•A variety of strategies for controlling doping in graphene are summarized.•Dynamic doping modulation by external stimuli is introduced.•The underlying principles to control Fermi level in graphene ...are described.
Graphene is one of the most promising materials for post-silicon electronics and has outstanding physical and electronic properties. In particular, its unique 2D sp2-hybridized networks of carbon atoms arranged in a honeycomb lattice make graphene potential for exceptional electronic quality. However, in order to use graphene in possible applications such as photodetector, photovoltaics, sensors, organic light-emitting diodes, organic thin-film transistors, supercapacitor, and catalytic applications, it is essential to precisely modulate its electronic properties, i.e. doping. In this review, we present various strategies for engineering the Fermi level in graphene, including heteroatom substitution, molecular adsorption, introducing functional molecules for external stimuli responsiveness. We anticipate that the current review provides a concise information on the methods to probe doping level, effective doping approaches, and achievable doping type and charge carrier concentration ranges so that an appropriate doping approach can be readily designed.
•Synthesis of TiO2/AgNP nanoparticles by dopamine hydrochloride.•Incorporation of TiO2/AgNP nanoparticles into cellulose acetate nanofibers.•The CA/TiO2/AgNP nanofibers fabricated for long term ...excellent antibacterial uses.•The CA/TiO2/AgNP nanofibers are expected to reduce chances of argyria and argyrosis.•The CA/TiO2/AgNP nanofibers depicted antibacterial properties for upto 72 h.
Silver nanoparticles (AgNPs) are effective antimicrobial agents however excess release of silver causes argyria and argyrosis. An strategy to avoid these detrimental side effects is immobilization of AgNPs on several organic and inorganic substrates. Herein, we propose immobilization of AgNPs on TiO2 nanoparticles by an environmentally green process subsequently incorporating the TiO2/AgNP into cellulose acetate (CA) nanofiber matrix. The TiO2/AgNP nanocomposite particles were prepared by coating TiO2 nanoparticles with polydopamine hydrochloride followed by a treatment in AgNO3 solution. Subsequently, the TiO2/AgNP nanocomposites were added into CA solution and electrospun to fabricate CA/TiO2/AgNP composite nanofibers. The samples were characterized by XRD, TEM, XPS, SEM, EDX, FTIR and antibacterial assays. Synthesis of TiO2/AgNP and its loading into CA nanofibers was confirmed by XRD, XPS, TEM and EDX analysis. SEM images indicated regular morphology of the nanofibers. The antibacterial test results confirmed CA/TiO2/AgNP composite nanofibers having excellent antibacterial performances for 36 h and substantial bacterial growth inhibition for 72 h.
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•Pyrogallol conjugation of chitosan on primary amine increase the solubility at physiological pH.•Pyrogallol tailored chitosan exhibits improved wet adhesion than commercially ...available tissue sealant -fibrin glue.•Chitosan-gallic acid hydrogel can be used for microfiber fabrication via electrospinning to mimic natural structure.•Pyrogallol functionalization improved hemostasis function than parent chitosan.
The nature-inspired fabrication of tissue adhesive and hemostatic hydrogels holds great potential for restoring damaged internal tissue in regenerative medicine. However, feeble adhesion, multifaceted systems, prohibitive costs, and toxicity impede their applications in the medical field. In order to solve this problem, we fabricated chitosan-based wet tissue adhesive with hemostatic functions inspired by the self-healing mechanism of the tunicate. In order to introduce pyrogallol moiety, gallic acids, which are broadly distributed in nature, were incorporated into chitosan backbone, a key residue for the self-healing process of tunichrome in tunicates. The in vitro adhesion test results of the tunicate-inspired hydrogel exhibited two-fold greater adhesion ability in wet condition than did fibrin glue, a commercially available surgical glue. Further, the tunicate-inspired hydrogel exhibited significantly more platelet adhesion and blood clotting ability than the parent polymer. We also demonstrated the ability of the derivative to completely mimic the tunicate’s fibrous structure by fabricating an electrospun mat. The hemostatic function vis-à-vis the wet adhesiveness of the synthesized chitosan-based material may be useful for facilitating the shortcomings of the restorative tissue medicine. Additionally, the electrospinning capability will enable the modulate of the structure-property relationship and a three-dimensional design for its application site.
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•The porous aerogels have low density and high porosity.•The aerogels exhibit excellent absorptive capacity of oil and reusability.•The chlorinated aerogels show excellent ...antibacterial property against bacteria.•The as-prepared aerogels have potential application in water treatment.
An N-halamine precursor monomer, cyanuric chloride (CYCH), was attached onto nanocrystalline cellulose (NCC) and chloropropyltriethoxysilane (CPTES) was used as a crosslinking agent to prepare hydrogels based on the modified nanocrystalline cellulose. The aerogels were obtained by freeze-drying the hydrogels followed by chlorination. Microscopic investigation of the morphology revealed that the aerogels were porous with three-dimensional web-like microstructure. Their hydrophobic properties were efficient in removing dodecane spills from water. The response of the chlorinated aerogels challenged against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) showed their potent antimicrobial activities in killing these two bacterial species. Their properties of being ultralight, highly porous, hydrophobic, reusable, superabsorbing, and antibacterial efficient render these aerogels promising materials for cleaning up oil spills and inactivating bacteria.
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•Ag/cellulose nanofibers before (CMC-Ag) and after (AgNPs/CMC) reduction are prepared.•Physicochemical properties of CMC-Ag and AgNPs/CMC are investigated.•Content and release of Ag ...were higher in CMC-Ag than AgNPs/CMC.•Better antibacterial activity is concluded by CMC-Ag in comparison to AgNPs/CMC.
Herein, we report a comparative study of silver coated anionic cellulose nanocomposite before (CMC-Ag) and after (AgNPs/CMC) chemical reduction for antibacterial activity. Cellulose nanofibers were prepared by deacetylation of electrospun cellulose acetate nanofibers, which were then treated with sodium chloroacetate to prepare anionic cellulose nanofibers (CMC). Aqueous AgNO3 solution with different concentrations was employed to produce nanofiber composites. To obtain AgNPs/CMC, the resultant Ag/CMC nanofibers were chemically reduced with NaBH4. The nanocomposites were characterized by FE-SEM, FTIR, XPS and SEM-EDS. Antimicrobiality tests were conducted using S. aureus and Escherichia coli bacteria following standard test method JIS L1902, 2008. The EDS results confirmed higher silver content in CMC-Ag nanofibers than AgNPs/CMC nanofibers. The antimicrobial test and EDS results demonstrated higher silver release (larger halo width) by the former in comparison to later which confers better antimicrobiality by CMC-Ag nanofibers.
•Thiol functionalization on cellulose nanofiber surface imparting ability to adsorb metal ions.•Adsorption occurring only on the surface with homogeneously distributed adsorption energy.•Kinetic ...studies revealing the role of surface thiol in metal ion adsorption mechanism.•Expandability of cellulose for biocompatible, nontoxic, and sustainable water purification membrane applications.
This work reports the fabrication of a thiol-functionalized cellulose nanofiber membrane that can effectively adsorb heavy metal ions. Thiol was incorporated onto the surface of cellulose nanofibers, which were fabricated by the deacetylation of electrospun cellulose acetate nanofibers and subsequent esterification of a thiol precursor molecule. Adsorption mechanism was investigated using adsorption isotherms. Adsorption capacity as a function of adsorbate concentration was described well with Langmuir isotherm, suggesting that metal ions form a surface monolayer with a homogenously distributed adsorption energy. Maximum adsorption capacities in the Langmuir isotherm for Cu(II), Cd(II), and Pb(II) ions were 49.0, 45.9, and 22.0 mg·g−1, respectively. The time-dependent adsorption capacities followed a pseudo-second-order kinetic model, suggesting that chemisorption of each doubly charged metal ion occurs with two thiol groups on the surface. These results highlight the significance of surface functionality on biocompatible, nontoxic, and sustainable cellulose materials to expand their potential and applicability towards water remediation applications.
Herein, the review aims to compile some reportable work of researchers carried concerning the use of nanomaterials in the polymeric composites for significant improvements in the properties and to ...report the application areas of such nanocomposites. Carbon nanotubes, cellulose nanoparticles, titanium dioxide, and other nanoparticles are used in the polymeric composites to enhance their mechanical, electrical, inter-laminar, optical, chemical, electrochemical, electromagnetic shielding, and ballistic properties. Such nanocomposites have a wide range of applications in structural, biomedical, electronics, automobiles, aircraft, oil pipelines, gas pipeline construction, electromagnetic shielding, and protected areas. According to the reported results of researchers, the incorporation of nanomaterials into polymers significantly enhance their properties, which make them able to widen their application areas.
The biological performance of artificial biomaterials is closely related to their structure characteristics. Cell adhesion, migration, proliferation, and differentiation are all strongly affected by ...the different scale structures of biomaterials. Silk fibroin (SF), extracted mainly from silkworms, has become a popular biomaterial due to its excellent biocompatibility, exceptional mechanical properties, tunable degradation, ease of processing, and sufficient supply. As a material with excellent processability, SF can be processed into various forms with different structures, including particulate, fiber, film, and three-dimensional (3D) porous scaffolds. This review discusses and summarizes the various constructions of SF-based materials, from single structures to multi-level structures, and their applications. In combination with single structures, new techniques for creating special multi-level structures of SF-based materials, such as micropatterning and 3D-printing, are also briefly addressed.
Bacteria free clean air is important for healthy life. Current research is mainly focused on nonwoven and antibacterial breath mask development. Copper oxide was selected as antibacterial agent due ...to its good antimicrobial properties as well as its production is economical as compared to other metallic nanoparticles which are being used as antibacterial agents i.e. Copper nanoparticles, gold nanoparticles, and silver nanoparticles. Copper (II) oxide is hydrophilic in nature and is one of the two stable oxides of copper. Prepared nanofibers were characterized for possible testing which include morphological characterization, surface area and porosity measurement using BET, mechanical properties using Universal Testing Machine, elemental analysis using XPS, crystallinity assessment by XRD, breathability test by upright cup method, air permeability test, thermal analysis by TGA, and antimicrobial properties by disk diffusion method. Drug release properties were assessed by ICP. Presence of copper oxide nanoparticles exhibited excellent morphological, mechanical, structural, surface, and antimicrobial properties (samples having 1.00% CuO exhibited optimum results).
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•Antibacterial property of copper oxide.•Copper II oxide was loaded on electrospinning for the first time.•Addition of copper II oxide imparted tensile strength to base polymer (Polyacrylonitrile).•Good performance for breathability.
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