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Direct visualization of soft organic molecules like cellulose is extremely challenging under a high-energy electron beam. Herein, we adopt two ionization damage extenuation strategies to visualize the lattice arrangements of the β-(1→4)-d-glucan chains in carboxylated nanocellulose fibers (C-NCFs) having cellulose II crystalline phase using high-resolution transmission electron microscopy. Direct imaging of individual nanocellulose fibrils with high-resolution and least damage under high-energy electron beam is achieved by employing reduced graphene oxide, a conducting material with high electron transmittance and Ag

The design and development of scalable, efficient photothermal evaporator systems that reduce microplastic pollution are highly desirable. Herein, a sustainable bacterial nanocellulose (BNC)-based self-floating bilayer photothermal foam (PTF

Recent progress in the field of advanced oxidation process (AOP) has triggered the use of surface engineered visible light active TiO2 as a competent photocatalyst material in solar photocatalysis. Herein, we adopted host-guest inclusion complexation for the site-directed immobilization of a model cationic dye, Rhodamine B (RhB) on to the surface of oxygen-rich positively charged TiO2, resulting in rapid mineralization of the dye pollutant under solar irradiation. Relatively recent macrocyclic host, cucurbit[7]uril (CB7) is used as the host for the formation of inclusion complex with RhB. In this study, solar photocatalysis of dye encapsulated system results in 97% mineralization of dye molecules within 10 min with an excellent kinetic rate of 351 × 10−3 min−1. Here, the formation of CB7-RhB inclusion complex enables direct anchoring of encapsulated dye molecules through carboxylic (-COOH) groups of RhB, which in turn facilitate heterogeneous electron transfer resulting in instantaneous and direct cleavage of the chromophore. The binding of CB7 encapsulated RhB to microwave-assisted sonochemically synthesized TiO2 (MST) surface via monodentate ester-like linkage was established by XPS and FT-IR analysis. Gas chromatography (GC) and high-resolution mass spectrometry (HR-MS) substantiate the complete mineralization of RhB and the intactness of CB7 molecular structure after photodegradation, confirming the reusability of CB7/MST as an efficient and economically viable photocatalytic system. Encapsulation of pollutant dye to CB7 host proves to be an excellent approach to facilitate the photoelectron transfer to the photocatalyst and faster mineralization of dye molecules under solar irradiation. Thus, our approach would be a feasible solution for environment-friendly remediation of dye pollutants.

Desalination brine is extremely concentrated saline water; it contains various salts, nutrients, heavy metals, organic contaminants, and microbial contaminants. Conventional disposal of desalination brine has negative impacts on natural and marine ecosystems that increase the levels of toxicity and salinity. These issues demand the development of brine management technologies that can lead to zero liquid discharge. Brine management can be productive by adopting economically feasible methodologies, which enables the recovery of valuable resources like freshwater, minerals, and energy. This review focuses on the recent advances in brine management using various membrane/thermal-based technologies and their applicability in water, mineral, and energy recoveries, considering their pros and cons. This review also exemplifies the hybrid processes for metal recovery and zero liquid discharge that may be adopted, so far, as an appropriate futuristic strategy. The data analyzed and outlook presented in this review could definitely contribute to the development of economically achievable future strategies for sustainable brine management.

Materials that are highly sensitive, easy-to-use, label-free and ultrafast detection of analyte molecules are in great demand. In the present global scenario, there is immense value to be gained from the development of materials that easily detect harmful substances like pesticides or insecticides in fruits and vegetables, environmental pollutants, or other hazardous chemicals. Herein, we demonstrated fluorescent sulphur-doped graphene quantum dots (S-GQDs)-based sensor for the ultrasensitive and selective detection of carbamate pesticides. Green fluorescent S-GQDs with uniform particle size distribution (~5 nm), high crystallinity, monolayer graphene thickness, high quantum yield (27.8%) and high production yield (85%) were synthesised by microwave-assisted sonochemical method using graphene oxide as starting material in five min. KMnO4 is used as oxidising agent and H2SO4 as the precursor for sulphur doping. Sulphur doping is confirmed from XPS and FTIR analysis. Sulphur-doping increases the fluorescence intensity, lifetime and quantum yield of GQDs. This heteroatom doping strategy also results in tuning the optical properties of S-GQD when compared to the undoped system. The green fluorescent S-GQDs in aqueous phase exhibits a detection limit of 0.45 ppb for carbofuran and 1.6 ppb for thiram. Further, S-GQD was incorporated to poly (vinyl alcohol) [PVA] matrix for the preparation of flexible solid-state fluorescent sensing platform. S-GQD imparts fluorescent properties to the polymer film, and thus the film exhibited solid-state fluorescence. PVA/S-GQD flexible film exhibits a LOD of 60 ppb and 210 ppb for carbofuran and thiram, respectively. The selectivity of S-GQD based fluorescent sensor towards carbamate pesticide was investigated. Finally, the developed fluorescent sensor has demonstrated to detect carbofuran in real sample with ppb level sensitivity.

Large scale hotspot engineering is a significant approach for the development of highly efficient surface enhanced Raman scattering (SERS) platforms. Herein, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized nanocellulose fiber (T-NCF) serves as a labyrinth for developing highly sensitive and stable silver-based SERS platform enabling single molecular level SERS detection of analytes. The SERS activity of 4-methylbenzenethiol (4-MBT) in silver nanoconstructs with dissimilar size and shape (denoted as Ag/NCF-I and Ag/NCF-II systems) synthesized by varying T-NCF to Ag+ ratio, exhibited femtomolar sensitivity regardless of their structural variation. A detailed investigation of the SERS performance of both systems with 4-MBT at extremely low concentration (10−15 M) is carried out with the help of large-area Raman intensity mapping in order to evaluate the role of T-NCF in Raman signal enhancement. The analytical enhancement factors (AEFs) for Ag/NCF-I and Ag/NCF-II are calculated to be 1.4 × 1012 and 4.8 × 1011, respectively. A mechanism of local enrichment of analytes is postulated anticipating the ability of flexible nanocellulose fibers to congregate AgNPs, resulting in induced plasmonic coupling of local electromagnetic fields and high-intensity hotspot generation. The potential of T-NCF in generating hotspots can be considered as an alternative strategy to develop standards with long-term colloidal stability and scale-up production of highly sensitive AgNP based plasmonic platforms. This investigation ascertains the potential of nanocellulose fibers in the development of a robust lithography-free SERS sensing platform with single molecule level sensitivity.

An efficient solar active catalyst is in immense demand for water splitting, waste water treatment and environmental remediation applications due to the growing energy crisis. The key to improving the activity of these materials is to increase the surface area, use a dopant and reduce the charge carrier recombination. This growing concern can be addressed by graphitic carbon nitride (g-C3N4) which has excellent visible light activity. In the present work a mesoporous flower like arrangement of carbon nitride–titania nanocomposites obtained through a solvothermal method without the use of any templates at ambient temperature is reported. A detailed investigation on the formation of these mesoflowers has been studied. The properties of the nanocomposite such as efficient absorption in the visible regime and delayed recombination of charge carriers make it an apt material for solar light photocatalysis for the degradation of organic contaminants. The high surface area of 147 m2 g−1 of the mesoflowers has been utilized for heavy metal removal such as Cr(VI) with a sorption percentage of 81% within 2 minutes of contact time in simulated water samples. This report paves the way for a new class of mesoflower nanocomposites for various environmental applications.

The synthesis of shape-tuned silver (Ag) nanostructures with high plasmon characteristics has become of significant importance in in vitro diagnostic applications. Herein, we report a simple aqueous synthetic route using 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized nanocellulose fibers (T-NCFs) and trisodium citrate (TSC) that results in anisotropically grown flower-like Ag nanoconstructs (AgNFs). A detailed investigation of the concentration and sequence of the addition of reactants in the formation of these anisotropic Ag structures is presented. Our experimental results show that the mechanism underlying the formation of AgNFs is facilitated by the synergistic action of T-NCFs and TSC on the directional growth of Ag nuclei during the primary stage, which later develop into a flower-like structure by the ripening of larger particles consuming smaller Ag particles. As a result the final structure comprises flower-like morphology over which several smaller Ag particles (of size10 nm) are adhered. The aqueous AgNF colloid exhibits high stability (ζ = -69.4 mV) and long shelf-life at neutral pH (4 months) by the efficient capping action of T-NCFs. Further, an as-synthesized nanoconstructs shows excellent surface-enhanced Raman scattering activity, which enables ultrasensitive detection of p-aminothiophenol with a concentration down to 10 aM (10

Polyoxometalates (POMs) show great molecular diversity and have significant applications in material science as well as in medicine. In this study, nano-complexation of a novel europium containing polyanion [Cs ⊂ Eu 6 As 6 W 63 O 218 (H 2 O) 14 (OH) 4 ] 25− (EuWAs) with biocompatible chitosan was achieved through ionotropic gelation technique without the aid of any cross-linker. Thus obtained chitosan/EuWAs nano-complex was characterized using DLS and Zeta analysis, FT-IR, SEM, AFM, TG/DTA, EDAX and fluorescence spectroscopy. The cross-linking efficiency of EuWAs with chitosan was calculated to be 81% and the release profile recorded at physiological pH was slow and sustained. Cytotoxicity assays performed on a host of cancer cell lines, viz., KB, MCF-7, PC-3 and A549 proved the anticancer activity of the nanocomplex and flow cytometry studies revealed that reactive oxygen species generation can be the plausible mechanism for the apoptosis induced by this material. Our study has thus indicated the feasibility of using chitosan/EuWAs nano-complex for anticancer applications.

We report a simple method for decorating carboxyl functionalized few-layer graphene with titania (TiO2) nanoparticles by sonication and stirring under room temperature. The nanocomposites showed a remarkable improvement in visible light driven photocatalysis. From Raman and XRD analysis the number of layers of graphene was found to be 3. The TiO2 decorated few-layer graphene (FLG) sheets were characterized by electron microscopy, Raman spectroscopy, infrared spectroscopy, XRD and UV-vis spectroscopy. Titania nanoparticles were uniformly decorated on FLG matrix. The incorporation of titania on FLG enhanced the visible light photocatalytic activity of titania, lowered the electron hole recombination and improved the electron hole mobility. The enhanced life time of the charge carriers was confirmed from the photocurrent measurements. Compared to bare TiO2 nanoparticles the FLG-TiO2 nanocomposites exhibited rapid degradation of Rhodamine B (Rhd B) under solar radiation. It was found that adsorption of dye molecules and the rate of degradation have been greatly enhanced in the FLG decorated with TiO2. The rapid degradation of Rhd B using carboxyl functionalized FLG-TiO2 within 8 min under solar radiation and 20 min under 30 W UV tube with very low concentration (0.01 wt.%) of the photocatalyst is the highlight of the present report. The mechanism of degradation and charge separation ability of the nanocomposite are also explored.

The solid-phase photocatalytic degradation of low density polyethylene (LDPE) with sol–gel synthesized TiO 2 nanoparticles as photocatalyst was investigated under ultraviolet (UV) irradiation in ambient air conditions. TiO 2 nanoparticles were synthesized by optimizing various parameters and the TiO 2 nanoparticles were dispersed in LDPE using cyclohexane solution. This TiO 2 –PE nanocomposite was made in the form of thin films of 40 μm size by facile solution casting method and studied photodegradation of these films. A comparative study on the photodegradation of two different sized TiO 2 incorporated LDPE under UV radiation was carried out. Polyethylene film incorporated with TiO 2 nanoparticles of size 50 nm showed higher degradation rate under UV radiation. Partial oxidation was confirmed from the IR spectrum of the TiO 2 incorporated polyethylene film after radiation exposure. SEM analysis and AFM nanoindentation measurements confirm the degradation. A possible mechanism of TiO 2 assisted degradation of the polyethylene matrix has also been proposed.

An enhancement in the photocatalytic degradation of low-density polyethylene (LDPE) under solar radiation was accomplished by incorporating titania nanoparticles (TiO2) of size 15 nm in the polythene matrix. The LDPE–TiO2 nanocomposite film was prepared through a simple solution casting technique with 0.1 wt% TiO2 nanoparticles. The photocatalytic degradation of the LDPE–TiO2 nanocomposite was investigated using FE-SEM, FT-IR, XPS, XRD, TGA and photoinduced weight loss analysis. To ensure the wide applicability of the method in environmental remediation, the photocatalytic degradation was carried out under solar radiation. We observed that, when exposed to solar radiation, the composite films showed a significant weight loss of 68% within a period of 200 h, which is a remarkable improvement compared to the previous reports. FT-IR and XPS analysis confirmed the presence of carbonyl groups with a carbonyl index of 19, which led to the degradation of LDPE. FE-SEM analysis revealed the mechanism of degradation of the LDPE matrix on the surface of TiO2 through the formation of pores at the interface. Thus we put forward the development of eco-friendly photodegradable plastic as a solution for the growing concerns of plastic pollution.