Highly Active, Selective, and Reusable RuO₂/SWCNT Catalyst for Heck Olefination of Aryl Halides

Very fine RuO₂ nanoparticles (RuO₂NPs) with a mean diameter of about 0.9 nm were decorated on single-walled carbon nanotubes (SWCNTs) by a straightforward “dry synthesis” method. TEM images and the Raman spectrum of the resultant material (RuO₂/SWCNT) revealed excellent adhesion and homogeneous dispersion of the RuO₂NPs on anchoring sites of the SWCNTs. The surface area of RuO₂/SWCNT was found to be 416 m² g^–1. The SEM–EDS results showed that the weight percentage of Ru in RuO₂/SWCNT was 13.8%. The oxidation state of Ru in RuO₂/SWCNT was +4, as confirmed by XPS and XRD analyses. After the complete characterization, a 0.9 mol % loading of RuO₂/SWCNT was used as a nanocatalyst for the Heck olefination of a wide range of aryl halides to yield products in excellent yields with good turnover numbers and turnover frequencies. Less reactive bromo- and chloroarenes were also used for the formation of coupled products in good yields. RuO₂/SWCNT is regioselective, chemoselective, heterogeneous in nature, and reusable. The stability of RuO₂/SWCNT was also studied by means of TEM, ICP-MS, SEM–EDS, and XPS analyses

Human Hair: A Suitable Platform for Catalytic Nanoparticles

Human hair (HH) has been utilized as a support for Au and Ag nanoparticles (NPs) for the very first time. Initially, a very fine human hair powder (HHP) was obtained from HH by a simple ball milling method. The HHP after chemical treatment (e-HHP) was used to prepare two different nanocatalysts, Ag NPs immobilized e-HHP (Ag/HHP) and Au NPs decorated e-HHP (Au/HHP). Influence of e-HHP on the morphology of nanocatalyts and metal–support interactions were studied. Merit of Ag/HHP and Au/HHP was realized from its excellent yields in cyclo addition and <i>aza</i>-Michael reactions, respectively. Reusability and heterogeneity tests of the nanocatalysts were also performed

Industrial-Quality Graphene Oxide Switched Highly Efficient Metal- and Solvent-Free Synthesis of β‑Ketoenamines under Feasible Conditions

Metal- and solvent-free industrial-quality graphene oxide (IQGO)-based highly efficient carbocatalytic system has been developed for the synthesis of β-ketoenamines. Initially, physicochemical properties of IQGO are briefly discussed by means of various microscopic and spectroscopic techniques. The present system accessed a wide range of substrates to yield β-ketoenamines in an excellent yield (86–100%) with 100% selectivity. Catalytic activity of IQGO is compared with other carbon materials such as carbon nanotubes, carbon nanofibers, and graphene nanoplatelets. Cost effective recovery, high level reusability, chemoselective nature, possible scale reaction, and sustainability of IQGO are demonstrated. Based upon experimental results and earlier reports, possible reaction mechanism has been proposed for the synthesis of β-ketoenamines

Sustainable and Versatile CuO/GNS Nanocatalyst for Highly Efficient Base Free Coupling Reactions

A CuO nanoparticles (CuO NPs)/graphene nanosheet (GNS) hybrid was prepared by a very simple method and employed as a nanocatalyst (CuO/GNS) for base free coupling reactions, namely, A³-coupling and <i>aza</i>-Michael reactions. TEM shows that CuO NPs of below ∼35 nm size are homogeneously dispersed on the GNS. Strong adhesion between CuO NPs and GNS was acknowledged by a high Raman <i>I</i>_D/<i>I</i>_G ratio and XPS result. The BET surface area of CuO/GNS was found to be 66.26 m² g^–1. The EDS and XPS investigations revealed that the weight percentage and chemical state of Cu in CuO/GNS were 4.46% and +2, respectively. Under mild reaction conditions, CuO/GNS exhibited an outstanding catalytic activity in terms of yield, turnover number (TON) and turnover frequency (TOF) toward A³-coupling reaction. A small amount of catalyst (10 mg, 0.7 mol % of Cu) is enough to carry out the reactions with a wide range of substrates. The CuO/GNS is stable, heterogeneous in nature and reusable for at least five times without any significant loses of yield. N-oxidation of tertiary amines was also carried out to explore further the activity of CuO/GNS, and the results are found to be excellent. Versatility of the CuO/GNS was realized from the superior catalytic activity of used CuO/GNS in <i>aza</i>-Michael reaction. Finally, GNS (∼95%) and CuO (as CuCl₂) were successfully recovered from the used CuO/GNS and confirmed by TEM, Raman, XPS, XRD and SEM-EDS analyses

Utilization of Human Hair as a Synergistic Support for Ag, Au, Cu, Ni, and Ru Nanoparticles: Application in Catalysis

Human hair powder (HHP) after chemical treatment (e-HHP) has been successfully utilized as a unique catalyst support for immobilization of metal nanoparticles (MNPs). Ag, Au, Cu, Ni, and Ru NPs were used to prepare five different nanocatalysts (MNPs/e-HHP). High-resolution transmission electron microscopy results confirmed the excellent attachment of ultrafine MNPs on the surface of e-HHP. Actual loading of metal in MNPs/e-HHP was determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy analyses. The zero-valent state of MNPs in MNPs/e-HHP and a very strong interaction between MNPs and e-HHP were also proven. The obtained AgNPs/e-HHP, AuNPs/e-HHP, CuNPs/e-HHP, NiNPs/e-HHP, and RuNPs/e-HHP catalysts were employed for the self-coupling of amines, <i>N</i>-oxidation of tertiary amines, <i>aza</i>-Michael reaction, imines synthesis, and oxidation of alcohols, respectively. Reaction conditions were optimized, and the scope of the catalytic systems was extended. The merit of the MNPs/e-HHP materials is shown to be the superior catalytic activity. Advantages, shortcomings, and future scope of the MNPs/e-HHP system are also highlighted

Ag and MoO₃ Nanoparticle-Containing Polyacrylonitrile Nanofiber Membranes for Wound Dressings

Herein, we report the effect of different reducing agents on Ag-MoO3/polyacrylonitrile nanofibers for their promising potential as advanced wound dressings. The nanofibers were treated with NaOH, NaBH4, sodium citrate, and UV light, and their properties were evaluated. Water contact angle measurements revealed that NaOH treatment resulted in a less wettable surface, while NaBH4 and sodium citrate treatments led to more wettable surfaces. UV light treatment induced a slight increase in the surface wettability. Antibacterial inhibition zone tests showed that NaOH and UV treatments exhibited significant inhibitory effects against both Escherichia coli and Bacillus subtilis, while NaBH4 and sodium citrate treatments displayed moderate inhibitory effects. Moreover, silver release profiles demonstrated a sustained release of silver ions over time, with sodium citrate treatment exhibiting a higher release rate. MoO3/polyacrylonitrile displayed a substantially lower stress value, 73% less than that of the blank polyacrylonitrile (PAN) nanofiber. This decrease in the stress value is advantageous for wound dressings, as it allows for improved flexibility and conformability to the wound site. Overall, these findings provide insights into the surface wettability, antimicrobial properties, and silver ion release capabilities of Ag-MoO3/polyacrylonitrile nanofibers under different treatments, highlighting their potential for wound dressing applications