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Herein for the first time, lignocellulose nanofibrils (LCNF) were prepared from pine-wood powder using microwave (MW)-assisted deep eutectic solvent (DES) pretreatment coupled with high-pressure homogenization. A DES based on choline chloride and lactic acid was employed, and LCNFs prepared by conventional DES pretreatment at 110°C (LCNF-110) and 130°C (LCNF-130) were used for comparison. Although MW treatment offered a high removal of lignin (70%) and hemicellulose (90%) within a short time (110 s), the morphological observations by scanning and transmission electron microscopies revealed excellent defibrillation of the conventionally heat-treated samples. Likewise, LCNF-110 and LCNF-130 exhibited high tensile strengths of 154.6 ± 5.0 and 136.8 ± 1.2 MPa, respectively, whereas that of LCNF-MW was only 75.6 ± 1.4 MPa. Interestingly, LCNF-MW with a lignin content between that of LCNF-110 and LCNF-130 exhibited high thermal stability (Tmax 309.6°C) and potent antioxidant properties. However, the lignin contents of the LCNFs determined their UV-radiation blocking efficiency, where LCNF-110 > LCNF-MW > LCNF-130. Furthermore, all LCNF films exhibited good visible-light transparency, flexibility, and water contact angles (> 87°), indicating their promising potential for packaging applications.

Wet spinning was studied for lignocellulose nanofibrils (TOLCNF) obtained by TEMPO oxidation and mechanical defibrillation of deep eutectic-like solvent-treated lignocellulose. First, the morphological characteristics, water retention value, and specific surface area of the TOLCNF were studied. The effects of the TOLCNF concentration (1.5, 2.0, and 2.5 wt%) and spinning rate (0.1, 1.0, and 10 mL/min) on the wet-spun filament diameter, orientation index, and tensile properties were studied. With an increase in the TOLCNF concentration, the average diameter increased, whereas the orientation index and tensile strength decreased. An increased spinning rate resulted in an increased orientation index and tensile strength but a decrease in the average diameter. To further extend their applicability, Ag nanoparticles (AgNPs) were grown in situ on the filament surface using UV irradiation. Spherical AgNPs with diameters of 30 to 90 nm were observed using scanning electron microscopy. An increased AgNP content improved the tensile strength and elastic modulus of the filaments.

Ionic liquids (ILs) have been widely used for lignocellulose fractionation and lignin isolation. However, the effect of IL treatment on lignin structure has been less explored. This study aimed to explore the chemical structure of lignin isolated by widely used imidazolium based ILs and compare it with the well-known milled wood lignin structure (MWL). Four types of ILs were used, and the effects of the treatment conditions on the isolated lignin (ILL) characteristics were evaluated. As the treatment temperature was increased from 60 to 140 °C, the ILL yield increased, whereas the molecular weight and hydroxyl group content decreased. Among the ILs, [EMIM]Ac produced the highest lignin yield (5.28%), and the ILL obtained had the lowest hydroxyl content (1.27 mM/g) and a molecular weight (Mw) of 29,500 g/mol. Esterification of the ILL isolated with [EMIM]Ac was performed using three fatty acid chlorides, octanoyl chloride (C8), lauroyl chloride (C12), and palmitoyl chloride (C16), to extend its applicability. The effects of esterification on the characteristics of ILL were evaluated, and successful esterification was confirmed using Fourier transform infrared and nuclear magnetic resonance spectroscopies.

Lignin, the most abundant aromatic biopolymer on Earth, has great potential to replace petrochemical-based polymers in the production of value-added products. However, lignin is difficult to extract from lignocellulose because of the recalcitrance of the latter. Herein, the extraction of lignin from lignocellulose using deep eutectic-like solvents (DESs) as green solvents was investigated. Three types of DESs were used, and the effects of treatment temperature (100, 110, and 130 °C) and time (6, 12, and 24 h) on lignin yield and its characteristics were studied. For each DES, the yield of DES-lignin increased with reaction temperature and time. At the same time, the lignin yield obtained using different DESs decreased in the order of choline chloride/lactic acid > betaine/lactic acid > K2CO3/glycerol. At higher temperatures and longer reaction times, lignin with a high molecular weight was produced, which was attributed to the recondensation of lignin fragments. Furthermore, the methoxyl and hydroxyl group contents decreased with increasing reaction temperature and time. Thermal stability studies revealed that the increased molecular weight of DES-lignin enhanced its thermal resistance.

Recently, gold nanoparticles (AuNPs) are extensively used as peroxidase mimics. However, low catalytic activity, high synthesis cost, substrate-induced aggregation in reaction medium and difficulty in recovery and reuse still remain as major challenges. Here, a novel, simple, spontaneous, and reagent-less in-situ method for the production of AuNPs using dialdehyde cellulose nanofibrils (DACNF) is proposed. AuNPs synthesis time and size were greatly influenced by aldehyde content and the optimal aldehyde content for ultra-small AuNPs (≈10 nm) was 2.1 mM/g. AuNPs@DACNFs exhibited broad-spectrum peroxidase activity and steady-state kinetics revealed their better kinetic parameters (low K

Lignocellulose nanofibrils (LCNFs) were produced from the biomass of Mongolian oak for the first time using deep eutectic solvent pretreatment and mechanical defibrillation. Three Choline chloride (CC)-based DESs were selected and the effect of various DES pretreatment conditions on the chemical composition of wood sample was studied first. CC/lactic acid (CC/LA) pretreatment caused high lignin and hemicellulose removal whereas CC/urea (CC/U) and CC/glycerin (CC/GLY) pretreatment increased the fiber’s susceptibility to defibrillation. With the significant influence of temperature, its effect on the subsequent mechanical defibrillation was also studied. For all three DESs, pretreatment condition of 1:2 mol ratio, 6 h time, and 140 °C was found optimal for LCNF preparation. LCNFs with diameter

The use of colloidal nanoparticles suffers from the drawbacks of potential color interference and substrate-induced aggregation. To overcome the limitations, a catalyst was developed by crosslinking Cu-doped carbon dots (Cu-CDs) with chitosan. Cu-CDs with high peroxidase activity were prepared by using a rapid microwave-assisted method. The Cu-CDs containing 6.88% of Cu had an average particle size of 2.25 nm and exhibited 9% of fluorescence quantum yield. The nanozyme/film composite was prepared by crosslinking between the amino groups of Cu-CDs and those of chitosan via a glutaraldehyde linker. A H2O2-mediated tetramethylbenzidine (TMB) oxidation reaction was use to evaluate the peroxidase activity of the film. Based on the TMB color changes, colorimetric assays were developed for the detection of H2O2 and glucose at an absorption wavelength 652 nm. Under the optimal conditions, the linear ranges for H2O2 and glucose were 0.625–40 µM and 1.9–125 µM, respectively, and the detection limits were 0.12 µM and 0.69 µM, respectively. The colorimetric assay was also applied to analyze diluted human serum samples spiked with glucose. Furthermore, this biodegradable, non-toxic, and easy-to-handle nanozyme composite could be stored for over 4 weeks without a significant decrease in activity. Graphical abstract

In the current work, a silver nanoparticles/nitrogen-doped carbon dots (AgNPs/NCDs) nanocomposite was prepared by a microwave-assisted method that does not require additional reducing or stabilizing agents. Multiple analytical techniques were used to characterize the prepared nanocomposite. The nanocomposite exhibited a surface plasmon resonance (SPR) absorption peak at 420 nm, indicating the development of AgNPs with NCDs. Further, HRTEM results confirmed the formation of the nanocomposite with the appearance of lattice fringes of both materials. Additionally, the nanocomposite did not show any precipitation even after two months of storage. The nanocomposite exhibited high catalytic activity towards the reduction of rhodamine B (RhB, 98.83%), methyl red (MR, 97.14%) and 4-nitrophenol (4-NP, 99.95%) at ambient temperature. Besides, the kinetic analysis revealed that the reduction reaction followed pseudo-first-order kinetics and the calculated rate constants (k) for rhodamine B (RhB), methyl red (MR) and 4-nitrophenol (4-NP) were found to be 0.0296 s−1, 0.0233 s−1 and 0.029 s−1, respectively. Moreover, it is a reusable and stable catalyst for reduction reactions up to five cycles without significant loss in catalytic activity. Finally, a plausible mechanism for the reduction of pollutants is also discussed in detail. As a whole, the prepared nanocomposite might display stunning behaviour for wastewater treatment applications.

Effects of deep eutectic solvent (DES) treatment were determined for the chemical composition of the sapwood and heartwood of red pine (Pinus densiflora). Two DES systems were made from the mixture of choline chloride (ChCl) and two different hydrogen bond donors (HBDs), namely, lactic acid (LA) and glycerin (GLY), with different molar ratios (1:2, 1:6, and 1:10). The yield of the solid residue after DES treatment decreased with an increase in the HBD concentration and treatment time, indicating that the water-soluble fraction was increased. The amount of solid residue was lower in the DES with LA than in DES with GLY, and higher in sapwood than in heartwood during both DES treatments. There was no substantial change in the lignin content of the samples, each being 24.7 to 29.5 wt.%, based on the mass of the treated product. Similar to the yield of the solid residue, cellulose and hemicellulose content in the treated product decreased with an increase in the HBD concentration and treatment time, and it was higher in sapwood than in heartwood. The cellulose crystallinity exhibited a slight increase with increasing treatment time, but there was no difference among the treatments using different molar ratios and between sapwood and heartwood.

A novel green approach was developed for producing silver nanoparticles (AgNPs) using lignocellulose nanofibrils (LCNF). This method does not require any additional reducing agent, and the LCNF itself serves both as a reducing agent and a supporting material. A simple autoclave procedure was employed for the synthesis. The synthetic conditions such as concentrations of reactants and reaction time were optimized. Also, the effect of lignin content in LCNF on the formation of AgNPs was evaluated. Three types of cellulose nanofibrils, i.e., HCNF (0% lignin), LCNF-5 (5% lignin), and LCNF-18 (18% lignin), were employed for the preparation of AgNPs. Three types of AgNPs were obtained and thoroughly characterized using UV-vis, Fourier-transform Infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results suggest that LCNF can be employed as a green source for the reduction and effective stabilization of AgNPs, but an increased content of lignin can have an adverse effect on the yield of AgNPs. However, the presence of lignin greatly influenced the particle size. Therefore, LCNF with small amounts of lignin (5%) is best for producing AgNPs.

This study reports the preparation of a polybutylene succinate (PBS) film reinforced with pure cellulose nanofibril (PCNF) and lignocellulose nanofibril (LCNF) by a two-step process that consists of solvent dispersion and twin-screw extrusion. Compared to the conventional one-step process, this method offered improved mechanical properties. The addition of 5% CNF increased the tensile properties up to 18.8%. Further, the effect of the lignin content was also studied by using LCNF as a reinforcement. The LCNF was prepared with and without a deep eutectic solvent (DES) pretreatment to gain LCNF with a lignin content that varied between 5, 19, and 30%. The mechanical properties results show that a 5% addition of LCNF to the PBS matrix increased its tensile strength and elastic modulus. Further, the morphological and thermal properties of the composites were also studied in detail.

In this study, cellulose acetate (CA)/cellulose nanofibril (CNF) film was prepared via solvent casting. CNF was used as reinforcement to increase tensile properties of CA film. CNF ratio was varied into 3, 5, and 10 phr (parts per hundred rubbers). Triacetin (TA) and triethyl citrate (TC) were used as two different eco-friendly plasticizers. Two different types of solvent, which are acetone and N-methyl-2-pyrrolidone (NMP), were also used. CA/CNF film was prepared by mixing CA and CNF in acetone or NMP with 10% concentration and stirred for 24 h. Then, the solution was cast in a polytetrafluoroethylene (PTFE) dish followed by solvent evaporation for 12 h at room temperature for acetone and 24 h at 80 °C in an oven dryer for NMP. The effect of solvent type, plasticizers type, and CNF amount on film properties was studied. Good dispersion in NMP was evident from the morphological study of fractured surface and visible light transmittance. The results showed that CNF has a better dispersion in NMP which leads to a significant increase in tensile strength and elastic modulus up to 38% and 65%, respectively, compared with those of neat CA. CNF addition up to 5 phr loading increased the mechanical properties of the film composites.

Although photocatalytic degradation is an ideal strategy for cleaning environmental pollution, it remains challenging to construct a highly efficient photocatalytic system by steering the charge flow in a precise manner. In this work, a novel, highly efficient, stable, and visible light active hybrid photocatalytic system consisting of FeWO4 and g-C3N4 nanosheets (CNNs) has been successfully prepared by an in situ self-assembly solvothermal approach. Several characterization techniques were employed to study the phase structures, morphologies, optical properties, surface composition and chemical state of the as-prepared samples. SEM and TEM results demonstrated that the FeWO4 nanoparticles are uniformly dispersed on the surface of CNNs with a diameter of about 10–20 nm, which could provide maximum interfacial contact and a synergistic coupling effect between FeWO4 and CNNs. XPS and FTIR results confirmed that there was strong electrostatic interaction between FeWO4 and CNNs, suggesting the formation of heterojunctions between them. In addition, UV-DRS and PL spectroscopy revealed that the FeWO4/CNN composites exhibited increased visible light absorption and improved charge generation/separation efficiency. As a result, the photocatalytic activity of the FeWO4/CNNs was enhanced in comparison with pure FeWO4 and CNNs for rhodamine B (RhB) and tetracycline (TC) degradation under natural sunlight irradiation. The photocatalytic efficiency of the optimal FeWO4/CNN composite (10 wt% FeWO4/CNNs) for the degradation of RhB (TC) was about 13.26 (4.95) and 86.2 (31.1) times higher than that of pure FeWO4 and CNNs, respectively. Meanwhile, the 10 wt% FeWO4/CNN sample exhibits good photocatalytic stability in recycling experiments. The enhanced photocatalytic activity may be attributed to the formation of the Z-scheme system between FeWO4 and CNNs, effectively prolonging the lifetime of the photoexcited electrons generated by CNNs and the photoexcited holes generated by FeWO4, which was subsequently confirmed by the active species trapping experiments and the calculation of relative band alignments. This work opens up a new feasible avenue to synthesize visible light active Z-scheme photocatalysts for application in energy production and environmental remediation.

Nanozyme-based dye degradation methods are promising for the remediation of water pollution. Though Pd nanoparticles (PdNPs) are known to act as nanozymes, their dye degradation capability has not been investigated. Low nanozyme activities, easy aggregation, difficulties in recovery and reuse are the major challenges in achieving this. For the first time, cellulose nanofibrils-supported PdNPs (PdNPs/PCNF) as a novel nanozyme with good peroxidase and oxidase-mimicking activities and easy recyclability is explored for dye degradation. An efficient and rapid method of PdNPs/PCNF preparation was demonstrated by adjusting the pH and microwave irradiation. Enzyme kinetic studies revealed good kinetic parameters and specific activities of 415 and 277 U/g for peroxidase and oxidase, respectively. PdNPs/PCNF offered 99.64% degradation of methylene blue within 12 min (0.468 min

In this study, the effect of lignin esterification with fatty acid chloride on the properties of lignin and lignin/poly(lactic acid) (PLA) composites was investigated. Lignocellulose (Pinus densiflora S. et Z.) was treated using a deep eutectic solvent (DES) with choline chloride (ChCl)/lactic acid (LA). From the DES-soluble fraction, DES-lignin (DL) was isolated by a regeneration process. Lignin esterification was conducted with palmitoyl chloride (PC). As the PC loading increased for DL esterification, the Mw of esterified DL (EDL) was increased, and the glass transition temperature (Tg) was decreased. In DL or EDL/PLA composite films, it was observed that EDL/PLA had cleaner and smoother morphological characteristics than DL/PLA. The addition of DL or EDL in a PLA matrix resulted in a deterioration of tensile properties as compared with neat PLA. The EDL/PLA composite film had a higher tensile strength and elastic modulus than the DL/PLA composite film. DL esterification decreased water absorption with lower water diffusion coefficients. The effect of lignin esterification on improving the compatibility of lignin and PLA was demonstrated. These results are expected to contribute to the development of high-strength lignin composites.

Effectual degradation of toxic water contaminants is a crucial step in water purification and designing an efficient semiconductor based hybrid structure photocatalyst is a good approach to achieve this. Benefiting from the combination of semiconductors, a series of novel visible-light active flower-like MoS

Nanocellulose materials have attained rapid development in recent days, owing to its widespread availability, renewability, environmental friendly nature, less weight and nanoscale dimension, exceptional mechanical properties, low density, cost-effective, biocompatibility, and biodegradability. The above groundbreaking properties of nanocellulose offer as a promising cheap alternative to replacing fossil resources polymers. Recently, more attention has been focused on the isolation of cellulose from various sustainable sources. Two different types of nanocellulose, that is cellulose nanocrystals (CNC) and nanofibrils (CNF), have diverse morphology and characteristics. Rod-like structure of CNC might be isolated from natural sources such as agricultural and industrial wastes, plants, tunicates, and bacterial cellulose using acid hydrolysis of the amorphous region. Similar isolation from same sources was accounted for web-like network CNF with the help of various mechanical processes such as grinding, high-pressure homogenization, and purification. In this book chapter, we have manifested in details about the isolation of nanocellulose from various sources such as wood and nonwood followed by characterization of nanocellulose with different techniques and its wide range of applications.

The present work is emphasized on converting toxic cigarette butts (CBs) into highly fluorescent N,S-codoped carbon dots by a facile hydrothermal approach and exploring their multiple applications. The as-produced carbon dots (CBCDs) exhibited bright and stable fluorescence with a quantum yield of 26% and used as a label-free probe for “on–off–on” sequential detection of Fe3+ and ascorbic acid (AA). The fluorescence of CBCDs can be significantly quenched by Fe3+ ions through static quenching and restored upon the subsequent addition of AA due to the reduction of Fe3+ to Fe2+ by AA. This nanoprobe presented great selectivity and excellent sensitivity to Fe3+ and AA with a detection limit of 0.13 and 0.2 μM, respectively. Furthermore, the nanoprobe was extended to biosystem (intracellular detection) and successfully applied for the detection of Fe3+ in real water (tap, bore, and pond) and AA in biological samples (human urine and serum). In addition, we have constructed an IMPLICATION logic gate based on these unique sensing characteristics. The “visible–invisible” and “UV–visible” property explored their use as invisible ink for security applications. Furthermore, highly photostable fluorescent polymer films were prepared by incorporating CBCDs in poly(vinyl alcohol). It is anticipated that the strong and stable fluorescence emission nature of these films might find direct or indirect applications in various optical/optoelectronic devices, ranging from fluorescent displays to light-emitting diodes.

Here we demonstrate a rapid green synthetic approach for the production of gold nanoparticles (AuNPs) using microwave irradiation, in which Annona squamosa L (AS) fruit waste extract served as a sole agent for both reduction and stabilization. Synthetic conditions were optimized by monitoring the changes surface plasmon resonance (SPR) peak, zeta potential and DLS size distribution. TEM results revealed that under optimized synthetic conditions monodispersed and spherical nanoparticles with average diameter of 5 ± 2 nm could be achieved. The possible mechanism involved in the formation of AuNPs was interpreted by FTIR. The formed AuNPs dispersion remained stable to environmental conditions like temperature, ionic strength and pH of the medium and exhibited high shelf life. Further they exhibited admirable catalytic activity for the efficient reduction of Congo red & Methylene Blue and 4-Nitrophenol in the presence of NaBH4, which is stable even after five cycles of reaction.

Lignocellulose nanofibrils (LCNFs) with different lignin contents were prepared using choline chloride (ChCl)/lactic acid (LA), deep eutectic solvent (DES) pretreatment, and subsequent mechanical defibrillation. The LCNFs had a diameter of 15.3–18.2 nm, which was similar to the diameter of commercial pure cellulose nanofibrils (PCNFs). The LCNFs and PCNFs were wet-spun in CaCl2 solution for filament fabrication. The addition of sodium alginate (AL) significantly improved the wet-spinnability of the LCNFs. As the AL content increased, the average diameter of the composite filaments increased, and the orientation index decreased. The increase in AL content improved the wet-spinnability of CNFs but deteriorated the tensile properties. The increase in the spinning rate resulted in an increase in the orientation index, which improved the tensile strength and elastic modulus.

Here, for the first time we have developed a novel green synthesis method where chitosan acts as a reducing agent and as a colloidal stabilizer, together with polyquaternium for the synthesis of platinum nanoparticles (PtNPs). It was observed that only chitosan stabilized PtNPs (Ch@PtNPs) were stable upto pH 5, with a diameter of around 89 nm. The diameter of the Ch@PtNPs increased with the increase in pH, indicating the unstability of Ch@PtNPs at neutral and alkaline medium. However, when polyquaternium (PQ) (a cationic polymer) was added as a stabilizer along with to chitosan, the diameter of chitosan/polyquaternium stabilized PtNPs (Ch/PQ@PtNPs), i.e. 87 nm, remained almost constant up to pH 9. Similarly, the pH-dependent decrease in the surface charge of Ch@PtNPs was also attenuated with the addition of polyquaternium. This indicates high colloidal stability of Ch/PQ@PtNPs in acidic, neutral, as well as alkaline mediums. It was observed that Ch/PQ@PtNPs exhibited high antibacterial activity against Staphylococcus aureus, as compared to uncapped PtNPs and Ch@PtNPs. Thus, the addition of PQ increases the antibacterial properties of Ch/PQ@PtNPs against Staphylococcus aureus by enhancing the stability of PtNPs at neutral pH.

Herein, we developed a gold nanoparticles (AuNPs) based label free colorimetric probe for the sensitive and selective detection of Copper (II) ions (Cu2+). Fabrication of the detection system involves a single step in which plant derived, nontoxic polysaccharide carboxymethyl gum karaya (CMGK) acts as reducing, stabilizing and functionalizing agent. Synthetic conditions were optimized by using UV–Vis spectra, zeta potential and DLS analysis and as synthesized AuNPs were thoroughly characterized by TEM, FTIR, and XRD analysis. They exhibited excellent stability to conditions like pH, salt and have a longer shelf life. These CMGK capped AuNPs exhibited a selective colorimetric response to Cu2+ ions with a visible colour change from red to blue, which could be due to the Cu2+ induced aggregation and the same was confirmed by TEM and DLS analysis. The detection conditions such as pH, amount of nanoparticles used and incubation time were optimized. Under the optimal detection conditions, the present system exhibited a good linear correlation (R2 = 0.998) in the range of 10–1000 nM of copper with a limit of detection 10 nM. Further the method was successfully applied for the detection of copper in real water samples and biological samples (human plasma and urine).

In this work, novel ternary composites were prepared by depositing both carbon dots (CDs) and Ag nanoparticles (AgNPs) onto the surface of g-C 3 N 4 nanosheets (CNNs). The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) techniques. The characterization results demonstrated that the CDs and AgNPs were well distributed on the surface of CNNs. The photocatalytic activities of all the samples were evaluated by degrading methyl orange (MO) and p-nitrophenol (PNP) in aqueous media under sunlight irradiation. Among the prepared samples, CNNs decorated with 2 wt% CDs and 1 wt% AgNPs showed higher degradation performance. The enhanced performance was attributed to the improved light harvesting capability and effective charge carrier separation at the AgNPs/CDs/CNNs interface. Superoxide radical species and photogenerated holes were found to be predominant reactive species responsible for the photodegradation of these pollutants. A suitable mechanism was proposed and discussed in detail.

An environmental benign in-situ formation and growth of gold nanoparticles (AuNPs) on TEMPO-oxidized cellulose nanofibrils (TOCNF) is reported here. With the active functional groups (aldehyde and carboxyl), TOCNF served as a synchronized reducing and supporting agent for the formation of AuNPs. The entire synthesis process was completed within 30 s under microwave irradiation and regarded as ultra-fast. As obtained AuNPs@TOCNF nanohybrid suspension was freeze-dried to form strong water-activated shape recovery 3D foam. Internal morphology and porosity of the foam were studied by SEM and BET. AuNPs@TOCNF foams exhibited excellent catalytic activity for the discoloration of cationic and anionic dyes in batch and dynamic column processes. The spent foams can be easily recovered and reused up to five cycles with more than 98 % efficiency. During the catalytic processes, no obvious deterioration of the foam structure was observed. Practical applicability of the nanocatalyst was evaluated by treating spiked sea water sample.

Fe-doped carbon dots (FeCDs) with high peroxidase (POD)-like activity were prepared by a rapid microwave-assisted method and immobilized on cellulose nanofibrils (CNF) to produce a composite nanopaper. The POD activity of the nanopaper was evaluated by the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and applied to the colorimetric detections of hydrogen peroxide (H2O2) and glucose. CNF acted as a support for the nanozyme, thus imparting it with reusability. It also adsorbed the chromogen during the reaction to induce a color change, thus acting as a test strip for portable on-site detection. A smartphone was employed to monitor this color change which made the whole detection process simple and economical. Under optimal conditions, this method afforded linear ranges of 6–42 μM and 10–70 μM and detection limits of 0.93 and 1.73 μM for the H2O2 and glucose, respectively. The results of the quantification of glucose in human serum samples were comparable to those of the standard glucose oxidase (GOD)–POD method. Further, the nanopaper was potentially reused for ten cycles and presented over a month of shelf life.

Novel microwave-assisted green in-situ synthesis of positively charged gold nanoparticles (AuNPs) supported by cationic cellulose nanofibrils (C.CNF) within 30 s and devoid of additional reducing agent is reported. Peroxidase activity of these positive AuNPs was studied and that appeared to be superior over its negative charged counterpart. Further the AuNPs@C.CNF is casted into a film which makes it reusable. Using TMB substrate, simple and sensitive colorimetric detection methods for H2O2 and glucose were established. Under optimal conditions, the linear ranges were found to be 0.5-30 μM and 1-60 μM, and the detection limits were 0.30 and 0.67 μM for H2O2 and glucose, respectively. The film was potentially reused for the detection of glucose up to five cycles without a decrease in the activity. Further, this technique was employed to quantify glucose in human serum samples, and the obtained results were comparable with those of the standard GOD-POD method.

Here, we report a novel, facile and green approach for the synthesis of highly fluorescent carbon dots (CDs) with 28% quantum yield by utilizing onion waste as a precursor and by employing a simple autoclave. Optical and physicochemical properties of as synthesized CDs were studied using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), X-ray diffraction (XRD), Raman, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), UV-visible, fluorescence spectroscopy and elemental analysis. These CDs exhibited high aqueous dispersibility, excitation dependent fluorescence emission and excellent stability to various effects like pH, high ionic strength and continuous irradiation. It was observed that the presence of Fe3+ ions could result in a strong fluorescence quenching, hence these CDs were applied as a fluorescent probe for the selective & sensitive detection of Fe3+ ions and a good linear correlation (R2 = 0.996) in the range of 0–20 μM with a detection limit of 0.31 μM was obtained. Cytotoxicity studies performed on both normal (HEK-293 cells) and cancerous (HeLa) cells revealed their excellent biocompatibility and they were further employed as fluorescent probes for multicoloured (blue, green and red) imaging of HeLa cells. Impressed by their high selectivity, photo stability and excellent biocompatibility, the Fe3+ detection capability of these CDs was further evaluated in HeLa cells and applied for real water samples.

A one step thermal carbonization method for the preparation of solid state emitting N-doped carbon dots (NCDs) powder with hydrophobic nature is reported here. This method directly offers glowing NCDs powder in large quantities and do not involve tedious purification and drying steps. Physicochemical properties of as produced NCDs were explored using various analytical techniques and optical properties were studied in different solvents. The NCDs powder was applied for the rapid visualization of latent fingerprints (LFPs) on various porous and non-porous surfaces. With their green emission, NCDs were able to provide sufficient contrast on auto-fluorescent surfaces also. The LFPs developed with NCDs powder clearly presented level 2 and level 3 ridge details which are sufficient for the individual identification.

The present study describes a microwave-assisted synthesis of well-dispersed palladium nanoparticles (PdNPs). For the first time,Frankincense resin (FR) obtained from the tree of Boswellia sacra is explored for the preparation of PdNPs. This method is rapid, inexpensive and devoid of toxic chemicals. FR aqueous extract with reducing polysaccharides and other phytochemicals served as an effective reducing and stabilizing agent for PdNPs. Formation of PdNPs was preliminarily confirmed by UV–visible and mechanism of formation was proposed from Fourier transform infrared spectroscopy. Transmission electron microscopic images displayed spherical PdNPs with an average size of 11 ± 2 nm. Catalytic activity studies revealed that the PdNPs act as an efficient catalyst for the reduction of both cationic (Methylene Blue) and anionic (Congo red) dye pollutants. Moreover, the PdNPs can be recovered and reused for five cycles without a significant loss in their catalytic activity.

The adsorption characteristics of silver nanoparticles (AgNPs) on cellulose nanofibrils (CNFs) were investigated herein with different chemical compositions. Pure cellulose nanofibers (PCNFs), lignocellulose nanofibers (LCNFs) with different lignin contents (LCNF-20% and LCNF-31%), and holocellulose nanofibers (HCNFs) with hemicellulose were used in this study. Furthermore, CNFs and silver nitrate were mixed and reacted at different temperatures, and NaBH4 was used as the reducing agent. First, the effect of temperature on the adsorption of AgNPs on PCNF was studied. At an optimal temperature (45 &deg, C), the effect of the chemical composition of CNF was studied. The overall properties were analyzed using UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The AgNPs were found to be spherical under all conditions with average diameter of 5.3 nm (PCNF), 5.6 nm (HCNF), 6.3 nm (LCNF-20%) and 6.6 nm (LCNF-31%). The amount of AgNPs adsorbed on the CNF was observed to vary, based on the chemical composition of the CNF. The adsorption amount of AgNPs was observed to increase in the order of LCNF-20% &gt, PCNF &gt, LCNF-31% &gt, HCNF. The results indicated that phenolic hydroxyl groups present in LCNF significantly affected the adsorption of AgNPs.

Although photocatalytic degradation is an ideal strategy for cleaning environmental pollution, it remains challenging to construct a highly efficient photocatalytic system by steering the charge flow in a precise manner. In this work, a novel, highly efficient, stable, and visible light active hybrid photocatalytic system consisting of FeWO

Sunlight-driven C–TiO2/FeTiO3 composites were synthesized with different weight fractions of FeTiO3. The as-prepared samples were characterized by UV–Visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence. Under sunlight irradiation, the C–TiO2/FeTiO3 photocatalysts degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure FeTiO3 or carbon-doped titanium dioxide (C–TiO2), and the C–TiO2/FeTiO3 photocatalyst with 10 wt% of FeTiO3 exhibited the highest photocatalytic activity. The enhancement of photocatalytic activity was mainly ascribed to the formation of a heterojunction between C–TiO2 and FeTiO3, which facilitated the transfer and separation of photogenerated electron–hole pairs. The quenching effects of different scavengers demonstrated that the reactive superoxide radicals (·O2 −) and hydroxyl radicals (·OH) played a major role in the MO degradation. The possible photocatalytic mechanism is discussed on the basis of the band structures of C–TiO2 and FeTiO3. To further enhance the photocatalytic efficiency, double-heterojunctioned CQD/C–TiO2/FeTiO3 composite was prepared by loading carbon quantum dots onto the C–TiO2/FeTiO3 surface.

Here, we developed a simple green approach for the synthesis of highly fluorescent nitrogen doped carbon dots (NCDs) using Lantana camara berries. Optical and physicochemical properties of as synthesized NCDs were extensively studied by using various analytical techniques. NCDs exhibited bright fluorescence with Quantum yield as high as 33.15%, which is stable to various effects like heat, pH, ionic strength and continuous irradiation. Furthermore, the NCDs presented highly selective and sensitive fluorescence response towards Pb2+ which explored their potential to serve as a label-free fluorescent probe for the effective detection of Pb2+. As developed NCDs based probe exhibited a great linear response (R2=0.998) towards Pb2+ in the concentration range of 0-200nM with a detection limit of 9.64nM. The probe further presented high precision without any interference and was successfully applied for the detection of Pb2+ in the real water and human sera (serum and urine) samples. Cytotoxicity studies on both cancerous (human breast adenocarcinoma MCF-7) and normal (Human embryonic kidney HEK-293) cell lines revealed their excellent biocompatibility. With their low cytotoxicity, strong fluorescence and excitation-dependent emission, NCDs were successfully applied as multi-colour bioimaging agents and Pb2+ detection capabilities were further evaluated in live cells.

Background Herein, we report a green, microwave irradiated synthesis of gold nanoparticles by using a simple, low cost and ecofriendly technique. The green technique has been developed for the synthesis of gold nanoparticles (AuNPs) from HAuCl4 using papaya leaf extract. The papaya leaf extract served both as a reductant and a stabilizer. Method The synthesized AuNPs had been characterized by UV-Visible spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential and Transmission electron microscopy (TEM) techniques. Results The results indicated that the synthesized nanoparticles were crystalline, stable, well dispersed and spherical in shape and had an average diameter of 15 ± 2 nm. The AuNPs showed excellent catalytic activity for the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) in the presence of NaBH4. The effects of concentration of NaBH4, catalyst dose and temperature on the formation of nanoparticles were studied. The activation energy was found to be 28.15 ± 1.14 kJ/mol. Conclusions The papaya leaf extract capped AuNPs are highly stable, and have showed effective catalytic activity in the reduction of 4-NP to 4-AP and antimicrobial activity on both gram-positive and gram-negative bacteria.

Photocatalytic materials for environmental remediation of organic pollutants and heavy metals require not only a strong visible light response and high photocatalytic performance, but also the regeneration and reuse of catalysts. In this work, 1D/2D V2O5 nanorods/g-C3N4 nanosheets (VONRs/CNNs) composites were prepared by a facile impregnation method and employed in the degradation of a Congo red (CR) and reduction of Cr (VI) under sunlight irradiation. The as-prepared samples were studied by several characterization techniques including XRD, SEM, TEM, EDS, XPS, FTIR, UV–vis DRS and PL. Results revealed that the interface interaction between VONRs and CNNs was recognized via V2O5 nanorods loading on the surface of g-C3N4 nanosheets, improving the separation and transfer of photogenerated electron-hole pairs and restraining the recombination rate of charge carriers. As a result, the photocatalytic activity of the composites was enhanced in comparison with pure CNNs and VONRs. The photocatalytic efficiency of optimal composite (4-VONRs/CNNs) for the removal of CR (Cr (VI)) was about 9.33 (4.22) and 73.52 (19.2) times higher than that of pure CNNs and VONRs, respectively. Meanwhile, the 4-VONRs/CNNs exhibited good photocatalytic stability in recycling experiments. Such enormous enhancement in photocatalytic performance was predominantly ascribed to the efficient separation and transfer of photogenerated electron-hole pairs at the VONRs/CNNs interface imparted through the direct Z-scheme charge carrier migration mechanism. Moreover, the energy band structure and the quenching effects of different scavengers demonstrated that the electrons of CNNs and holes of VONRs with higher oxidizability and reducibility are the real participants in photocatalytic reactions.