Significant improvements in mechanical property and water stability of chitosan by carbon nanotubes

Recent Advances in Engineering of 2D Materials-Based Heterostructures for Electrochemical Energy Conversion

2D materials, such as graphene, transition metal dichalcogenides, black phosphorus, layered double hydroxides, and MXene, have exhibited broad application prospects in electrochemical energy conversion due to their unique structures and electronic properties. Recently, the engineering of heterostructures based on 2D materials, including 2D/0D, 2D/1D, 2D/2D, and 2D/3D, has shown the potential to produce synergistic and heterointerface effects, overcoming the inherent restrictions of 2D materials and thus elevating the electrocatalytic performance to the next level. In this review, recent studies are systematically summarized on heterostructures based on 2D materials for advanced electrochemical energy conversion, including water splitting, CO2 reduction reaction, N2 reduction reaction, etc. Additionally, preparation methods are introduced and novel properties of various types of heterostructures based on 2D materials are discussed. Furthermore, the reaction principles and intrinsic mechanisms behind the excellent performance of these heterostructures are evaluated. Finally, insights are provided into the challenges and perspectives regarding the future engineering of heterostructures based on 2D materials for further advancements in electrochemical energy conversion.

Incorporation of chitosan/graphene oxide nanocomposite in to the PMMA bone cement: Physical, mechanical and biological evaluation

One of the most popular types of bone cements is polymethylmethacrylate (PMMA). The properties of this bone cement have attracted many researchers effort to modify its properties. In this study, after preparation of chitosan (Cs) powder and Cs/graphene oxide (GO) nanocomposite powder, they were added homogeneously to the PMMA bone cement with different percentages. The results showed that the addition of 25 wt% of Cs/GO nanocomposite powder to the PMMA bone cement cause to increase the compressive strength by 16.2%, the compressive modulus by 69.1% and the bending strength by 24.0%. The obtained results showed that by adding Cs/GO nanocomposite powder to the PMMA bone cement, setting time and injectability were increased, maximum temperature was decreased and apatite-like deposition was increased after 4 weeks of incubation in SBF solution. The results of MG-63 cell culture confirmed the improvement of cell viability, growth and cell adhesion for 25 wt% PMMA-Cs/GO composite bone cement. Therefore, it can be concluded that 25 wt% PMMA-Cs/GO composite bone cement with improved mechanical, physical and biological properties can be a good replacement for common commercial bone cements in orthopedic applications.

Cu(II)-Regulated On-Site Assembly of Highly Chemiluminescent Multifunctionalized Carbon Nanotubes for Inorganic Pyrophosphatase Activity Determination

A novel signal-on chemiluminescence (CL) assay for pyrophosphatase (PPase) activity determination was innovatively developed based on the Cu(II)-regulated on-site assembly of highly chemiluminescent Cu(II), N-(aminobutyl)-N-(ethylisoluminol) (ABEI), gold nanodot, and chitosan multifunctionalized carbon nanotubes (Cu(II)/ABEI-Au/cs-CNTs). First, ABEI-functionalized gold nanodots (ABEI-Au) were assembled on the surface of chitosan-modified carbon nanotubes (cs-CNTs) via the reduction of HAuCl₄ with ABEI in a cs-CNT suspension to form ABEI-Au/cs-CNTs. Then, it was found that the catalyst Cu(II) can be selectively, efficiently, and quickly adsorbed onto ABEI-Au/cs-CNTs via the high-affinity interactions between Cu(II) and cs-CNTs to form novel hybrid nanomaterials Cu(II)/ABEI-Au/cs-CNTs. The CL intensity of Cu(II)/ABEI-Au/cs-CNTs was enhanced by about 2 orders of magnitude compared with that of ABEI-Au/cs-CNTs. Furthermore, it was found that in the presence of pyrophosphate ions (PPi), PPi could coordinate with Cu(II) to form a stable PPi-Cu(II) complex and block the assembly of Cu(II)/ABEI-Au/cs-CNTs. After the addition of PPase, PPase could catalyze the hydrolysis of PPi into Pi and release Cu(II) from the PPi-Cu(II) complex. The released free Cu(II) could trigger the on-site assembly of highly chemiluminescent Cu(II)/ABEI-Au/cs-CNTs, resulting in an enhanced CL intensity. The enhanced CL intensity had a good linear relationship with the activity units of PPase ranging from 0.025 to 0.5 U, with a detection limit of 9 mU. The method was employed to monitor the PPase inhibitor efficiently. Cu(II)/ABEI-Au/cs-CNTs with excellent CL may also find more applications in the development of novel CL analytical methods.

Biocompatible and mechanically robust nanocomposite hydrogels for potential applications in tissue engineering

The synergistic contributions of nanofillers and polymer matrix induce remarkable properties in nanocomposite hydrogels. Present article reports the facile synthesis of biocompatible nanocomposite hydrogels using microporous multi wall carbon nanotubes (MWCNTs) dispersed chitosan (CH)-Acrylonitrile (AN), N,N'-methylenebisacrylamide (MBAAm) and linseed polyol through solution blending method. Polyol and N,N'-methylenebisacrylamide (MBAAm) was used as the crosslinking agent. The structural characterization and formation of highly crosslinked network with dendrimer morphology was confirmed by FT-IR and scanning electron microscope (SEM) analysis. In addition, transmission electron microscope (TEM) was employed to visualize the size and proper dispersion of MWCNT in the polymer matrices. The strong mechanical strength exhibited by these hydrogel films was confirmed by the tensile strength analysis. The dispersion of the conductive nanofillers, like MWCNTs has significantly enhanced the strength, which revealed unique characteristics of these hydrogel films. The high swelling capacity and sustained expansion of hydrogel films were confirmed in the buffer solutions of pH4 and 7.4. The biodegradability of these films was estimated by hydrolytic and soil burial tests. The biocompatibility test was conducted on Human Embryonic Kidney (HEK-293) cell line, which confirmed the non-toxic and biocompatible nature of these films. Incorporation of carbon nanotubes (MWCNTs) in the polymer matrix enhanced the film forming properties, high modulus and tensile strength, swelling ability, biodegradable and biocompatibility. These properties can be finely tuned through the variation of MWCNT concentrations, as a result these nanostructure hydrogel films have potential scope for their diverse applications in the field of tissue engineering.

Significant improvements in the mechanical properties of chitosan functionalized carbon nanotubes/epoxy composites

TEM image of the fracture structure of CNTs/CS/EP.

Eco-friendly synthesis and catalytic application of chitosan/gold/carbon nanotube nanocomposite films

Novel eco-friendly chitosan nanocomposite membranes containing gold nanoparticles and carbon nanotubes (CNTs) have been synthesized to produce reusable catalytic membranes.

A porous hybrid imprinted membrane for selectively anchoring target proteins from a complex matrix

The proposed route for the polymerization of CP/CNT/DA-MIM (A) and the recognition protocol of CP/CNT/DA-MIM (B).

High-density assembly of chemiluminescence functionalized gold nanodots on multiwalled carbon nanotubes and their application as biosensing platforms

A one-step strategy was developed for high-density assembly of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) functionalized gold nanodots onto the sidewalls of chitosan-grafted multiwalled carbon nanotubes (cs-MWCNTs) via the reduction of HAuCl4 with ABEI in the presence of cs-MWCNTs, resulting in novel hybrid nanomaterials with excellent chemiluminescence and electrochemiluminescence properties.

Synthesis, characterization and stability of chitosan and poly(methyl methacrylate) grafted carbon nanotubes

The single walled carbon nanotubes (CNTs) were effectively functionalized through grafting with chitosan (CTS) and poly(methyl methacrylate) (PMMA). Prior to grafting reaction, the carboxylated SWNCTs (SWNCTs-COOH) were obtained by treating pristine CNTs with a mixture of 3:1 (v/v) H(2)SO(4) and HNO(3), and the successive treatment of SWNCTs-COOH with SOCl(2) yielded the acylated CNTs (CNTs-COCl). The functionalized derivatives of CNTs were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Both CTS and PMMA grafted CNTs showed better dispersability in acetic acid and tetrahydrofuran, in addition to higher stability in solution.

Stabilisation of SWNTs by alkyl-sulfate chitosan derivatives of different molecular weight: towards the preparation of hybrids with anticoagulant properties

We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which presents important pharmacological properties, can suspend single walled carbon nanotubes (SWNTs) up to 20 times more effectively than other chitosan derivatives in an aqueous environment. In an attempt to further investigate the impact of different molecular weights of chitosan to the solubilization and anticoagulant properties of these hybrids an array of NOSC derivatives varying their molecular weight (low, medium and high respectively) was synthesised and characterised by means of FT-IR spectroscopy, NMR spectroscopy and thermal gravimetric analysis (TGA). Microwave and nitric acid purified SWNTs, characterised by FT-IR spectroscopy, transmission electron microscopy (TEM) and Raman spectroscopy, were colloidally stabilised by these polymers and their anticoagulant activity was assessed. The results revealed that the low molecular weight NOSC coated SWNTs exhibit the highest activity when 0.5 mg mL(-1) NOSC solutions are used, activity which is similar to that of the free polymer. Preliminary studies by exposure of these hybrids to Brine Shrimp (Artemia) cysts revealed no effect on the viability of sub-adult Artemia. Our findings suggest the possibility of tailoring these nanomaterials to bear the required properties for application as biocompatible building blocks for nanodevices including biosensors and biomaterials.

Biobased nanocomposites from layer-by-layer assembly of cellulose nanowhiskers with chitosan

A new biodegradable nanocomposite was obtained from layer-by-layer (LBL) technique using highly deacetylated chitosan and eucalyptus wood cellulose nanowhiskers (CNWs). Hydrogen bonds and electrostatic interactions between the negatively charged sulfate groups on the whisker surface and the ammonium groups of chitosan were the driving forces for the growth of the multilayered films. The film growth was followed by UV-vis spectroscopy through the maximum value of the absorption band at 194 nm and showed the deposition of 14.7 mg.m(-2) of chitosan polymer in each cycle. Scanning electron microscopy showed high density and homogeneous distribution of CNWs adsorbed on each chitosan layer. Cross-section characterization of the assembled films indicates an average of approximately 7 nm of thickness per bilayer. The results presented in this work indicate that the methodology used can be extended to different biopolymers for the design of new biobased nanocomposites in a wide range of applications such as biomedical and food packaging.

Advances in biomimetic and nanostructured biohybrid materials

The rapid increase of interest in the field of biohybrid and biomimetic materials that exhibit improved structural and functional properties is attracting more and more researchers from life science, materials science, and nanoscience. Concomitant results offer valuable opportunities for applications that involve disciplines dealing with engineering, biotechnology, medicine and pharmacy, agriculture, nanotechnology, and others. In the current contribution we collect recent illustrative examples of assemblies between materials of biological origin and inorganic solids of different characteristics (texture, structure, and particle size). We introduce here a general overview on strategies for the preparation and conformation of biohybrids, the synergistic effects that determine the final properties of these materials, and their diverse applications, which cover areas as different as tissue engineering, drug delivery systems, biosensing devices, biocatalysis, green nanocomposites, etc.

Simple co-electrodeposition of functionalized multi-walled carbon nanotubes/chitosan composite coating on mainspring for enhanced modulus of elasticity

Co-electrodeposition of functionalized multi-walled carbon nanotubes (f-MWCNTs) with chitosan was performed on pieces of a stainless steel mainspring. Under moderate conditions, composite coatings with controllable thickness from a few hundred nanometers to tens of micrometers can be achieved. After coating an 8 microm composite layer on a piece of mainspring 120 microm thick (i.e. 6.7% increase in thickness), the Young's modulus of the mainspring was found to have increased by more than approximately 25%. Moreover, the coated mainsprings possess much stronger mechanical strength as demonstrated by fatigue tests. The significant enhancement of Young's modulus and intrinsic strength are mostly attributed to the effect exerted by the subtle combination of chitosan and MWCNT. In the current study, the intensive cross-linkages formed between the -COOH groups in f-MWCNTs and the hydroxyl (-OH) and amino (-NH2) groups in chitosan were exploited. The chitosan molecular chains and f-MWCNTs both chemically react and physically knot with each other, leading to a three-dimensional interlaced f-MWCNT/chitosan composite coating. The reported co-electrodeposition provides a simple approach to form a stable, reproducible and rigid f-MWCNTs composite coating, which leads to the realization of a high-performance mainspring with reinforced mechanical strength.

An electrochemical sensor for detection of laccase activities from Penicillium simplicissimum in compost based on carbon nanotubes modified glassy carbon electrode

An electrochemical sensor for detection of the activity of laccase from Penicillium simplicissimum isolated from the composting has been developed. The sensor is based on glassy carbon electrode modified with multi-wall carbon nanotubes (CNTs). The introduction of CNTs into this system can greatly enhance the electrochemical signal in this assay more sensitively, selectively and rapidly than that in conventional spectrophotometric assays. It was found that the optimal pH value of the electrolyte was 5.6. The results showed a good linear correlation between the current and the concentration of laccase activities measured by spectrophotometry, where the current slope was measured by chronoamperometry with a coefficient of 0.9835. Therefore, this electrochemical sensor can be used for rapid detection of laccase activity from P. simplicissimum. Furthermore, it may be potentially used for rapid quantification of P. simplicissimum according to the relationship between the laccase activities and the biomass.