Nanocelluloses as sustainable membrane materials for separation and filtration technologies: Principles, opportunities, and challenges.

Membrane technology is of great interest in various environmental and industrial applications, where membranes are used to separate different mixtures of gas, solid-gas, liquid-gas, liquid-liquid, or liquid-solid. In this context, nanocellulose (NC) membranes can be produced with predefined properties for specific separation and filtration technologies. This review explains the use of nanocellulose membranes as a direct, effective, and sustainable way to solve environmental and industrial problems. The different types of nanocellulose (i.e., nanoparticles, nanocrystals, nanofibers) and their fabrication methods (i.e., mechanical, physical, chemical, mechanochemical, physicochemical, and biological) are discussed. In particular, the structural properties of nanocellulose membranes (i.e., mechanical strength, interactions with various fluids, biocompatibility, hydrophilicity, and biodegradability) are reviewed in relation to membrane performances. Advanced applications of nanocellulose membranes in reverse osmosis (RO), microfiltration (MF), nanofiltration (NF), and ultrafiltration (UF) are highlighted. The applications of nanocellulose membranes offer significant advantages as a key technology for air purification, gas separation, and water treatment, including suspended or soluble solids removal, desalination, or liquid removal using pervaporation membranes or electrically driven membranes. This review will cover the current state of research, future prospects, and challenges in commercializing nanocellulose membranes with respect to membrane applications.

Double Hook Perylene Diimide as a New Receptor for PAHs: An Experimental and Theoretical Study.

In a one-step reaction, we prepared a dibenzylamine perylene diimide derivative (PDI). Its double hook structure allows for self-association with a constant of Kd ∼108  M-1 determined by fluorescence. We confirmed its ability to bind PAHs using UV/Vis, fluorescence, and 1 H NMR titrations in CHCl3 . The complex formation signature in UV/vis is a new band at 567 nm. The calculated binding constants (Ka ∼104  M-1 ) follow the trend pyrene>perylene>phenanthrene>naphthalene>anthracene. Theoretical modeling of these systems using DFT ωB97X-D/6-311G(d,p) proved helpful in rationalizing the complex formation and the observed association trend. The distinctive signal in UV/vis is due to a charge transfer in the complex from orbitals in the guest to the host. SAPT(DFT) confirmed that the driving forces in the complex formation are exchange and dispersion (π-π interactions). Still, the recognition ability depends on the electrostatic component of the interaction, a minor fraction.

Nanoparticle and Nanostructure Synthesis and Controlled Growth Methods.

Nanomaterials are materials with one or more nanoscale dimensions (internal or external) (i.e., 1 to 100 nm). The nanomaterial shape, size, porosity, surface chemistry, and composition are controlled at the nanoscale, and this offers interesting properties compared with bulk materials. This review describes how nanomaterials are classified, their fabrication, functionalization techniques, and growth-controlled mechanisms. First, the history of nanomaterials is summarized and then the different classification methods, based on their dimensionality (0-3D), composition (carbon, inorganic, organic, and hybrids), origin (natural, incidental, engineered, bioinspired), crystal phase (single phase, multiphase), and dispersion state (dispersed or aggregated), are presented. Then, the synthesis methods are discussed and classified in function of the starting material (bottom-up and top-down), reaction phase (gas, plasma, liquid, and solid), and nature of the dispersing forces (mechanical, physical, chemical, physicochemical, and biological). Finally, the challenges in synthesizing nanomaterials for research and commercial use are highlighted.

Review on Natural, Incidental, Bioinspired, and Engineered Nanomaterials: History, Definitions, Classifications, Synthesis, Properties, Market, Toxicities, Risks, and Regulations.

Nanomaterials are becoming important materials in several fields and industries thanks to their very reduced size and shape-related features. Scientists think that nanoparticles and nanostructured materials originated during the Big Bang process from meteorites leading to the formation of the universe and Earth. Since 1990, the term nanotechnology became very popular due to advances in imaging technologies that paved the way to specific industrial applications. Currently, nanoparticles and nanostructured materials are synthesized on a large scale and are indispensable for many industries. This fact fosters and supports research in biochemistry, biophysics, and biochemical engineering applications. Recently, nanotechnology has been combined with other sciences to fabricate new forms of nanomaterials that could be used, for instance, for diagnostic tools, drug delivery systems, energy generation/storage, environmental remediation as well as agriculture and food processing. In contrast with traditional materials, specific features can be integrated into nanoparticles, nanostructures, and nanosystems by simply modifying their scale, shape, and composition. This article first summarizes the history of nanomaterials and nanotechnology. Followed by the progress that led to improved synthesis processes to produce different nanoparticles and nanostructures characterized by specific features. The content finally presents various origins and sources of nanomaterials, synthesis strategies, their toxicity, risks, regulations, and self-aggregation.

Structural and Optical Properties Correlated with the Morphology of Gold Nanoparticles Embedded in Synthetic Sapphire: A Microscopy Study.

This work reports on the electron microscopy analysis of the structure and morphology of gold nanoparticles produced by ion implantation as well as their relationship to their optical properties. Metalic nanoparticles by ion implantation are usually spherical and formed beneath the surface of a dielectric matrix. In this experiment, the matrix was sapphire. After high-energy Si ion irradiation, the gold nanoparticles were elongated into prolate spheroids. Since the nanoparticles are embedded in a dielectric matrix, secondary electron imaging in a JEOL JSM-7800F at low voltage did not allow their analysis. This work proposes an analysis using backscattered electron imaging in a field emission scanning electron microscopy at higher voltages (20 kV) to explore the morphology of the embedded nanoparticles. The samples were observed by cross-sectional view as well as a top view of the surface of the sapphire matrix for exploration and recognition of their morphology, dimensions, distribution, and composition. The analysis was extended by means of Rutherford backscattering spectrometry, X-ray diffraction, and optical extinction spectroscopy. The nanoparticles exhibited structural and optical properties correlated directly to the morphology observed by microscopy. The beam interaction with the sample and the used parameters was simulated in the CASINO code, from which the depth of exploration with distinct parameters used in microscopy analysis was estimated.

Large area films of alternating graphene-carbon nanotube layers processed in water.

We report the preparation of hybrid paperlike films consisting of alternating layers of graphene (or graphene oxide) and different types of multiwalled carbon nanotubes (N-doped MWNTs, B-doped MWNTs, and pristine MWNTs). We used an efficient self-assembly method in which nanotubes were functionalized with cationic polyelectrolytes in order to make them dispersible in water, and subsequently these suspensions were mixed with graphene oxide (GO) suspensions, and the films were formed by casting/evaporation processes. The electronic properties of these films (as produced and thermally reduced) were characterized, and we found electrical resistivities as low as 3 × 10(-4) Ω cm. Furthermore, we observed that these films could be used as electron field emission sources with extraordinary efficiencies; threshold electric field of ca. 0.55 V/µm, ß factor as high as of 15.19 × 10(3), and operating currents up to 220 µA. These values are significantly enhanced when compared to previous reports in the literature for other carbon nanostructured filmlike materials. We believe these hybrid foils could find other applications as scaffolds for tissue regeneration, thermal and conducting papers, and laminate composites with epoxy resins.