Ultrasonic-assisted synthesis of lignin-capped Cu2O nanocomposite with antibiofilm properties.

Under ultrasonication, cuprous oxide (Cu2O) microparticles (<5 µm) were fragmented into nanoparticles (NPs, ranging from 10 to 30 nm in diameter), and interacted strongly with alkali lignin (Mw = 10 kDa) to form a nanocomposite. The ultrasonic wave generates strong binding interaction between lignin and Cu2O. The L-Cu nanocomposite exhibited synergistic effects with enhanced antibiofilm activities against E. coli, multidrug-resistant (MDR) E. coli, S. aureus (SA), methicillin-resistant SA, and P. aeruginosa (PA). The lignin-Cu2O (L-Cu) nanocomposite also imparted notable eradication of such bacterial biofilms. Experimental evidence unraveled the destruction of bacterial cell walls by L-Cu, which interacted strongly with the bacterial membrane. After exposure to L-Cu, the bacterial cells lost the integrated structural morphology. The estimated MIC for biofilm inhibition for the five tested pathogens was 1 mg/mL L-Cu (92 % lignin and 8 % Cu2ONPs, w/w %). The MIC for bacterial eradication was noticeably lower; 0.3 mg/mL (87 % lignin + 13 % Cu2ONPs, w/w %) for PA and SA, whereas this value was appreciably higher for MDR E. coli (0.56 mg/mL, 86 % lignin and 14 % Cu2O NPs). Such results highlighted the potential of L-Cu as an alternative to neutralize MDR pathogens.

Naturally Derived Carbon Dots In Situ Confined Self-Healing and Breathable Hydrogel Monolith for Anomalous Diffusion-Driven Phytomedicine Release.

Fluorescent nanocarbons are well-proficient nanomaterials because of their optical properties and surface engineering. Herein, Apium graveolens-derived carbon dots (ACDs) have been synthesized by a one-step hydrothermal process without using any surplus vigorous chemicals or ligands. ACDs were captured via an in situ gelation reaction to form a semi-interpenetrating polymer network system showing mechanical robustness, fluorescent behavior, and natural adhesivity. ACDs-reinforced hydrogels were tested against robust uniaxial stress, repeated mechanical stretching, thixotropy, low creep, and fast strain recovery, confirming their elastomeric sustainability. Moreover, the room-temperature self-healing behavior was observed for the ACDs-reinforced hydrogels, with a healing efficacy of more than 45%. Water imbibition through hydrogel surfaces was digitally monitored via "breathing" and "accelerated breathing" behaviors. The phytomedicine release from the hydrogels was tuned by the ACDs' microstructure regulatory activity, resulting in better control of the diffusion rate compared to conventional chemical hydrogels. Finally, the phytomedicine-loaded hydrogels were found to be excellent bactericidal materials eradicating more than 85% of Gram-positive and -negative bacteria. The delayed network rupturing, superstretchability, fluorescent self-healing, controlled release, and antibacterial behavior could make this material an excellent alternative to soft biomaterials and soft robotics.

Cuprous Oxide Nanoparticles Decorated Fabric Materials with Anti-biofilm Properties.

Considering the global spread of bacterial infections, the development of anti-biofilm surfaces with high antimicrobial activities is highly desired. This work unraveled a simple, sonochemical method for coating Cu2O nanoparticles (NPs) on three different flexible substrates: polyester (PE), nylon 2 (N2), and polyethylene (PEL). The introduction of Cu2O NPs on these substrates enhanced their surface hydrophobicity, induced ROS generation, and completely inhibited the growth of sensitive (Escherichia coli and Staphyloccocus aureus) and drug-resistant (MDR E. coli and MRSA) planktonic and biofilm. The experimental results confirmed that Cu2O-PE exhibited complete biofilm mass reduction ability for all four strains, whereas Cu2O-N2 showed more than 99% biomass inhibition against both drug-resistant and sensitive pathogens in 6 h. Moreover, Cu2O-PEL also indicated a 99.95, 97.73, 98.00, and 99.20% biomass reduction of MRSA, MDR E. coli, E. coli, and S. aureus, respectively. All substrates were investigated for time-dependent inhibitions, and the associated biofilm mass and log reduction were evaluated. The mechanisms of Cu2O NP action against the mature biofilms include the generation of reactive oxygen species (ROS) as well as electrostatic interaction between Cu2O NPs and bacterial membranes. The current study could pave the way for the commercialization of sonochemically coated Cu2O NP flexible substrates for the prevention of microbial contamination in hospitals and industrial environments.

Cellulose Nanocrystals (CNC)-Based Functional Materials for Supercapacitor Applications.

The growth of industrialization and the population has increased the usage of fossil fuels, resulting in the emission of large amounts of CO2. This serious environmental issue can be abated by using sustainable and environmentally friendly materials with promising novel and superior performance as an alternative to petroleum-based plastics. Emerging nanomaterials derived from abundant natural resources have received considerable attention as candidates to replace petroleum-based synthetic polymers. As renewable materials from biomass, cellulose nanocrystals (CNCs) nanomaterials exhibit unique physicochemical properties, low cost, biocompatibility and biodegradability. Among a plethora of applications, CNCs have become proven nanomaterials for energy applications encompassing energy storage devices and supercapacitors. This review highlights the recent research contribution on novel CNC-conductive materials and CNCs-based nanocomposites, focusing on their synthesis, surface functionalization and potential applications as supercapacitors (SCs). The synthesis of CNCs encompasses various pretreatment steps including acid hydrolysis, mechanical exfoliation and enzymatic and combination processes from renewable carbon sources. For the widespread applications of CNCs, their derivatives such as carboxylated CNCs, aldehyde-CNCs, hydride-CNCs and sulfonated CNC-based materials are more pertinent. The potential applications of CNCs-conductive hybrid composites as SCs, critical technical issues and the future feasibility of this endeavor are highlighted. Discussion is also extended to the transformation of renewable and low-attractive CNCs to conductive nanocomposites using green approaches. This review also addresses the key scientific achievements and industrial uses of nanoscale materials and composites for energy conversion and storage applications.

Exploring differences in the physicochemical, functional, structural, and pasting properties of banana starches from dessert, cooking, and plantain cultivars (Musa spp.).

Banana starch, with its nutritional and functional properties, opens up new opportunities for the food industry, which is seeking new starch sources to fulfil rising demand. Herein, physico-chemical, and functional properties of banana starches isolated from dessert, plantain, and cooking cultivars were investigated. Starch yield was higher in Popoulu (30.58%) and Monthan (27.82%). Starch granules registered irregular forms with granule sizes ranging from 8.9 to 55.09 µm. Among the cultivars, the amylose content was ranged between 25.05 and 31.86%. Total starch (95.86 and 95.60%,) and resistant starch (65.56 and 59.20%) were higher in Saba and Monthan respectively. Flour colour index (86.2-90.6) was higher in banana starches. Differential scanning calorimetry and rapid viscosity studies confirmed that starches from Saba (87.67 and 85.71 °C) Monthan (85.36 and 81.65 °C) have a higher gelatinization property. Banana starches were B and C-type with varying crystallinity levels (21.19-52.01%). The in-vitro starch digestibility revealed that Saba starch has a lower hydrolysis rate with lesser glycemic index. PCA showed the greater impact of amylose and resistant starch content on the grouping of varieties. These findings would be useful for food and non-food industries in terms of using banana starch in various food compositions and other industrial applications.

Microbial inhibition and biosensing with multifunctional carbon dots: Progress and perspectives.

Carbon dots (CDs) and their doped counterparts including nitrogen-doped CDs (N@CDs) have been synthesized by bottom-up or top-down approaches from different precursors. The attractiveness of such emerging 2D­carbon-based nanosized materials is attributed to their excellent biocompatibility, preparation, aqueous dispersibility, and functionality. The antimicrobial, optical, and electrochemical properties of CDs have been advocated for two important biotechnological applications: bacterial eradication and sensing/biosensing. CDs as well as N@CDs act as antimicrobial agents as their surfaces encompass functional hydroxyl, carboxyl, and amino groups that generate free radicals. As a new class of photoluminescent nanomaterials, CDs can be employed in diversified analytics. CDs with surface carboxyl or amino groups form nanocomposites with nanomaterials or be conjugated with biorecognition molecules toward the development of sensors/biosensors. The deployment of conductive CDs in electrochemical sensing has also increased significantly because of their quantum size, excellent biocompatibility, enzyme-mimicking activity, and high surface area. The review also addresses the ongoing challenges and promises of CDs in pathogenesis and analytics. Perspectives on the future possibilities include the use of CDs in microbial viability assay, wound healing, antiviral therapy, and medical devices.

Facile ultrasonic preparation of a polypyrrole membrane as an absorbent for efficient oil-water separation and as an antimicrobial agent.

Polypyrrole (PPY) spherical particles synthesized using carbon dots as an efficient catalyst were strongly embedded on fluorinated nonwoven fabric by ultrasonication to form a membrane with high hydrophilicity. An optimal amount of PPY adhered to the membrane after 30 min of sonication enhanced the overall membrane area with high hydrophilicity. Oil with high hydrophobicity was repelled by the resulting membrane, whereas water was freely penetrated and diffused from the membrane. The membrane exhibited good reusability and efficiency for the recovery of oil from a cooking oil-water mixture within 30 s. The incorporation of PPY in the fluorinated fabric imparts significant antibacterial properties against two common pathogens, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The anti-biofouling membrane could pave the way for its potential application to separate spilled oil from contaminated waters, comprising different microorganisms and living species. The novelty of this manuscript is described in a new system, the fabrication of PPY membranes with two important properties: biocidal and oil/water separation.

Photocatalytic Degradation of Organic Dyes and Antimicrobial Activities by Polyaniline-Nitrogen-Doped Carbon Dot Nanocomposite.

Nitrogen-doped carbon nanodots (N@CDs) were prepared by hydrothermal processing of bovine serum albumin (Mw: 69,324 with 607 amino acids). A polyaniline (PANI-N@CDs) nanocomposite was then synthesized by ultrasonication and used to degrade Congo red (CR), methylene blue (MB), Rhodamine B (RhB), and crystal violet (CV) four common organic dyes. The PANI-N@CD nanocomposite simultaneously adsorbed and concentrated the dye from the bulk solution and degraded the adsorbed dye, resulting in a high rate of dye degradation. The combination of holes (h+), hydroxyl (OH•), and O2•- was involved in the N@CD-mediated photocatalytic degradation of the dyes. Under visible light illumination at neutral pH, the PANI-N@CDs were proven as an efficient adsorbent and photocatalyst for the complete degradation of CR within 20 min. MB and RhB were also degraded but required longer treatment times. These findings supported the design of remediation processes for such dyes and predicted their fate in the environment. The nanocomposite also exhibited antimicrobial activities against Gram-negative bacterium E. coli and Gram-positive bacterium S. aureus.

Effect of fins and silicon dioxide nanoparticle black paint on the absorber plate for augmenting yield from tubular solar still.

The present study aims at enhancing the yield of tubular solar still (TSS) by employing fins and coating the absorber plate. We doped the SiO2 nanoparticles into black paint at the weight concentration ranging from 10 to 40%. The solar still was tested in a bright sunny climatic condition of Chennai, Indian (lat. 13° 08' N and long. 80° 27' E). Under transient heat flux conditions, water, basin, and TSS glass temperatures with and without fin were measured. The rate of heat transfer by convection between the water and absorber plate was increased. Results revealed that the basin and water temperatures were improved by 10.49% and 10.88%, respectively when using black paint with SiO2 nanoparticle in the concentration of 20%, coated on the absorber plate compared to that when using the ordinary black paint, while using the fins on the absorber plate enhanced the potable water produced by 55.18% when using 20% SiO2 nanoparticle compared to that of conventional TSS. The cost per liter of water produced using the flat and finned absorber coated using 20% SiO2 nanoparticle in black paint is found as 0.0187 and 0.012 $/L respectively.

Green Synthesis of Multifunctional Carbon Dots with Antibacterial Activities.

Carbon dots (CDs) were obtained from medicinal turmeric leaves (Curcuma longa) by a facile one-step hydrothermal method and evaluated for their bactericidal activities against two gram-negative; Escherichia coli, Klebsiella pneumoniae, and two gram-positive counterparts; Staphylococcus aureus, S. epidermidis. The CDs exhibited spherical shapes with a mean size of 2.6 nm. The fluorescence spectra of CDs revealed intense fluorescence at λex/em = 362/429 nm with a bright blue color in an aqueous solution. The CDs showed strong photostability under various environmental conditions (pH, salt, and UV-radiation). The complete bactericidal potency of CDs was 0.25 mg/mL for E.coli and S. aureus after 8 h of exposure, while for K. pneumoniae, and S. epidermidis, the CDs at 0.5 mg/mL good antibacterial effect within 8 h and complete eradication after 24 h of exposure is observed. The release of reactive oxygen species played a crucial role in the death of the bacterial cell. The present study provides a strategy for the preparation of CDs from a medicinal plant and their potential antibacterial activities against four common contagious pathogens.

Antimicrobial Properties of the Polyaniline Composites against Pseudomonas aeruginosa and Klebsiella pneumoniae.

CuO, TiO2, or SiO2 was decorated on polyaniline (PANI) by a sonochemical method, and their antimicrobial properties were investigated for two common Gram-negative pathogens: Pseudomonas aeruginosa (PA) and Klebsiella pneumoniae (KP). Without PANI, CuO, TiO2, or SiO2 with a concentration of 220 µg/mL exhibited no antimicrobial activities. In contrast, PANI-CuO and PANI-TiO2 (1 mg/mL, each) completely suppressed the PA growth after 6 h of exposure, compared to 12 h for the PANI-SiO2 at the same concentration. The damage caused by PANI-SiO2 to KP was less effective, compared to that of PANI-TiO2 with the eradication time of 12 h versus 6 h, respectively. This bacterium was not affected by PANI-CuO. All the composites bind tightly to the negative groups of bacteria cell walls to compromise their regular activities, leading to the damage of the cell wall envelope and eventual cell lysis.

Antimicrobial Properties of Polyaniline and Polypyrrole Decorated with Zinc-Doped Copper Oxide Microparticles.

Polyaniline (PANI) and polypyrrole (PPY) were synthesized by carbon dots (CDs) under UV irradiation and then sonicated together with zinc acetate and copper acetate to form the PANI-Zn@CuO and PPY-Zn@Cu composites. The former consisted of agglomerated spherical particles with diameters of 1-5 µm, whereas the latter displayed irregular stick shapes with similar diameters. The bacterial potency of the composites against Escherichia coli and Staphylococcus aureus was enhanced remarkably with Zn doping in the CuO matrix, designated as Zn0.11Cu0.89O, at 0.144 mg/mL. The cell death was mainly attributed to the release of reactive oxygen species (ROS) that would severely damage DNA, proteins, and lipids. Bacteria could adhere to neutral surfaces of the composites by van der Waals attractive forces. The binding event disrupted the native surface charge of bacterial cells to induce cell lysis and result in eventual cell death.

Applications of N-Doped Carbon Dots as Antimicrobial Agents, Antibiotic Carriers, and Selective Fluorescent Probes for Nitro Explosives.

The synthesis of nitrogen-doped carbon dots (N@CDs) was accomplished by a hydrothermal process using meta- phenylenediamine as a source of carbon and nitrogen. As prepared N@CDs exhibited bright blue color fluorescence emission (λex = 340 nm and λem = 420 nm) with a quantum yield of 12%. Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were eradicated by N@CDs with a minimum inhibition concentration (MIC) of 1 and 0.75 mg/mL, respectively. The N@CDs were also proven as nanovesicles for drug molecules where the drug release displayed a sustained time-dependent profile at the physiological condition. The release of ciprofloxacin as a model drug was governed by the Korsmeyer-Peppas model, indicating ∼60% of its release from the N@CD conjugated drug system at the physiological pH. Selective analysis of trinitrophenol (TNP), a popular explosive, was achieved by fluorescence quenching of N@CDs, compared favorably with other nitrophenols. An estimated detection limit of TNP was 2.45 µM with a linear response spanning from 1 to 75 µM.

Can Be a Bimetal Oxide ZnO-MgO Nanoparticles Anticancer Drug Carrier and Deliver? Doxorubicin Adsorption/Release Study.

Bimetal oxide ZnO-MgO nanoparticles were synthesised by precipitation method at low temperature and characterised by analytical techniques such as XRD, SEM and FT-IR. In order to know the efficiency of uptake and release of anticancer drug, the adsorption and release of doxorubicin, on bimetal oxide nanoparticles was performed in dark room at room temperature. The adsorption models such as Henry, Freundlich and Langmuir models were validated with obtained experimental data. Due to heterogeneous surface of bimetal oxides, data followed well with Henry and Freundlich models but not Langmuir that proposed homogeneous adsorbent surface. The strong affinity between drug and nanoparticles is certainly due to the electrostatic interaction between positively charged doxorubicin molecules and negatively charged surface of ZnO-MgO nanoparticles and hydrogen bonding between them that confirmed from FT-IR analysis. The doxorubicin release from ZnO-MgO nanoparticles was performed at pH 4 and 7 to evaluate the kinetic of drug release using various mathematical models. At neutral pH, the doxo release was found to be ~14% whereas at acidic pH (pH 4) nearly 68% of doxo was released at 6.5 hours due to dissolution and neutralising the surface charge of ZnO-MgO nanoparticles. Various mathematical models such as zero order, first order, Higuchi and Hixson-Crowell were approached to evaluate the kinetic release of drug from the nanoparticles. The obtained release data for acidic pH followed Hixson-Crowell model, proposes erosion dependent release system, compared to Higuchi that confirmed doxo release is due to dissolution of ZnO-MgO nanoparticles. In this study, it is concluded that ZnO-MgO nanoparticles will be a promising drug vehicle in drug delivery system.

Graphene Oxide Synthesis from Agro Waste.

A new method of graphene oxide (GO) synthesis via single-step reforming of sugarcane bagasse agricultural waste by oxidation under muffled atmosphere conditions is reported. The strong and sharp X-ray diffraction peak at 2θ = 11.6° corresponds to an interlayer distance of 0.788 nm (d002) for the AB stacked GOs. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) confirm the formation of the GO layer structure and the hexagonal framework. This is a promising method for fast and effective synthesis of GO from sugarcane bagasse intended for a variety of energy and environmental applications.