Two-dimensional membranes have gained enormous interest due to their potential to deliver precision filtration of species with performance that can challenge current desalination membrane platforms. Molybdenum disulfide (MoS 2) laminar membranes have recently demonstrated superior stability in aqueous environment to their extensively-studied analogs graphene-based membranes; however, challenges such as low ion rejection for high salinity water, low water flux, and low stability over time delay their potential adoption as a viable technology. Here, we report composite laminate multilayer MoS 2 membranes with stacked heterodimensional one-to two-layer-thick porous nanosheets and nanodisks. These membranes have a multimodal porous network structure with tunable surface charge, pore size, and interlayer spacing. In forward osmosis, our membranes reject more than 99% of salts at high salinities and, in reverse osmosis, small-molecule organic dyes and salts are efficiently filtered. Finally, our membranes stably operate for over a month, implying their potential for use in commercial water purification applications.

No abstract

We report here the synthesis of graphene quantum dots with tunable size, surface chemistry, and fluorescence properties. In the size regime 15-35 nm, these quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon absorption (TPA) cross section (6500 Göppert-Mayer units). Furthermore, through noncovalent tailoring of the chemistry of these quantum dots, we obtain water-stable quantum dots. For example, quantum dots with lysine groups bind strongly to DNA in solution and inhibit polymerase-based DNA strand synthesis. Finally, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, but they do not enter the cell nucleus.

The development of cost-effective cellulose fibers by utilizing agricultural residues have been attracted by the scientific community in the past few years; however, a facile production route along with minimal processing steps and a significant reduction in harsh chemical use is still lacking. Here, we report a straightforward ultrasound-assisted method to extract cellulose nanofiber (CNF) from fibrous waste sugarcane bagasse. X-ray diffraction-based crystallinity calculation showed 25% increase in the crystallinity of the extracted CNF (61.1%) as compared to raw sugarcane bagasse (35.1%), which is coherent with Raman studies. Field emission scanning electron microscopy (FE-SEM) images revealed thread-like CNF structures. Furthermore, we prepared thin films of the CNF using hot press and solution casting method and compared their mechanical properties. Our experiments demonstrated that hot press is a more effective way to produce high strength CNF films; Young’s modulus of the thin films prepared from the hot press was ten times higher than the solution casting method. Our results suggest that a combination of ultrasound-based extraction and hot press-based film preparation is an efficient route of producing high strength CNF films.

In nature, cellulose is a unique lightweight biopolymer with outstanding mechanical and optical properties that is readily available. Rigorous investigations have been conducted to use cellulose as an ingredient in the advanced functional composite design. In this work, a hybrid film composed of homogeneous cellulose nanocrystals (CNC) and high oxidation graphene oxide (GO) is obtained by sufficient blending and vacuum filtration. For the first time through the X‐ray diffraction (XRD) spectrum, the suppression of the originally ordered hydrophobic (200) facet of CNC is observed with increasing concentrations of GO. Further, the originally ordered hydrophilic (110)/(1‐10) facets of CNC remain intact. Through systematic molecular dynamics simulations of a set of simplified CNC–GO sandwich structures, the mechanism behind this hydrophilic/hydrophobic facets manipulation is revealed. The strain induced by the hydrogen bonding between the CNC hydroxyl groups and the oxidation types on GO is the dominant reason to cause the suppression of the hydrophobic facet of CNC in CNC–GO hybrid film. This strain induced mechanism provides an understanding for intrinsically manipulating cellulose–matrix interface and potentially engineering the cellulose based nanocomposite material properties for future advanced materials development.