A simple and straightforward strategy for expedient access to benzoxazoles using chemically engineered 2D magnetic graphene oxide nanosheets as an eco-compatible catalyst

Two-dimensional (2D) graphene oxide nanosheets serve as an excellent support material for immobilizing metal complexes to deal with the drawbacks of homogeneous catalysis. In this work, we report a magnetically retrievable graphene oxide (MGO) based copper nanocatalytic system that has been efficiently exploited for obtaining a series of pharmaceutically and biologically active benzoxazole scaffolds. The nanocatalyst was designed by covalent immobilization of dehydroacetic acid (DHA) onto a magnetic amino-silanized graphene oxide nanosupport which was accompanied by its metallation with copper acetate. The structure of the synthesized MGO hybrid material (Cu@DHA@APTES@MGO) was characterized by numerous physico-chemical techniques such as transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental mapping, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis and energy-dispersive X-ray fluorescence spectroscopy (ED-XRF). The fabricated architectures exhibited high efficiency for cyclization of 2-aminophenols and β-diketones with wide substrate scope, excellent functional group tolerance, a higher conversion percentage (>98%) and a high turnover number (TON). The exceptional catalytic activity could be attributed to the 2D architecture of graphene oxide which provides space for trapping of reactants between 2D graphitic overlayers and metal surfaces and the reaction proceeds to afford benzoxazole products with moderate to excellent conversion percentages. Notably, this nanocomposite could be recovered easily through an external magnetic force and reused for multiple runs without any appreciable loss in its catalytic efficacy.

Synthesis of “(aminomethyl)phosphonic acid-functionalized graphene oxide”, and comparison of its adsorption properties for thorium(IV) ion, with plain graphene oxide

The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and coexisting Na+ ions have no effect on its adsorption. Thanks to Langmuir isotherm, the maximum adsorption capacities of the GO and AMPA-GO were obtained 151.06 and 178.67 mg g−1, respectively. Interestingly, GO and AMPA-GO both showed a higher preference for thorium over uranium so that the average “K d (Th)/K d (U)” for them was 52 and 44, respectively. This data suggests that chromatographic separation of thorium and uranium is feasible by these adsorbents.

Interfacial interaction of graphitic carbon nitride/nanodiamond nanocomposites toward synergistic enhancement of photocatalytic degradation of organic contaminants

Graphitic carbon nitride (g-C₃N₄) has been widely used in various photocatalyst applications. However, compared with conventional metal-based photocatalysts, it exhibits low photocatalytic activity because of the low mobility of its charge carriers. In this study, g-C₃N₄/nanodiamond (ND) nanocomposites were fabricated via a facile single-step heating strategy. Under visible-light irradiation, the optimal g-C₃N₄/ND nanocomposites with 1.0 wt% ND content exhibited an RhB degradation rate more than two times greater than that of the g-C₃N₄. In addition, reutilization experiments showed that the g-C₃N₄/ND nanocomposites exhibit good stability and reusability. This remarkable enhancement of the photocatalytic activity was attributed to the interfacial effect between g-C₃N₄ and ND, which reduces energy-wasteful electron-hole recombination and promotes charge-separation efficiency. Such an approach could accelerate the development of composites for photocatalyst applications and provide more rational guidance and fundamental understanding toward realizing the theoretical limits of interfaces.

Photoluminescent properties of liposome-encapsulated amine-functionalized nanodiamonds

In the present work, amine-functionalized nanodiamonds (NDs) have been encapsulated in liposomes and studied in order to observe the modification of their photoluminescence properties. NDs were functionalized with aromatic amines such as 1-aminopyrene and 2-aminofluorene, and the aliphatic amine 1-octadecylamine. Morphology, structural and optical properties of NDs and amine-modified NDs were analyzed by transmission electron microscopy, atomic force microscopy, scanning electron microscopy, and photoluminescence. The amine-functionalized NDs were successfully encapsulated in lecithin liposomes prepared by the green and conventional methods. The obtained results show significant changes in photoluminescent properties of functionalized NDs, and were more potentialized after liposome encapsulation. Our findings could be applied in the development of new kinds of water-dispersible fluorescent hybrids, liposome-NDs, with the capability of drug encapsulation for use in diagnostics and therapy (theragnostic liposomes). All-optical sensors with possibilities for tailoring their response for other biomedical applications can be also contemplated.

Shellac Thin Films Obtained by Matrix-Assisted Pulsed Laser Evaporation (MAPLE)

We report on the fabrication of shellac thin films on silicon substrates by matrix-assisted pulsed laser evaporation (MAPLE) using methanol as matrix. Very adherent, dense, and smooth films were obtained by MAPLE with optimized deposition parameters, such as laser wavelength and laser fluence. Films with a root mean square (RMS) roughness of 11 nm measured on 40 × 40 µm2 were obtained for a 2000-nm-thick shellac film deposited with 0.6 J/cm2 fluence at a laser wavelength of 266 nm. The MAPLE films were tested in simulated gastric fluid in order to assess their capabilities as an enteric coating. The chemical, morphological, and optical properties of shellac samples were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM).

Covalent functionalization of graphene oxide with d-mannose: evaluating the hemolytic effect and protein corona formation

Graphene oxide mannosylation impacts on RBCs toxicity and plasma protein interactions.

One-step nondestructive functionalization of graphene oxide paper with amines

Direct functionalization of prefabricated free-standing graphene oxide paper (GOP) is the only approach suitable for systematic tuning of its mechanical, thermal and electronic characteristics. However, the traditional liquid-phase functionalization can compromise physical integrity of the paper-like material up to its total disintegration. In the present paper, we attempted to apply an alternative, solvent-free strategy for facile and nondestructive functionalization of GOP with 1-octadecylamine (ODA) and 1,12-diaminododecane (DAD) as representatives of aliphatic amines, and with 1-aminopyrene (AP) and 1,5-diaminonaphthalene (DAN) as examples of aromatic amines. The functionalization can be carried out under moderate heating at 150–180 °C for 2 h in vacuum, and proceeds through both amidation and epoxy ring opening reactions. Comparative characterization of pristine and amine-modified GOP samples was carried out by means of Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopy, thermogravimetric and differential thermal analysis, scanning electron and atomic force microscopy. In addition, we compared stability in water, wettability, electrical conductivity and elastic (Young's) modulus of GOP samples before and after functionalization. The highest content of amine species was obtained in the case of GOP-ODA, followed by GOP-DAD, GOP-AP and GOP-DAN. The functionalization increased mechanical and thermal stability, as well as the electrical conductivity of GOP. The magnitude of each effect depends on the structure of amine employed, which allows for tuning a given GOP characteristic. Morphological characterization showed that, compared to pristine graphene oxide paper, amine-modified mats become relatively ordered layered structures, in which individual GO sheets are organized in a near-parallel fashion.

Solvent-free functionalization of graphene oxide paper with amines is facile, nondestructive, and attractive from economic and environmental points of view.

Graphene oxide and nanodiamond: same carboxylic groups, different complexation properties

DFT calculations explain why carboxylic groups on graphene oxide and nanodiamond have different complexation properties toward Ni(ii) tetraazamacrocyclic cations.

Preparation, characterization and tribological mechanism of nanofluids

This article is focused on various synthetic methods and characterization techniquesof nanofluids. Factors enhancing the stability and lubrication mechanism have been delineated in detail as well.