A one-step green route to synthesize copper nanocrystals and their applications in catalysis and surface enhanced Raman scattering

Pd nanoparticles decorated on a porous Co(BDC-NH2) MOF as an effective heterogeneous catalyst for dye reduction

Herein, a new catalytic nanocomposite [Co(BDC-NH2)-Pd NPs] composed of a Co(BDC-NH2) MOF has been developed. The catalyst was prepared by modifying the synthesized porous Co(BDC-NH2) MOF with decorated Pd nanoparticles. This nanocatalyst was used as a heterogeneous catalyst in the reductive degradation of organic dyes Rhodamine B and methyl orange with NaBH4. The kinetic and thermodynamic parameters of the reactions were evaluated. The results showed that the low catalyst content could successfully catalyze the dye reduction reaction quickly (1 min). The metal-organic frameworks unique porous morphology of the Co(BDC-NH2) MOF appears to increase dye adsorption and achieve effective dye reduction. Additionally, recyclability studies of the catalyst confirmed that it could be recovered and reused for 10 consecutive reaction cycles with negligible Pd leaching and reduction in catalytic activity.

Occurrence, toxic effects, and mitigation of pesticides as emerging environmental pollutants using robust nanomaterials - A review

Increasing demand of food and agriculture is leading us towards the increasing use and introduction of pesticides to the environment. The upright increase of pesticides in water and associated adverse effects have become a great point of concern to develop proficient methods for their mitigation from water. Various different methods have been traditionally employed for this purpose. Recently, nanotechnology has turned out to be the field of prodigious interest for this purpose, and various specific methods were developed and employed to remove pesticides from water. In this study, nanotechnological methods such as adsorption and degradation have been thoroughly discussed along with their applications and limitations where different types of nanoparticles, nanocomposites, nanotubes, and nanomembranes have played a vital role. However, in this study the most commonly adopted method of adsorption is considered to be the better technique due to its low cost, efficiency, and ease of operation. The adsorption kinetic models were described to explain the efficiency of the nano-adrsorbants in order to evaluate the mass transfer processes. However, various degradation methodologies including photocatalysis and catalytic reduction have also been elaborated. Numerous robust metal, metal oxide and functionalized magnetic nanomaterials have been emphasized, categorized, and compared for the removal of pesticides from water. Additionally, current challenges faced by researchers and future directions have also been provided.

Laser-assisted preparation of Pd nanoparticles on carbon cloth for the degradation of environmental pollutants in aqueous medium

Laser ablation in liquid (LAL), one of the attractive methods for fabrication of nanoparticles, was used for the modification of carbon cloth (CC) by deposition of palladium nanoparticles (Pd NPs); a simple stirring method was deployed to deposit Pd NPs on the CC surface. Characterization techniques viz X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) were applied to study the surface of the ensuing samples which confirmed that LAL technique managed to fabricate and deposit the Pd NPs on the surface of CC. In addition, the catalytic prowess of the carbon cloth-Pd NPs (CC/Pd NPs) was investigated in the NaBH₄- or HCOOH-assisted reduction of assorted environmental pollutants in aqueous medium namely hexavalent chromium [Cr(VI)], 4-nitrophenol (4-NP), congo red (CR) and methylene blue (MB). The CC/Pd NPs system has advantages such as high stability/sustainability, high catalytic performance and easy reusability.

Shape-controlled synthesis of Ni nanocrystals via a wet-chemistry strategy and their shape-dependent catalytic activity

We have synthesized Ni nanocrystals with different shapes via a facile wet-chemistry strategy, and investigated their shape-dependent performances.

Biosynthesis of waste pistachio shell supported silver nanoparticles for the catalytic reduction processes

Silver nanoparticles (NPs) are immobilised on pistachio shell surface by Cichorium intybus L. leaves extract as an antioxidant media. The Fourier transform infrared spectra, X-ray diffraction, field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and transmission electron microscope analyses confirmed the support of silver NPs on the pistachio shell (Ag NPs/pistachio shell). Ag NPs on the pistachio shell had a diameter basically in the 10-15 nm range. Reduction reactions of 4-nitrophenol (4-NP), and organic dyes at ambient condition were used in the investigation of the catalytic performance of the prepared catalyst. Through this research, the Ag NPs/pistachio shell shows a high activity and recyclability, and reusability without loss of its catalytic activity.

Titania-Cellulose Hybrid Monolith for In-Flow Purification of Water under Solar Illumination

In this work, we report a versatile approach for the development of an in-flow purification water system under solar illumination. Cellulose nanofibrils (CNFs) were impregnated with TiO₂ nanoparticles using water as a solvent to obtain hybrid CNF/TiO₂ monoliths with 98% porosity. The opposite surface potential enables an electrostatically induced direct conjugation between TiO₂ and CNFs. Scanning electron microscopy analysis of the surface morphology of the CNF/TiO₂ monolith shows a homogeneous dense coating of titania nanoparticles onto the interconnected nanofibril network, providing a Brunauer-Emmett-Teller surface area of about 80 m²·g^-1 for the hybrid monolith. Furthermore, compression tests reveal a good shape recovery after unloading, thanks to the highly flexible and mechanically stable three-dimensional structure. Finally, the CNF-based hybrids were tested as catalysts for the decomposition of organic pollutants under solar illumination. The tests were performed using a continuous flow reactor with a customized holder, allowing the solution to pass through the monolith. The results reveal a good photocatalytic activity and a long-term stability of the hybrid CNF/TiO₂ monolith toward the decomposition of methyl orange and paracetamol. These features provide a proof of concept for the applicability of the hybrid CNF/TiO₂ monoliths for in-flow purification of water under solar illumination, not only for model dyes but also for organic pollutants of high practical relevance.

Aqueous synthesis of protectant-free copper nanocubes by a disproportionation reaction of Cu2O on synthetic saponite

Here, we report a synthesis of Cu nanocubes by photoreduction of CuSO4. Because synthetic saponite (one of the layered clay minerals) was used as the adsorbent, the nanocubes contained no capping agents or protectants, and the disproportionation reaction of Cu2O with H2SO4 was found to be the key for morphological control.

Biosynthesis of copper nanoparticles using Shewanella loihica PV-4 with antibacterial activity: Novel approach and mechanisms investigation

Metallic nanoparticle based disinfection represents a promising approach for microbial pollution control in drinking water and thus, biosynthesis of non precious metal nanoparticles is of considerable interest. Herein, an original and efficient route for directly microbial synthesis of copper nanoparticles (Cu-NPs) by Shewanella loihica PV-4 is described and their satisfactorily antimicrobial activities are established. Cu-NPs were successfully synthesized and most of them attaching on the bacterial cell surfaces suggested extracellular Cu(II) bioreduction mainly contributed to this biosynthesis. Using a suite of characterization methods, polycrystalline nature and face centered cubic lattice of Cu-NPs were revealed, with size in the range of 10-16 nm. With Cu-NPs dosage of 100 μg/mL and 10⁵ CFU/mL fresh Escherichia coli suspension, the obtained antibacterial efficiency reached as high as 86.3 ± 0.2% within 12 h. Cell damages were primarily caused by the generated reactive oxygen species with H₂O₂ playing significant roles. Both cell membrane and cytoplasm components were destroyed, while the key inactivation mechanisms were lipid peroxidation and DNA damage as concluded through correlation analysis. The cost-effective and eco-friendly biosynthesis of Cu-NPs with high antibacterial activities make them particularly attractive for drinking water disinfection.

From Nano to Micro: using nanotechnology to combat microorganisms and their multidrug resistance

The spread of antibiotic resistance and increasing prevalence of biofilm-associated infections is driving demand for new means to treat bacterial infection. Nanotechnology provides an innovative platform for addressing this challenge, with potential to manage even infections involving multidrug-resistant (MDR) bacteria. The current review summarizes recent progress over the last 2 years in the field of antibacterial nanodrugs, and describes their unique properties, mode of action and activity against MDR bacteria and biofilms. Biocompatibility and commercialization are also discussed. As opposed to the more common division of nanoparticles (NPs) into organic- and inorganic-based materials, this review classifies NPs into two functional categories. The first includes NPs exhibiting intrinsic antibacterial properties and the second is devoted to NPs serving as a cargo for delivering antibacterial agents. Antibacterial nanomaterials used to decorate medical devices and implants are reviewed here as well.

Green synthesis of the Ag/ZnO nanocomposite using Valeriana officinalis L. root extract: application as a reusable catalyst for the reduction of organic dyes in a very short time

A facile and green synthesis of the Ag/ZnO nanocomposite by extract of Valeriana officinalis L. root in the absence of any stabiliser or surfactant has been reported in this work. The green synthesised Ag/ZnO nanocomposite was characterised by Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X‐ray spectroscopy (EDS), elemental mapping, Fourier‐Transform infrared (FT‐IR), X‐ray diffraction analysis (XRD) and UV‐Vis spectroscopy. According to SEM and TEM images, the Ag and ZnO particles are spherical with diameters of less than 20 and 40–50 nm, respectively. The Ag NPs/ZnO nanocomposite proved to be an effective catalyst in the reduction of various dyes including methyl orange (MO), Congo red (CR) and methylene blue (MB) in the presence of NaBH4 in aqueous media at ambient temperature. A maximum degradation (100%) of dyes was performed using Ag/ZnO nanocomposite. The extraordinary performance of the prepared Ag/ZnO nanocomposite is attributed to the synergetic effect induced by both ZnO and Ag NPs in the catalytic degradation of organic dyes. The catalyst could be reused and recovered several times with no significant loss of catalytic activity.

Synthesis, characterization and application of TiO2/Ag recyclable SERS substrates

In this paper, rutile and anatase TiO₂/Ag nanocomposites were prepared by a facile and green photochemical method.

Effect of Gelatin-Stabilized Copper Nanoparticles on Catalytic Reduction of Methylene Blue

The synthesis of copper nanoparticles was carried out with gelatin as a stabilizer by reducing CuSO₄.5H₂O ions using hydrazine. Ascorbic acid and aqueous NaOH were also used as an antioxidant and pH controller, respectively. The effects of NaOH, hydrazine, and concentration of gelatin as stabilizer were studied. The synthesized copper nanoparticles were characterized by UV-vis spectroscopy, XRD, zeta potential measurements, FTIR, EDX, FESEM, and TEM. The formation of CuNPs@Gelatin is initially confirmed by UV-vis spectroscopic analysis with the characteristic band at 583 nm. XRD and TEM reports revealed that CuNPs@Gelatin (0.75 wt.%) is highly crystalline and spherical in shape with optimum average size of 4.21 ± 0.95 nm. FTIR studies indicated the presence of amide group on the surface of the CuNPs indicating the stability of CuNPs which is further supported by zeta potential measurements with the negative optimum value of -37.90 ± 0.6 mV. The CuNPs@G4 showed a good catalytic activity against methylene blue (MB) reduction using NaBH₄ as a reducing agent in an aqueous solution. The best enhanced properties of CuNPs@G4 were found for the 0.75 wt.% gelatin concentration. Thermodynamic parameters (ΔH and ΔS) indicate that under the studied temperature, the reduction of MB by CuNPs@G4 is not feasible and had endothermic in nature.

Fuzzy, copper-based multi-functional composite particles serving simultaneous catalytic and signal-enhancing roles

Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high-performance dual-functional copper-based composite particles that catalyze reactions and simultaneously serve as a SERS (surface enhanced Raman spectra) active, label-free reporting agent. Polyelectrolyte-modified reduced graphene oxide particles are used as the reactive precursors in the fabrication method. Upon adding Cu(NO3)2 solutions into the precursor dispersions, composite particles comprised by copper/copper oxide core and polyelectrolyte-graphene shell were facilely obtained under sonication. The as-prepared composite particles efficiently catalyzed the conversion of 4-nitrophenol to 4-aminophenol and simultaneously acted as the SERS-active substrate to give enhanced Raman spectra of the produced 4-aminophenol. Taking advantage of the assembling capabilities of polyelectrolyte shells, the composite particles could be further assembled onto a planar substrate to catalyze organic reactions, facilitating their application in various conditions. We expect this report to promote the fabrication and application of copper-based multifunctional particles.

Plasmonic fluorescent CdSe/Cu2S hybrid nanocrystals for multichannel imaging and cancer directed photo-thermal therapy

A simple, crude Jatropha curcas (JC) oil-based synthesis approach, devoid of any toxic phosphine and pyrophoric ligands, to produce size and shape tuned CdSe QDs and a further copper sulfide (Cu2S) encasing is presented. The QDs exhibited excellent photoluminescent properties with narrow band gap emission. Furthermore, the Cu2S shell rendered additional cytocompatibility and stability to the hybrid nanomaterial, which are major factors for translational and clinical applications of QDs. The nanocomposites were PEGylated and folate conjugated to augment their cytoamiability and enhance their specificity towards cancer cells. The nanohybrids possess potentials for visible, near infrared (NIR), photoacoustic (PA) and computed tomography (μCT) imaging. The diverse functionality of the composite was derived from the multi-channel imaging abilities and thermal competence on NIR laser irradiation to specifically actuate the photo-thermal ablation of brain cancer cells.

Green synthesis of the Cu/ZnO nanoparticles mediated by Euphorbia prolifera leaf extract and investigation of their catalytic activity

A green synthesis process was developed for the preparation of the Cu/ZnO nanoparticles (NPs) using Euphorbia prolifera leaf extract as a mild, renewable and non-toxic reducing agent and efficient stabilizer without using dangerous, hazardous and toxic materials. The approach of biosynthesis appears to be cost efficient eco-friendly and easy alternative to conventional methods of the Cu/ZnO NPs synthesis. The Cu/ZnO NPs were characterized by FESEM, EDS, elemental mapping, TEM and XRD. TEM micrograph has shown the formation of Cu NPs with the size in the range of 5-17 nm. In addition, the synthesized Cu/ZnO NPs presented excellent catalytic activity for the degradation of Methylene blue (MB) and Congo red (CR) in the presence of NaBH4 in water at room temperature.

Biosynthesis, characterization and catalytic activity of an Ag/zeolite nanocomposite for base- and ligand-free oxidative hydroxylation of phenylboronic acid and reduction of a variety of dyes at room temperature

A green synthesis of an Ag/zeolite nanocomposite and its catalytic activity were investigated. Its catalytic efficiency remains unaltered even after several repeated cycles.

An environmentally friendly route to synthesize Cu micro/nanomaterials with “sustainable oxidation resistance” and promising catalytic performance

Cu micro/nanomaterials with sustainable oxidation resistance and promising catalytic performance.

Nickel Nanoparticle-Decorated Porous Carbons for Highly Active Catalytic Reduction of Organic Dyes and Sensitive Detection of Hg(II) Ions

High surface area carbon porous materials (CPMs) synthesized by the direct template method via self-assembly of polymerized phloroglucinol-formaldehyde resol around a triblock copolymer template were used as supports for nickel nanoparticles (Ni NPs). The Ni/CPM materials fabricated through a microwave-assisted heating procedure have been characterized by various analytical and spectroscopic techniques, such as X-ray diffraction, field emission transmission electron microscopy, vibrating sample magnetometry, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. Results obtained from ultraviolet-visible (UV-vis) spectroscopy demonstrated that the supported Ni/CPM catalysts exhibit superior activity for catalytic reduction of organic dyes, such as methylene blue (MB) and rhodamine B (RhB). Further electrochemical measurements by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) also revealed that the Ni/CPM-modified electrodes showed excellent sensitivity (59.6 μA μM(-1) cm(-2)) and a relatively low detection limit (2.1 nM) toward the detection of Hg(II) ion. The system has also been successfully applied for the detection of mercuric ion in real sea fish samples. The Ni/CPM nanocomposite represents a robust, user-friendly, and highly effective system with prospective practical applications for catalytic reduction of organic dyes as well as trace level detection of heavy metals.

Nitrogen-doped graphene network supported copper nanoparticles encapsulated with graphene shells for surface-enhanced Raman scattering

In this study, we demonstrated nitrogen-doped graphene network supported few-layered graphene shell encapsulated Cu nanoparticles (NPs) (Cu@G-NGNs) as a sensing platform, which were constructed by a simple and scalable in situ chemical vapor deposition (CVD) technique with the assistance of a self-assembled three-dimensional (3D) NaCl template. Compared with pure Cu NPs and graphene decorated Cu NPs, the graphene shells can strengthen the plasmonic coupling between graphene and Cu, thereby contributing to an obvious improvement in the local electromagnetic field that was validated by finite element numerical simulations, while the 3D nitrogen-doped graphene walls with a large surface area facilitated molecule adsorption and the doped nitrogen atoms embedded in the graphene lattice can reduce the surface energy of the system. With these merits, a good surface enhanced Raman spectroscopy (SERS) activity of the 3D Cu@G-NGN painting film on glass was demonstrated using rhodamine 6G and crystal violet as model analytes, exhibiting a satisfactory sensitivity, reproducibility and stability. As far as we know, this is the first report on the in situ synthesis of nitrogen-doped graphene/copper nanocomposites and this facile and low-cost Cu-based strategy tends to be a good supplement to Ag and Au based substrates for SERS applications.

Green synthesis of a natrolite zeolite/palladium nanocomposite and its application as a reusable catalyst for the reduction of organic dyes in a very short time

A natrolite zeolite/palladium (natrolite zeolite/Pd) nanocomposite has been successfully synthesized applying a simple in situ reduction method using an aqueous extract of fruits of Piper longum as a reducing and stabilizing agent.

Synthesis of dendritic iridium nanostructures based on the oriented attachment mechanism and their enhanced CO and ammonia catalytic activities

Branched iridium nanodendrites (Ir NDs) have been synthesized by a simple method based on the oriented attachment mechanism. Transmission electron microscopy images reveal the temporal growth process from small particles to NDs. Precursor concentrations and reaction temperatures have a limited effect on the morphology of Ir NDs. Metal oxide and hydroxide-supported Ir NDs exhibit enhanced activity for catalytic CO oxidation. Particularly, the Fe(OH)x-supported Ir NDs catalyst with a 4 wt% Ir loading show superior CO oxidation catalytic activity with a full conversion of CO at 120 °C. Furthermore, compared with Ir NPs and commercial Ir black, Ir NDs exhibit higher activity and stability for ammonia oxidation. The specific activity and mass activity of Ir NDs for ammonia oxidation are 1.7 and 7 times higher than that of Ir NPs. The improved catalytic activities of Ir NDs are attributed not only to their large specific surface area, but also to their considerably high index facets and rich edge and corner atoms. Hence, the obtained Ir NDs provide a promising alternative for direct ammonia fuel cells and proton-exchange membrane fuel cells.