Effects of Gamma Irradiation on Structural, Chemical, Bioactivity and Biocompatibility Characteristics of Bioactive Glass-Polymer Composite Film

Gamma irradiation is an effective technique for biocomposite films intended for application in tissue engineering (TE) to ensure sterility and patient safety prior to clinical applications. This study proposed a biocomposite film composed of natural polymer chitosan (CS) and synthetic polymer poly-Ɛ-caprolactone (PCL) reinforced with sol-gel-derived bioactive glass (BG) for potential application in TE. The BG/PCL/CS biocomposite film was sterilized using 25 kGy gamma rays, and subsequent changes in its characteristics were analyzed through mechanical and physical assessment, bioactivity evaluation via immersion in simulated body fluid (SBF) and biocompatibility examination using human primary dermal fibroblasts (HPDFs). Results indicated a homogeneous distribution of BG particles within the BG/PCL/CS polymer matrix which enhanced bioactivity, and the polymer blend provide a structurally stable film. Gamma irradiation induced an increase in the film's surface roughness due to photo-oxidative degradation; however, this did not adversely affect the integrity of glass particles and polymer chains. In vitro assessments demonstrated hydroxyapatite formation on the film's surface, suggesting bioactivity. Biocompatibility testing confirmed enhanced cell adhesion and proliferation. These multifunctional properties highlight the potential of the fabricated BG/PCL/CS biocomposite film for TE and regenerative medicine applications.

Functionalized electrospun nanofibers to enhance β-Galactosidase immobilization and catalytic activity for efficient galactooligosaccharide synthesis

This study aimed to immobilize β-galactosidase (β-GAL) into enhanced polystyrene (PS) electrospun nanofiber membranes (ENMs) with functionalized graphene oxide (GO). Initially, GO sheets were functionalized by salinization with 3-aminopropyl triethoxysilane (APTES). Then the ENMs (PS, PS/GO, and PS/GO-APTES) were prepared and characterized. Then, the β-GAL was immobilized in the different ENMs to produce the β-GAL-bound nanocomposites (PS-GAL, PS/GO-GAL, and PS/GO-APTES-GAL). Immobilization of β-GAL into PS/GO-APTES significantly improved enzyme adsorption by up to 87 %. Also, PS/GO-APTES-GAL improved the enzyme activity, where the highest enzyme activity was obtained at enzyme concentrations of 4 mg/L, 50 °C, and pH 4.5. Likewise, the storage stability and reusability of immobilized β-GAL were improved. Furthermore, this process led to enhanced catalytic behavior and transgalactosylation efficiency, where GOS synthesis (72 %) and lactose conversion (81 %) increased significantly compared to the free enzyme. Overall, the immobilized β-GAL produced in this study showed potential as an effective biocatalyst in the food industry.

Polyphenol modification of graphene-stabilized emulsions to form electrically conductive polymer spheres

HYPOTHESIS

Polyphenols, specifically tannic acid, should increase the hydrophilicity of graphene when added during the interfacial exfoliation through π-π stacking. Following Bancroft's rule, increasing the hydrophilicity of graphene will result in a phase inversion of water-in-oil emulsions stabilized by graphene. Polymerization of the oil phase will then lead to graphene-coated spheres rather than graphene-stabilized polyHIPEs.

EXPERIMENTS

Optical particle sizing, microscopy, contact angle, and electrical conductivity measurements were performed to determine the mechanism of sphere formation in graphene-stabilized emulsions modified with tannic acid. Studies focused on the effect of graphite flake size, graphite concentration, tannic acid concentration, and oil phase composition. Particle sizing and scanning electron microscopy examined the spheres' size, shape, and surface morphology. Contact angle measurements gave insight into the change in graphene surface energy. Conductivity studies examined the graphene shell surrounding the spheres.

FINDINGS

Adding tannic acid to graphene-stabilized emulsions induced a phase change from water-in-oil to oil-in-water. Contact angle measurements confirmed greater hydrophilicity of graphene in the presence of tannic acid. However, very high tannic acid concentrations led to a decrease in the stability of the emulsion. Varying the graphite flake size and concentration resulted in morphology and conductivity changes. Dilution of the monomer phase produced hollow microcapsules.

Efficient and stable electrorheological fluids based on chestnut-like cobalt hydroxide coupled with surface-functionalized carbon dots

Intrinsically polarized electrorheological fluids (ERFs) have better thermal stability than ERFs with polar molecules, so they have a broader application prospect. However, the electrorheological efficiency of the common intrinsically polarized ERF is still lower than 1500, which is related to the poor wettability between polarized materials and the continuous phase. Carbon dots (CDs) exhibit good stability, semiconductor properties and low toxicity. We prepared biomimetic chestnut-like cobalt hydroxide coupled with surface-functionalized CD particles (Co(OH)₂@CDs) by a simple hydrothermal method. Then we prepared an ERF by mixing Co(OH)₂@CDs with silicone oil and studied the effect of CDs on its rheology and electrorheology properties. The synergistic effect of the lipophilic groups on the surface of CDs and the biomimetic chestnut-like structure makes Co(OH)₂@CDs exhibit good wettability with silicone oil, and the optimal zero-field viscosity of Co(OH)₂@CDs-ERF is only 0.46 Pa s (particle mass fraction of 40%). Exceptional electrorheological efficiency (about 10 000, shear rate 0.1 s^-1, 5 kV mm^-1) and dynamic shear stress stability of optimal Co(OH)₂@CDs-ERF can be attributed to the dielectric enhancement of the biomimetic chestnut-like structure coupled with the semiconductor properties of CDs. In addition, Co(OH)₂@CDs-ERF has excellent anti-settling performance, outstanding thermal stability and low current density.

Synthesis and Electrorheological Response of Graphene Oxide/Polydiphenylamine Microsheet Composite Particles

Conducting graphene oxide/polydiphenylamine (GO/PDPA) microsheet nanocomposite particles were fabricated via in-situ oxidative polymerization using diphenylamine in the presence of GO. The morphological structures and dimensions of the fabricated GO/PDPA composites were evaluated using transmission electron microscopy and scanning electron microscopy. Electrorheological (ER) responses and creep behaviors of an ER fluid consisting of the GO/PDPA composites when suspended in silicone oil were evaluated using a rotational rheometer under input electric field. Three different types of yield stresses were examined along with dielectric analysis, demonstrating their actively tunable ER behaviors.

Preparation of core-shell structured metal-organic framework@PANI nanocomposite and its electrorheological properties

A novel core-shell-type electrorheological (ER) composite material was fabricated via using polyaniline as an insulating layer to the outer surface of the core conductive metal-organic framework (MIL-125) with controlled size and morphology. MIL-125 was firstly synthesized by a solvothermal method, and then polyaniline was synthesized in a polar solvent and a tight coating was successfully achieved to form a MIL-125@PANI core-shell nanocomposite. This core-shell structure greatly enhances the polarization ability of dispersed particles, thereby improving their rheological properties. The morphology of pure MIL-125 and MIL-125@PANI has been characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their structure was characterized by X-ray powder diffraction. Moreover, the ER activity of MIL-125-based and MIL-125@PANI-based ER fluids by dispersing the particles into silicone oil was studied using a rotational rheometer. The results show that the MIL-125@PANI composite particles have higher ER properties.

Recent development of electro-responsive smart electrorheological fluids

The characteristics of an electrorheological (ER) fluid, as a class of smart soft matter, can be actively and accurately tuned between a liquid- and a solid-like phase by the application of an electric field. ER materials used in ER fluids are electrically polarizable particles, which are attracting considerable attention in addition to further research. This perspective reports the latest ER materials along with their rheological understanding and provides a forward-looking summary of the potential future applications of ER technology.

Electrorheology of SI-ATRP-modified graphene oxide particles with poly(butyl methacrylate): effect of reduction and compatibility with silicone oil

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used to modify graphene oxide (GO) particles with poly(butyl methacrylate) (PBMA) chains. This procedure facilitated the single-step fabrication of a hybrid material with tailored conductivity for the preparation of a suspension in silicone oil with enhanced sedimentation stability and improved electrorheological (ER) activity. PBMA was characterized using various techniques, such as gel permeation chromatography (GPC) and ¹H NMR spectroscopy. Thermogravimetric analysis through on-line investigation of the Fourier transform infrared spectra, together with transmission electron microscopy, X-ray photoelectron microscopy, and atomic force microscopy, were successfully used to confirm GO surface modification. The ER performance was investigated using optical microscopy images and steady shear rheometry, and the mechanism of the internal chain-like structure formation was elucidated. The dielectric properties confirmed enhanced ER performance owing to an increase in relaxation strength to 1.36 and decrease in relaxation time to 5 × 10⁻³ s. The compatibility between GO and silicone oil was significantly influenced by covalently bonded PBMA polymer brushes on the GO surface, showing enhanced compatibility with silicone oil, which resulted in the considerably improved sedimentation stability. Furthermore, a controlled degree of reduction of the GO surface ensured that the suspension had improved ER properties.

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used to modify graphene oxide (GO) particles with poly(butyl methacrylate) (PBMA) chains.

Electrorheological Fluids with High Shear Stress Based on Wrinkly Tin Titanyl Oxalate

Electrorheological (ER) fluids are considered as a type of smart fluids because their rheological characteristics can be altered through an electric field. The discovery of giant ER effect revived the researchers' interest in the ER technological area. However, the poor stability including the insufficient dynamic shear stress, the large leakage current density, and the sedimentation tendency still hinders their practical applications. Herein, we report a facile and scalable coprecipitation method for synthesizing surfactant-free tin titanyl oxalate (TTO) particles with tremella-like wrinkly microstructure (W-TTO). The W-TTO-based ER fluids exhibit enhanced ER activity compared to that of the pristine TTO because of the improved wettability between W-TTO and the silicone oil. In addition, the static yield stress and leakage current of W-TTO ER fluids also show a fine time stability during the 30 day tests. More importantly, the dynamic shear stress of W-TTO ER fluids can remain stable throughout the shear rate range, which is valuable for their use in engineering applications. The results in this work provided a promising strategy to solving the long-standing problem of ER fluid stability. Moreover, this convenient route of synthesis may be considered a green approach for the mass production of giant ER materials.

Fabrication of graphene oxide polymer composite particles with grafted poly(amidoamine) dendrimers and their application in ion chromatography

Graphene oxide polymer composite particles with grafted PAMAM dendrimers and their application in ion chromatography.

The preparation and electrorheological behavior of bowl-like titanium oxide nanoparticles

Bowl-like titanium oxide nanoparticles were successfully prepared by a simple solvothermal method using absolute ethanol and isopropanol as the cosolvent. Ostwald ripening coupled with the inner-stress-induce effect were assumed to play an important role in the formation of this unique bowl-like morphology. The morphological evolution from solid nanosphere to bowl-like nanoparticle was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Besides, the structural characteristics of the as-synthesized TiO₂ nanoparticles were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA). Moreover, a rotational rheometer was operated to examine the electrorheological (ER) effect. Excellent ER properties were achieved when the TiO₂ particles were dispersed in silicone oil under an external electric field.

Enhanced Electrorheological Performance of Mixed Silica Nanomaterial Geometry

The mixed geometrical effect on the electrorheological (ER) activity of bimodal ER fluids was investigated by mixing SiO₂ spheres and rods of different dimensions. To gain an in-depth understanding of the mixed geometrical effect, 12 bimodal ER fluids were prepared from 4 sizes of SiO₂ spheres (50, 100, 150, and 350 nm) and 3 types of SiO₂ rods with different aspect ratios (L/D = 2, 3, and 5). Five concentrations of SiO₂ spheres and rods were created for each bimodal ER fluid, resulting in a total of 60 sets of comprehensive ER measurements. Some bimodal ER fluids exhibited enhanced ER performance, as high as 23.0%, compared to single SiO₂ rod-based ER fluids to reveal the mixed geometrical effect of bimodal ER fluids. This interesting experimental result is based on the structural reinforcement provided by spheres to fibrillated rod materials, demonstrating the mixed geometrical effect on ER activity.

Graphene oxide as an interface phase between polyetheretherketone and hydroxyapatite for tissue engineering scaffolds

The poor bonding strength between biopolymer and bioceramic has remained an unsolved issue. In this study, graphene oxide (GO) was introduced as an interface phase to improve the interfacial bonding between polyetheretherketone (PEEK) and hydroxyapatite (HAP) for tissue engineering scaffolds. On the one hand, the conjugated structure of GO could form strong π-π stacking interaction with the benzene rings in PEEK. On the other hand, GO with a negatively charge resulting from oxygen functional groups could adsorb the positively charged calcium atoms (C sites) of HAP. Consequently, the dispersibility and compatibility of HAP in the PEEK matrix increased with increasing GO content up to 1 wt%. At this time, the compressive strength and modulus of scaffolds increased by 79.45% and 42.07%, respectively. Furthermore, the PEEK-HAP with GO (PEEK-HAP/GO) scaffolds possessed the ability to induce formation of bone-like apatite. And they could support cellular adhesion, proliferation as well as osteogenic differentiation. More importantly, in vivo bone defect repair experiments showed that new bone formed throughout the scaffolds at 60 days after implantation. All these results suggested that the PEEK-HAP/GO scaffolds have a promising potential for bone tissue engineering application.

Hollow polymer particles: a review

Herein, the basic principles, such as the definitions, classifications, and properties, of hollow polymer particles (HPPs) are critically investigated.

Reduced graphene oxide wrapped core-shell metal nanowires as promising flexible transparent conductive electrodes with enhanced stability

Transparent conductive electrodes (TCEs) are widely used in a wide range of optical-electronic devices. Recently, metal nanowires (NWs), e.g. Ag and Cu, have drawn attention as promising flexible materials for TCEs. Although the study of core-shell metal NWs, and the encapsulation/overcoating of the surface of single-metal NWs have separately been an object of focus in the literature, herein for the first time we simultaneously applied both strategies in the fabrication of highly stable Ag-Cu NW-based TCEs by the utilization of Ag nanoparticles covered with reduced graphene oxide (rGO). The incorporation of Ag nanoparticles by galvanic displacement reaction was shown to significantly increase the long term stability of the electrode. Upon comparison with a CuNW reference, our novel rGO/Cu-AgNW-based TCEs unveiled remarkable opto-electrical properties, with a 3-fold sheet resistance decrease (from 29.8 Ω sq^-1 to 10.0 Ω sq^-1) and an impressive FOM value (139.4). No detrimental effect was noticed in the relatively high transmittance value (T = 77.6% at 550 nm) characteristic of CuNWs. In addition, our rGO/Cu-AgNW-based TCEs exhibited outstanding thermal stability up to 20 days at 80 °C in air, as well as improved mechanical flexibility. The superior performance herein reported compared with both CuNWs and AgNWs, and with a current conventional ITO reference, is believed to highlight the great potential of these novel materials as promising alternatives in optical-electronic devices.

Tunable electrorheological characteristics and mechanism of a series of graphene-like molybdenum disulfide coated core–shell structured polystyrene microspheres

Core–shell structured molybdenum disulfide (MoS₂) coated polystyrene (PS) microspheres are synthesized with the help of hexadecyl trimethyl ammonium bromide (CTAB) through negative–positive electrostatic attraction.

Three-dimensional graphene-based spheres and crumpled balls: micro- and nano-structures, synthesis strategies, properties and applications

3D spherical and crumpled-ball graphene-based architectures with diverse, fascinating properties and applications are reviewed for the first time.

The effect of fluorophore incorporation on fluorescence enhancement in colloidal photonic crystals

Diffusion-swelling dye incorporation method improves photonic structure-induced emission enhancement.

A morphology controllable synthesis of 3D graphene nanostructures and their energy storage applications

A morphology-controllable synthesis of 3D sulfonated graphene (SG) architectures were carried out.

Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics

The core-shell structured SiO₂@Ni-Al layered double hydroxide (LDH) composites were prepared via self-assembly of Ni-Al LDH on the surface of SiO₂ spheres. Only coating a layer of ultrathin Ni-Al LDH sheet, the resulting SiO₂@Ni-Al LDH composites exhibit significantly enhanced electrorheological (ER) characteristics compared to conventional bare SiO₂ spheres. The monodispersed SiO₂ spheres with average diameters of 260 nm were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), while the shell part, Ni-Al LDH sheet was prepared by the hydrothermal procedure. The morphology of the samples was investigated via scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure of the samples was characterized by X-ray diffraction (XRD). The species and distribution of elements in samples were confirmed by X-ray photoelectron spectroscopy (XPS), Energy dispersive analysis of X-ray (EDX) and elemental mapping in STEM. Subsequently, the ER characteristics of the composites dispersed in insulating oil were characterized by a rotational rheometer. The electric field-stimulated rheological performances (yield stress, viscosity, modulus, etc.) were observed under an external electric field, which is different from the Newtonian state in the free electric field.

Graphene oxide modified by betaine moieties for improvement of electrorheological performance

Novel graphene oxide bearing betaine moieties as sulfobetaine (GO-SB), carboxybetaine (GO-CB) and carboxybetaine ester (GO-CBE) moieties were prepared in two simple fabrication processes based on silanization and a thiol–ene click-reaction.

Hierarchical polystyrene@reduced graphene oxide–Pt core–shell microspheres for non-enzymatic detection of hydrogen peroxide

A non-enzymatic electrochemical sensor based on polystyrene@reduced graphene oxide (RGO)–Pt core–shell microspheres was developed for sensitive detection of hydrogen peroxide (H₂O₂).

Core-Shell Structured Electro- and Magneto-Responsive Materials: Fabrication and Characteristics

Core-shell structured electrorheological (ER) and magnetorheological (MR) particles have attracted increasing interest owing to their outstanding field-responsive properties, including morphology, chemical and dispersion stability, and rheological characteristics of shear stress and yield stress. This study covers recent progress in the preparation of core-shell structured materials as well as their critical characteristics and advantages. Broad emphasises from the synthetic strategy of various core-shell particles to their feature behaviours in the magnetic and electric fields have been elaborated.

Graphene oxide based smart fluids

Graphene oxide (GO), a graphene-related material containing oxygen-functional groups, has attracted considerable attention because of its strongly hydrophilic behavior and potential use in GO-hybrid composites. We put our focus on the fabrication and rheological characteristics of GO-based electrorheological and magnetorheological smart fluids under electric and magnetic fields, respectively in this Highlight. A brief perspective on the significant role of GO in tribology and the amphiphilic characteristics of Pickering emulsions are also included.

Chiral functionalization of graphene oxide by optically active helical-substituted polyacetylene chains and its application in enantioselective crystallization

This article reports an original, versatile strategy to chirally functionalize graphene oxide (GO) with optically active helical-substituted polyacetylene. GO was first converted into alkynyl-GO containing polymerizable -C≡C moieties, which took part in the polymerization of another chiral acetylenic monomer, yielding the expected GO hybrid covalently grafted with chiral helical polyacetylene chains. Transmission electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analyses verified the successful attachment of substituted polyacetylene chains on GO by covalent chemical bonding. Moreover, circular dichroism effects and UV-vis absorption demonstrated that the GO hybrid possessed fascinating optical activity. It also largely improved the dispersibility of GO in tetrahydrofuran. The GO-derived hybrid was further used as a chiral inducer toward enantioselective crystallization of alanine enantiomers. l-Alanine was preferably induced to crystallize, forming rodlike crystals.

Graphene size control via a mechanochemical method and electroresponsive properties

Highly dispersible graphene oxide (GO) sheets of uniform submicrometer size were successfully fabricated from pristine graphite using a simple mechanochemical process. The GO flake morphology was transformed into a spherical form, and the density was decreased slightly via the ball-milling process. Ball-milled GO can be used as an electrorheological (ER) material because of its small particle size, low conductivity, and outstanding dispersibility in silicone oil. We found that the 2-h ball-milled GO-based ER fluid had the best ER performance (shear stress of 78.5 Pa and 630% ER efficiency), which was double that of the nonmilled GO-based ER fluid. The response time to form a fibrillar structure along the applied electric field direction and the recovery time to the starting level decreased with increasing ball-milling time. Additionally, the retarded settling velocity of isolated GO sheets and the electrostatic repulsion between oxygen functional groups on the GO sheets combined to improve the antisedimentation property. The ability to control the size of graphene sheets is a great opportunity to advance graphene commercialization in a high-quality, scalable production setting.