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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.

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 &lt, 99% selectivity towards BH in a very short time. The mechanochemically synthesized NDG-based nanocomposite showed remarkable enhancement in the catalytic performance and increased surface area compared with the catalyst without graphene (i.e., ZnO–MnCO3). 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.

Silver oxide nanoparticles doped manganese (IV) oxide along with varying percentages of highly reduced graphene oxide (HRG) [Ag2O(1%)–MnO2/(X%)HRG] nanocomposites were fabricated through a simple co-precipitation method followed by calcination at 400 °C. The as-prepared nanocomposite upon calcination at 300 °C and 500 °C temperatures, yields the manganese carbonate (MnCO3) and manganese (III) oxide (Mn2O3) composites i.e. Ag2O(1%)–MnCO3/(X%)HRG and Ag2O(1%)–Mn2O3/(X%)HRG, correspondingly. The structural composition of the prepared nanocomposites has confirmed by several characterization techniques. The nanocomposites have successfully utilized as a catalyst for liquid-phase oxidation of aromatic alcohols in presence of O2 as a green oxidant under alkali-free conditions. In addition, a comparative study was performed to assess the activity of the manganese carbonates and manganese oxides for aerial oxidation of benzyl alcohol into benzaldehyde as a model reaction. Effects of various parameters have thoroughly examined in detail and the Ag2O(1%)–MnO2/(5%)HRG catalyst exhibited the highest activity in the aerial oxidation of benzyl alcohol to benzaldehyde with a 100% conversion and >99% selectivity in a remarkably short reaction time (35 min) than the undoped precursor i.e. Ag2O(1%)–MnO2. The presence of HRG dopant greatly enhanced the catalytic performance of Ag2O–MnO2 nanocatalysts could be attributed to the presence of carbon vacancies and topological defects as well as oxygen carrying functionalities on the HRG surface and increase in the surface area. The as-prepared catalyst could be efficiently recycled and reused up to five times without a discernible drop in its catalytic performance and the product selectivity remained unchanged. The prepared catalyst i.e. Ag2O(1%)–MnO2/(5%)HRG was employed as oxidation catalyst for a series of various substituted benzylic and aliphatic alcohols into their respective aldehydes and yielded complete conversion with excellent product selectivity with no further oxidation to acids.

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&ndash, ZrO2) ((X%)NDG/MnCO3&ndash, ZrO2), as the (X%)NDG/MnCO3&ndash, ZrO2 nano-composite was synthesized using physical grinding of separately synthesized NDG and pre-calcined (300 &deg, C) MnCO3&ndash, 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&ndash, ZrO2 exhibits premium specific activity (66.7 mmol&middot, g&minus, 1&middot, h&minus, 1) with 100% conversion of PhCH2OH and &gt, 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&ndash, ZrO2. Under the optimal circumstances, the NDG/MnCO3&ndash, 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&ndash, ZrO2 catalyst were efficiently reused for six subsequent recycling reactions with a marginal decline in performance and selectivity.

A facile and chemical specific method to synthesize highly reduced graphene oxide (HRG) and Pd (HRG@Pd) nanocomposite is presented. The HRG surfaces are tailored with amine groups using 1-aminopyrene (1-AP) as functionalizing molecules. The aromatic rings of 1-AP sit on the basal planes of HRG through π–π interactions, leaving amino groups outwards (similar like self-assembled monolayer on 2D substrates). The amino groups provide the chemically specific binding sites to the Pd nucleation which subsequently grow into nanoparticles. HRG@Pd nanocomposite demonstrated both uniform distribution of Pd nanoparticles on HRG surface as well as excellent physical stability and dispersibility. The surface functionalization was confirmed using, ultraviolet–visible (UV–Vis), Fourier transform infra-red and Raman spectroscopy. The size and distribution of Pd nanoparticles on the HRG and crystallinity were confirmed using high-resolution transmission electron microscopy and powder X-ray diffraction and X-ray photoelectron spectroscopy. The catalytic efficiency of highly reduced graphene oxide-pyrene-palladium nanocomposite (HRG-Py-Pd) is tested towards the Suzuki coupling reactions of various aryl halides. The kinetics of the catalytic reaction (Suzuki coupling) using HRG-Py-Pd nanocomposite was monitored using gas chromatography (GC).

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&ndash, MnO2) decorated graphene oxide (GRO)-based nanocomposites (Ag2O&ndash, MnO2/(X wt.%)GRO), as the Ag2O&ndash, MnO2/(X wt.%)GRO nanocomposite was fabricated by the physical grinding of freshly prepared GRO and pre-annealed (300 &deg, C) mixed metal oxide nanoparticles (NPs) (Ag2O&ndash, 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&ndash, MnO2. The results revealed that (1%)Ag2O&ndash, MnO2/(5 wt.%)GRO catalyst exhibited higher specific performance (13.3 mmol.g&minus, 1.h&minus, 1) with a 100% conversion of benzyl alcohol (BnOH) and &gt, 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&ndash, MnO2/(5 wt.%)GRO) could be efficiently recycled six times with no noticeable loss in its performance and selectivity.

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).

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.

Highly reduced graphene oxide (HRG) nanocomposites of manganese carbonate doped with (1%) zirconia (ZrOx) nanoparticles [ZrOx(1%)–MnCO3/(X%)HRG (where X = 0–7)] were prepared employing a facile co-precipitation method in which the percentage of HRG was varied. The resulting nanocomposite was calcined at 300 °C. Further calcination of the catalyst at 500 °C resulted in the conversion of manganese carbonate to manganese oxide [ZrOx(1%)–Mn2O3/(X%)HRG]. The effect of the inclusion of HRG on the catalytic activity along with its comparative performance between carbonates and their respective oxides was studied for the liquid-phase selective oxidation of benzylic alcohols into corresponding aldehydes using molecular oxygen as the eco-friendly oxidizing agent without adding any external additives or bases. The influence of different parameters such as different percentages of HRG, reaction times, calcination temperatures, catalyst dosages and reaction temperatures have also been systematically studied in order to optimize the catalyst composition and reaction conditions. The inclusion of HRG as a dopant remarkably enhanced the catalytic efficiency of ZrOx–MnCO3 nanocatalysts for the aerobic oxidation of alcohols. The as-prepared catalysts were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). The catalyst with composition ZrOx(1%)–MnCO3/(1%)HRG obtained by calcination at 300 °C exhibited excellent specific activity (60.0 mmol g−1 h−1) with 100% benzyl alcohol conversion and more than 99% product selectivity within an extremely short time (4 min). The same catalyst is employed for the oxidation of a wide range of substituted benzylic and aliphatic alcohols. The catalyst i.e. ZrOx(1%)–MnCO3/(1%)HRG calcined at 300 °C yielded corresponding aldehydes with complete convertibility and selectivity in short reaction times under mild conditions whereas the as-prepared catalyst exhibited high selectivity for aromatic alcohols over aliphatic alcohols. The catalyst was recycled and reused at least five times without any obvious loss in its activity or selectivity.

We report on the synthesis of the zirconia–manganese carbonate ZrO x (x %)–MnCO3 catalyst (where x=1–7) that, upon calcination at 500 °C, is converted to zirconia–manganese oxide ZrO x (x %)–Mn2O3. We also present a comparative study of the catalytic performance of the both catalysts for the oxidation of benzylic alcohol to corresponding aldehydes by using molecular oxygen as the oxidizing agent. ZrO x (x %)–MnCO3 was prepared through co‐precipitation by varying the amounts of Zr(NO3)4 (w/w %) in Mn(NO3)2. The morphology, composition, and crystallinity of the as‐synthesized product and the catalysts prepared upon calcination were studied by using scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, and powder X‐ray diffraction. The surface areas of the catalysts [133.58 m2 g−1 for ZrO x (1 %)–MnCO3 and 17.48 m2 g−1 for ZrO x (1 %)–Mn2O3] were determined by using the Brunauer–Emmett–Teller method, and the thermal stability was assessed by using thermal gravimetric analysis. The catalyst with composition ZrO x (1 %)–MnCO3 pre‐calcined at 300 °C exhibited excellent specific activity (48.00 mmolg−1 h−1) with complete conversion within approximately 5 min and catalyst cyclability up to six times without any significant loss in activity. The specific activity, turnover number and turnover frequency achieved is the highest so far (to the best of our knowledge) compared to the previously reported catalysts used for the oxidation of benzyl alcohol. The catalyst showed selectivity for aromatic alcohols over aliphatic alcohols.

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 PdCl 2 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 PdCl 2 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.

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&ndash, MnCO3/(x%)GRO] and their outcome as an oxidation catalyst for alcohol oxidation under mild conditions using O2 as a clean oxidant. The ZrOx&ndash, 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&ndash, MnCO3, ZrOx&ndash, MnCO3 supported on HRG or ZrOx&ndash, MnCO3/GRO prepared by in-situ growth of ZrOx&ndash, MnCO3 onto GRO followed by calcination. The catalyst with composition (1%)ZrOx&ndash, MnCO3/(1%)GRO exhibited superior specific activity (57.1 mmol/g&middot, h) with complete conversion and &gt, 99% selectivity of the product within a short period of time (7 min) and at a relatively lower temperature (100 &deg, 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.

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.

CoxOy&ndash, manganese carbonate (X%)(CoxOy&ndash, MnCO3 catalysts (X = 1&ndash, 7)) were synthesized via a straightforward co-precipitation strategy followed by calcination at 300 &deg, C. Upon calcination at 500 &deg, C, these were transformed to CoxOy&ndash, dimanganese trioxide i.e., (X%)CoxOy&ndash, Mn2O3. A relative catalytic evaluation was conducted to compare the catalytic efficiency of the two prepared catalysts for aerial oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using O2 molecule as a clean oxidant without utilizing any additives or alkalis. Amongst the different percentages of doping with CoxOy (0&ndash, 7% wt./wt.) on MnCO3 support, the (1%)CoxOy&ndash, MnCO3 catalyst exhibited the highest catalytic activity. The influence of catalyst loading, calcination temperature, reaction time, and temperature and catalyst dosage was thoroughly assessed to find the optimum conditions of oxidation of benzyl alcohol (BzOH) for getting the highest catalytic efficiency. The (1%)CoxOy&ndash, MnCO3 catalyst which calcined at 300 &deg, C displayed the best effectiveness and possessed the largest specific surface area i.e., 108.4 m2/g, which suggested that the calcination process and specific surface area play a vital role in this transformation. A 100% conversion of BzOH along with BzH selectivity &gt, 99% was achieved after just 20 min. Notably, the attained specific activity was found to be considerably larger than the previously-reported cobalt-containing catalysts for this transformation. The scope of this oxidation reaction was expanded to various alcohols containing aromatic, aliphatic, allylic, and heterocyclic alcohols without any further oxidation i.e., carboxylic acid formation. The scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer&ndash, Emmett&ndash, Teller (BET) specific surface area analytical techniques were used to characterize the prepared catalysts. The obtained catalyst could be easily regenerated and reused for six consecutive runs without substantial decline in its efficiency.

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.

Ag2O nanoparticles-doped MnO2 decorated on different percentages of highly reduced graphene oxide (HRG) nanocomposites, i.e., (X%)HRG/MnO2&ndash, (1%)Ag2O (where X = 0&ndash, 7), were fabricated through straight-forward precipitation procedure, and 400 &deg, C calcination, while upon calcination at 300 &deg, C and 500 &deg, C temperatures, it yielded MnCO3 and manganic trioxide (Mn2O3) composites, i.e., [(X%)HRG/MnCO3&ndash, (1%)Ag2O] and [(X%)HRG/Mn2O3&ndash, (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&ndash, (1%)Ag2O showed outstanding specific activity (16.0 mmol/g&middot, h) with complete conversion of 1-phenylethanol and &gt, 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&ndash, (1%)Ag2O catalyst for oxidation of 1-phenylethanol suggested no obvious decrease in its performance and selectivity even after five subsequent runs.

Plant-mediated green synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. In the present study, we synthesized silver nanoparticles (AgNPs) by using an aqueous solution of Saudi Origanum vulgare L. plant extract as a bioreducing agent. The as-synthesized AgNPs were characterized using various microscopic and spectroscopic techniques. The results indicated the formation of crystalline face-centered cubic (fcc) AgNPs. Additionally, FT-IR study confirmed that the O. vulgare L. extract not only functioned as a bioreductant but also stabilized the surface of the AgNPs by acting as a capping agent. Moreover, the effect of the amount of the plant extract on the size and the antimicrobial activity of the NPs was also assessed. It was found that with increasing amounts of plant extract, the size of the NPs was decreased. Moreover, as-synthesized AgNPs as well as O. vulgare L. plant extract were separately tested to examine their antimicrobial activities. The activities were tested against various bacterial and fungal microorganisms including Shigella sonnei, Micrococcus luteus, Escherichia coli, Aspergillus flavus, Alternaria alternate, Paecilomyces variotii, Phialophora alba, and so on. These results evidently show that the inclusion of O. vulgare L. extracts improves the solubility of AgNPs, which led to a significant enhancement in the toxicity of the NPs against the assessed microorganisms.

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.

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 (C 6 H 5 CH 2 OH) to benzaldehyde (C 6 H 5 CHO). 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 ThO 2 -(5%)-NiMnO catalyst calcined at 400 °C exhibited the highest catalytic performance and stability for the selective oxidation of alcohols.

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).

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.

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&ndash, 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 &ldquo, N&rsquo, &rsquo, 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&ndash, visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Brunauer&ndash, Emmett&ndash, Teller (BET). The nanocatalyst displayed outstanding catalytic activity in the Suzuki&ndash, 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).

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.