Gram-positive and Gram-negative bacteria and different fungal strains. The synthesized composites have displayed considerable biocidal properties, ranging from mild to moderate activities against different strains tested.