Practical PBT/PC/GNP composites with anisotropic thermal conductivity

Most of the highly thermally conductive polymer-based composites currently face problems that must be solved before they can be directly used in industrial production. Herein, a practical polybutylene terephthalate (PBT)/polycarbonate (PC)/graphite nanoplatelet (GNP) thermally conductive composite with relative low filler content was prepared by a conventional melt-blending technique. GNPs selectively distributed and oriented in the PBT phase afford the composite a low percolation threshold and anisotropic thermal conductivity. Investigation of the influence of filler content on the final comprehensive performance showed that a prepared PBT/PC/GNP composite with 20 vol% GNPs exhibited superior performance in thermal conductivity, heat resistance, and mechanical properties. The in-plane and through-plane thermal conductivities of the composite were 5.82 W m⁻¹ K⁻¹ and 1.06 W m⁻¹ K⁻¹, respectively, which were increased by 2430% and 361% as compared to that of a neat PBT/PC blend. The Vicat softening temperature increased by 17.7 °C and reached 213.7 °C, while the mechanical properties also maintained a good application level.

The selective distribution of thermally conductive fillers in a co-continuous polymer blends provides an industrialized preparation method that takes into account both the properties and functions of thermally conductive composites.     

Boron carbide composites with highly aligned graphene nanoplatelets: light-weight and efficient electromagnetic interference shielding materials at high temperatures

B₄C-based ceramic composites containing 0–2 vol% highly aligned graphene nanoplatelets (GNPs) are fabricated. The electromagnetic interference (EMI) shielding properties of the obtained composites are investigated at X-band (8.2–12.4 GHz) frequency range from room-temperature up to 800 °C. All composites exhibit outstanding EMI shielding properties with satisfactory frequency- and thermal-stability. The shielding effectiveness (SE) of GNP/B₄C composites increases monotonically with increasing GNP loading. Superior room-temperature SE close to 40 dB is achieved with only 2 vol% GNPs and high SE around 35 dB still persists at 800 °C. Considering their relatively low density, GNP/B₄C composites possess a high specific shielding effectiveness (SSE) of 16 dB cm³ g⁻¹ which is among the highest values in reported ceramic-based shielding composites. Especially, the GNP/B₄C composite with 2 vol% GNPs exhibits the highest SSE/t (SSE divided by thickness) values at temperatures above 200 °C for all reported shielding composites, indicating that GNP/B₄C composites belong to the most promising high-temperature shielding composites. The excellent shielding properties of GNP/B₄C composites arise mainly from the high electrical conductivity, high dielectric loss and the multiple reflections by the highly aligned and large-sized GNP layers.

The incorporation of a small amount of highly aligned graphene nanoplatelets into boron carbide leads to light-weight and efficient high-temperature electromagnetic interference shielding composites.     

Electrodeposited nickel–graphene nanocomposite coating: effect of graphene nanoplatelet size on its microstructure and hardness

In this study, the effect of graphene nanoplatelet (GNP) size on the microstructure and hardness of the electrodeposited nickel–graphene nanocomposite coatings were investigated. GNPs with different sizes were prepared by using a high energy ball milling technique. The experimental result revealed the high energy ball milling technique could reduce the size, increase the surface area, and improve the dispersion ability of GNPs. The microstructure, hardness, and components of the nanocomposite coatings were greatly affected by GNP sizes. The highest microhardness was measured to be 273 HV for the nanocomposite coatings containing 5 h-milled GNPs, which is increased up to ∼47% compared to pristine Ni coating. The enhancement in the hardness is attributed to the uniform dispersion of the small GNP sizes inside the Ni matrix and the Ni grain size reduction when using milled GNPs.

The effect of graphene nanoplatelet size on the microstructure and hardness of electrodeposited nickel–graphene nanocomposite coatings was investigated.     

Surfactant-dependant thermally induced nonlinear optical properties of l-ascorbic acid-stabilized colloidal GNPs and GNP–PVP thin films

Gold nanoparticle (GNP) colloids stabilized with various concentrations of l-ascorbic acid were synthesized by the chemical reduction method and characterized by UV-Vis spectroscopy, XRD, FT-IR spectroscopy and TEM. XRD and TEM studies confirmed the reduction in particle size with the stabilizer concentration. UV-Vis spectra showed a blue shift in the LSPR peak. FT-IR peaks ascertained the strong encapsulation of GNPs with l-ascorbic acid functional groups. The nonlinear optical (NLO) properties of colloidal GNPs and GNP–PVP composite thin film were investigated using the Z-scan technique with CW laser excitation at 632.8 nm. The effects of stabilizer concentrations on nonlinear refractive index (n₂), nonlinear absorption coefficient (β) and third-order susceptibility (χ⁽³⁾) of colloidal GNPs and GNP–PVP composite thin films were investigated. The values of the NLO parameters for the thin films were as large as n₂ = 10⁻⁵ cm² W⁻¹, β = 10⁻⁵ cm W⁻¹ and χ⁽³⁾_eff = 10⁻⁵ esu. For colloidal GNPs, these parameters were n₂ = 10⁻⁶ cm² W⁻¹, β = 10⁻⁶ cm W⁻¹ and χ⁽³⁾_eff = 10⁻⁷ esu. In both these cases, the NLO parameter values were found to decrease as the stabilizer concentration increased from 1 to 5 mM. The considerable enhancement in the NLO parameters may be attributed to the thermal lensing effect originating from the thermo-optic phenomenon. From the results, the influence of the concentration of the stabilizer on the NLO properties is obvious.

Gold nanoparticle (GNP) colloids stabilized with various concentrations of l-ascorbic acid were synthesized by the chemical reduction method and characterized by UV-Vis spectroscopy, XRD, FT-IR spectroscopy and TEM.     

Graphene nanoplatelets-sericin surface-modified Gum alloy for improved biological response

In this study a “Gum Metal” titanium-based alloy, Ti-31.7Nb-6.21Zr-1.4Fe-0.16O, was synthesized by melting and characterized in order to evaluate its potential for biomedical applications. The results showed that the newly developed alloy presents a very high strength, high plasticity and a low Young''s modulus relative to titanium alloys currently used in medicine. For further bone implant applications, the newly synthesized alloy was surface modified with graphene nanoplatelets (GNP), sericin (SS) and graphene nanoplatelets/sericine (GNP–SS) composite films via Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The characterization of each specimen was monitored by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) measurements, and Fourier Transform Infrared Spectroscopy (FTIR). The materials'' surface analyses suggested the successful coating of GNP, SS and GNP–SS onto the alloy surface. Additionally, the activities of pre-osteoblasts such as cell adhesion, cytoskeleton organization, cell proliferation and differentiation potentials exhibited on these substrates were investigated. Results showed that the GNP–SS-coated substrate significantly enhanced the growth and osteogenic differentiation of MC3T3-E1 cells when compared to bare and GNP-coated alloy. Collectively, the results show that GNP–SS surface-modified Gum alloy can modulate the bioactivity of the pre-osteoblasts holding promise for improved biological response in vivo.

GNP–SS functionalized Gum alloy exhibits superior bioactivity in inducing in vitro osteogenesis.     

Enhanced thermal conductivity and mechanical properties of a GNP reinforced Si3N4 composite

Graphene nanocomposites can significantly enhance the thermal conductivity and mechanical properties of ceramics at relatively low nano-filler addition. Herein, graphene nano-platelet reinforced Si₃N₄ (GNP/Si₃N₄) composites were prepared by hot press (HP) sintering using fluoride (AlF₃, MgF₂) sintering-additives. The microstructural properties revealed the enhanced crystallization degree and density of the GNP/Si₃N₄ composites with different concentrations of graphene nano-platelets (GNPs). These properties help to achieve a significantly improved thermal conductivity (from 82.42 to 137.47 W m⁻¹ K⁻¹) of the GNP/Si₃N₄ composites. The morphology of the composites shows a uniform distribution of GNP, whereas overlapping of GNPs (2 to 4 platelets) at the grain boundaries of Si₃N₄ was observed. The fracture toughness and Vickers hardness of the composites also increased with the increasing content of GNP. The toughening mechanism was similar in all composites with GNP addition in respect of pull out, crack deflection, crack branching and crack bridging.

Graphene nanocomposites can significantly enhance the thermal conductivity and mechanical properties of ceramics at relatively low nano-filler addition.     

Preparation of self-healing polyurethane/functionalized graphene nanocomposites as electro-conductive one part adhesives

We report the synthesis and investigation of the electrical conductivity and self-healing properties of moisture curable polyurethane (PU) adhesives filled with functionalized graphene nanosheets and isophorone diisocyanate (IPDI) loaded poly(methyl methacrylate) (PMMA) nanocapsules. For this purpose, chemically functionalized graphene was prepared by covalently grafting 4-(4,5-diphenyl-1H-imidazol-2-yl)phenol (DIP) on the surface of graphene oxide and synthesized PMMA nanocapsules were loaded with IPDI. Both nanofillers were then dispersed in a polyurethane matrix and the effects on the adhesion properties of the adhesives in aluminum–aluminum metal joints were studied. The results showed that by surface modification and better exfoliation of graphene nanosheets, the electrical conductivity was increased from 2.2 × 10⁻⁹ S m⁻¹ to 4.1 S m⁻¹ for pure PU and 10 wt% graphene based nanofiller loaded PU, respectively. The thermal stability, electrical conductivity, shear strength and self-healing process of the ECAs were also studied. The results provide evidence that the prepared adhesives have the potential for applications in electronic device packaging.

One part moisture curable adhesives based on polyurethane/functionalized graphene nanocomposites were synthesized and showed good electrical conductivity, thermal stability, shear strength and self-healing properties.     

Engineered nano-sphere array of gold-DNA core–shells and junctions as opto-plasmonic sensors for biodetection

In this paper, we design opto-plasmonic sensors by the engineered arrangement of gold-nanospheres. We use DNA-gold nanoparticle (GNP) core–shells and DNA rods as junctions between GNPs with a fishnet ground layer for controlling and improving the absorbance and reflection in the range of 100–300 THz. Based on available data, we check the effects of healthy and cancerous cells on the reflection parameter. Here, we demonstrate how the DNA junctions and distance between the nanospheres can be considered to modify the reflection. These structures can be utilized as opto-plasmonic sensors with high sensitivity to distinguish materials in terms of refractive indices. We can use an array of these sensors for both spectroscopy and optical imaging on a real scale. The proposed structures with different topologies are analyzed and their figure of merits (FOM) and sensitivities are obtained. The structure based on the DNA rods as junctions between GNPs shows the best FOM value of 340 RIU⁻¹ and the core–shell heptamer structure has the best sensitivity of about 1287 nm RIU⁻¹.

Several engineered optoplasmonic structures including DNA rods as junctions between GNPs for controlling and improving the absorbance were proposed.     

Enhanced thermal conductivity of nanocomposites with MOF-derived encapsulated magnetic oriented carbon nanotube-grafted graphene polyhedra

It remains a challenge to develop highly polymer-based nanocomposite thermal interface materials, which can effectively remove heat developed during the miniaturization of electronic instruments. It has been reported that a large number of graphene-based nanocomposites exhibit excellent performance. However, it is still an issue to construct thermal conductive pathways by orientation arrangements with a low filler volume fraction. Herein, a high-thermal conductivity filler of magnetic carbon nanotube-grafted graphene polyhedra (Co@Co₃O₄-G) was exploited via the annealing of metal–organic frameworks (ZIF-67). Co@Co₃O₄-G can improve the thermal conductivity of nanocomposites obviously by forming oriented pathways for phonon transport in an external magnetic field. Therefore, the resulting nanocomposite displayed a high thermal conductivity of 2.11 W m⁻¹ K⁻¹ for only 8.7 vol%, which is 10 times higher than that of the pure epoxy resin. Core-shell magnetic cobalt oxide (Co@Co₃O₄) was encapsulated in situ in the nanoarchitecture to avoid falling off. Moreover, the equilibrium molecular dynamics (EMD) simulation verifies that Co@Co₃O₄-G had high thermal conductivity to effectively improve the heat dissipation of nanocomposites. This strategy provides an approach for developing high-performance thermal management materials and opens up the possibility for the pioneering applications of encapsulated magnetic-oriented thermal conductive fillers.

A high-thermal conductivity filler of magnetic carbon nanotube-grafted graphene polyhedra is exploited via annealing of a metal–organic framework (ZIF-67).     

Enhanced electrical and thermal properties of semi-conductive PANI-CNCs with surface modified CNCs

Cellulose nanocrystals (CNCs) are the most commonly used natural polymers for biomaterial synthesis. However, their low dispersibility, conductivity, and poor compatibility with the hydrophobic matrix hinder their potential applications. Therefore, we grafted sulfate half-ester and carboxylic functional groups onto CNC surfaces (S-CNC and C-CNC) to overcome these shortcomings. The effect of the dopants, surfactant ratios, and properties of CNCs on the thermal stability, conductivity, and surface morphology of polyaniline (PANI)-doped CNC nanocomposites were investigated through emulsion and in situ polymerization. The higher electrical conductivity and well-dispersed morphology of SCNC–PANI₃₀ (1.1 × 10⁻² S cm⁻¹) but lower thermal stability than that of CCNC–PANI₃₀ (T₀: 189 °C) nanocomposites are highly related to dispersibility of S-CNCs. However, after 4-dodecylbenzenesulfonic acid (DBSA) was added, the conductivity and thermal stability of SCNC/PANI increased up to 2.5 × 10⁻¹ S cm⁻¹ and 192 °C with almost no particle aggregation because of the increase in charge dispersion. The proposed biodegradable, renewable, and surface-modified S-CNC and C-CNC can be used in high-thermal-stability applications such as food packaging, optical films, reinforcement fillers, flexible semiconductors, and electromagnetic materials.

Biodegradable surface-modified CNCs were synthesized found high dispersibility and flexibility. Polyaniline-doped CNCs nanocomposites were exhibited high conductivity and thermal stability that may be promising for flexible semiconductors.     

Integrated optical and electrochemical detection of Cu2+ ions in water using a sandwich amino acid–gold nanoparticle-based nano-biosensor consisting of a transparent-conductive platform

In this paper, an optical-electrochemical nano-biosensor was introduced for measuring Cu²⁺ ion concentrations in water. A multi-step procedure was used to fabricate the transparent-conductive biosensor platform consisting of an l-cysteine–gold nanoparticle-based sandwich structure. First, colloidal gold nanoparticles (GNPs) were synthesized according to the Turkevich–Frens method with some modifications and then functionalized with l-cysteine molecules (GNP/l-cys). Then, cyclic voltammetry was preformed in buffered solutions containing HAuCl₄·3H₂O for gold nanoparticle electrodeposition on cleaned ITO glasses. The GNP-electrodeposited ITO glasses (ITO/GNPs) were thermally treated in air atmosphere for 1 hour at a temperature of 300 °C. Following the procedure, the gold nanoparticles on ITO/GNPs substrates were functionalized with l-cysteine to prepare ITO/GNPs/l-cys substrates. Finally, the sandwich-type substrates of ITO/GNPs/l-cys⋯Cu²⁺⋯l-cys/GNPs were fabricated by accumulation of Cu²⁺ ions using an open circuit technique performed in copper ion buffer solutions in the presence of previously produced colloidal GNP/l-cys nanoparticles. The effective parameters including GNP/l-cys solution volume, pre-concentration pH and pre-concentration time on the LSPR and SWV responses were investigated and optimized. The fabricated transparent-conductive platforms were successfully assessed as a nano-biosensor for detection of copper ions using two different methods of square wave voltammetry (SWV) and localized surface plasmon resonance (LSPR). As a result, the proposed biosensor showed a high sensitivity, selectivity and a wide detectable concentration range to copper ions. The total linear range and the limit of detection (LOD) of the nano-biosensor were 10–100 000 nM (0.6–6354.6 ppb) and below 5 nM (0.3 ppb), respectively. The results demonstrated the potential of combining two different optical and electrochemical methods for quantitation of the single analyte on the same biosensor platform and obtaining richer data. Also, these results indicated that the developed LSPR-SWV biosensor was superior to many other copper biosensors presented in the literature in terms of linear range and LOD. The developed nano-biosensor was successfully applied in the determination of trace Cu²⁺ concentration in actual tap water samples.

The transparent-conductive platforms of ITO/GNPs/l-cys⋯Cu²⁺⋯l-cys/GNPs were fabricated for quantitation of Cu²⁺ ions in water samples using combined LSPR and SWV methods.     

Ionic cellulose-stabilized gold nanoparticles and their application in the catalytic reduction of 4-nitrophenol

A novel strategy for the synthesis of highly stable gold nanoparticles (GNPs) was designed by reducing HAuCl₄ with NaBH₄ in an aqueous solution of water-soluble ionic cellulose composed of dimethylimidazolium cations and phosphite-bound cellulose anions. NMR and UV-Vis analysis along with the measurement of the zeta potential suggest that the exceptionally high stability of GNPs originates from the strong interaction of GNPs with the phosphite groups of the ionic cellulose. The thus prepared GNPs exhibit excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol, a model hydrogenation reaction.

Gold nanoparticles (GNP) were highly stabilized by water soluble ionic cellulose by the strong interaction of GNP with the phosphite groups and showed extremely high catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol.     

The chemical functionalization of graphene nanoplatelets through solvent-free reaction

Graphene nanoplatelets (GNPs) were functionalized through 1,3-dipolar cycloaddition of azomethine ylide using a solvent-free approach and under different reaction conditions. The yield and the functionality of the carboxyl-terminated pyrrolidine ring attached on the surface of GNPs could be affected by varying the reaction temperature as well as the reactant to GNP weight ratio. The functionalized GNPs were characterized extensively using a range of spectroscopic and microscopy techniques.

Carboxyl-terminated pyrrolidine functionalized graphene nanoplatelets through a solvent-free reaction.     

Thermal conductivity and molecular heat transport of nanofluids

Fluid media such as water and ethylene glycol are usually quite poor conductors of heat. Nanoparticles can improve the thermal properties of fluids in a remarkable manner. Despite a plethora of experimental and theoretical studies, the underlying physics of heat transport in nanofluids is not yet well understood. Furthermore, the link between nanoscale energy transport and bulk properties of nanofluids is not fully established. This paper presents a thermal conductivity model, encapsulating solid–liquid interfacial thermal resistance, particle shape factor and the variation of thermal conductivity across a physisorbed fluidic layer on a nanoparticle surface. The developed model for thermal conductivity integrates the interfacial Kapitza resistance, the characteristics of a nanolayer, convective diffusion and surface energy with capillary condensation. In addition, the thickness of the nanolayer is predicted using the Brunauer–Emmett–Teller (BET) isotherms and micro/nano-menisci generated pressures of condensation. Such a comprehensive model for thermal conductivity of nanoparticles and systematic study has not hitherto been reported in the literature. The thermal conductivity model is evaluated using experimental data available in open literature.

The developed model for thermal conductivity of nanofluids integrates the interfacial Kapitza resistance, the characteristics of the nanolayer, convective diffusion and surface energy with capillary condensation.     

Nanofiller-conjugated percolating conductive network modified polymerization reaction characteristics of aromatic thermosetting copolyester resin

Deliberately controlled interfacial interactions between incorporated nanofiller particles and host polymer backbone chains constitute a critical element in the realm of polymer nanocomposites with tailorable multifunctional properties. We demonstrate the physicochemical effects induced by graphene nanoplatelets (GNP) of different sizes on the condensation polymerization reaction of aromatic thermosetting copolyester (ATSP) through the formation of electrically conductive percolating networks as enabled by interfacial interactions. Carboxylic acid and acetoxy-capped precursor oligomers of ATSP are solid-state mixed with chemically pristine GNP particles at various loading levels. Upon in situ endothermic condensation polymerization reaction, crosslinked backbone of the ATSP foam matrix is formed while the carbonaceous nanofillers are incorporated into the polymer network via covalent conjugation with functional end-groups of the oligomers. The controlled GNP size promotes different electrical percolation thresholds and ultimate electrical conductivities. Microstructural analysis demonstrates GNP distributions in the matrix as well as morphological modifications induced by the formation of conductive percolating GNP networks. Cure characteristics reveal the thermochemical changes prompted in the polymerization processes for GNP content above the requirement for percolation formation. Chemical spectroscopy of the ATSP nanocomposite morphology exhibits the formation of a robust interfacial coupling mechanism between the GNPs and ATSP backbone. The findings here may guide the developmental efforts of nanocomposites through better identifying roles of the morphology and content of nanofillers in polymerization processes.

Physicochemical effects induced by graphene nanoplatelets on the in situ polycondensation reaction of aromatic thermosetting copolyester through the formation of conductive percolating network assembled via interfacial interactions.     

Tunable electrical properties of carbon dot doped photo-responsive azobenzene–clay nanocomposites

The development of photo-responsive nanocomposite materials is important in the fabrication of optoelectronic devices. In this work, we fabricated a carbon dot doped azobenzene–clay nanocomposite which possesses different ac conductivity with and without UV treatment. At first, azobenzene nanoclusters were synthesised and then successfully used to make an azobenzene–clay nanocomposite. It was observed that there is a small change in the ac conductivity of the azobenzene–clay nanocomposite with and without UV treatment. However, this change in ac photoconductivity can be enhanced in the azobenzene–clay nanocomposite by doping with electron-rich cysteine and methionine carbon dots. Hence, ac conductivity properties of the carbon-doped azobenzene–clay nanocomposite can be tuned using UV light. Impedance measurements were determined using Electrochemical Impedance Spectroscopy. Mechanistic insight into the phenomenon is also discussed in the paper. Thus fabrication of tunable carbon dot doped photo-responsive azobenzene–clay nanocomposites will lead to the use of carbon dot doped azobenzene–clay nanocomposites in photo-switchable optoelectronic devices.

We demonstrate successful fabrication of an azobenzene–clay nanocomposite doped with electron-rich cysteine and methionine carbon dots with photo-switchable ac conductivity.     

Effect of benzoic acid surface modified alumina nanoparticles on the mechanical properties and crystallization behavior of isotactic polypropylene nanocomposites

The effect of benzoic acid (BA) surface modified alumina (Al₂O₃) nanoparticles (NPs) on the mechanical properties and crystallization behavior of isotactic polypropylene (iPP) nanocomposites was studied. Characterization of the modified Al₂O₃ NPs (BA-Al₂O₃) by FTIR and XRD analyses confirmed that benzoic acid molecules chemisorb on the surface of the NPs, forming benzene groups-rich microstructures. A considerable increase in the tensile strength, flexural modulus, and toughness was observed for the nanocomposites with only 0.2 wt% BA-Al₂O₃. Enhanced interfacial adhesion with the matrix was achieved, which enabled effective reinforcement of the nanocomposites. The higher crystallization temperature along with shorter crystallization halftime indicated the higher nucleation activity of BA-Al₂O₃. Furthermore, the interchain conformational ordering of iPP was significantly accelerated in the presence of the BA-Al₂O₃ NPs. The CH–π interaction between the polymer and BA-Al₂O₃ NPs was considered to facilitate the attachment of the iPP chains and stimulate conformational ordering, crystallization, as well as mechanical properties of nanocomposites.

The CH–π interactions between polypropylene and functionalized alumina (BA-Al₂O₃) nanoparticles improve the mechanical performance and conformational ordering of nanocomposites.     

One-pot synthesis of Ag–Cu–Cu2O/C nanocomposites derived from a metal–organic framework as a photocatalyst for borylation of aryl halide

Mixed metal–metal oxide/C (Ag–Cu–Cu₂O/C) nanocomposites were synthesized by the heat treatment of a metal–organic framework under a N₂ flow using the one-pot synthesis method. The as-prepared nanocomposites were characterized using a range of techniques, such as TEM, elemental mapping, XRD, N₂ sorption, UV-Vis DRS, and XPS. The nanoparticles were successfully formed with high dispersion in porous carbon materials and high crystallinity based on the analysis results. The Ag–Cu–Cu₂O/C nanocomposites (35 nm) showed high photocatalytic activity and good recyclability toward the borylation of aryl halides under a xenon arc lamp. This result can enhance the interest in photocatalysis for various applications, particularly in organic reactions, using a simple and efficient synthesis method.

Ag–Cu–Cu₂O/C nanocomposites derived from metal–organic framework through one-pot thermal reduction method were synthesized. The material exhibits high catalytic activity in the borylation of aryl halide under xenon lamp condition across 7 cycles, with no yield decrease.     

Comparative study of antidiabetic,bactericidal, and antitumor activities of MEL@AgNPs,MEL@ZnONPs,and Ag–ZnO/MEL/GA nanocomposites prepared by using MEL and gum arabic

In this study, a variety of nanocomposites, namely, MEL@AgNPs, MEL@ZnONPs, and Ag–ZnO/MEL/GA were biosynthesized using MEL and gum arabic to serve in biomedical applications. The synthesized nanocomposites were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and FTIR spectroscopy. The physicochemical properties and biomedical activities of the synthesized nanocomposites were investigated. The Ag–ZnO/MEL/GA nanocomposites showed greater antidiabetic activity against α-amylase and α-glucosidase, and higher antibacterial activity compared to MEL@AgNPs and MEL@ZnONPs. Furthermore, HepG2 cells were exposed to MEL@AgNPs, MEL@ZnONPs, and Ag–ZnO/MEL/GA nanocomposites for 24 h and their IC₅₀ values were 63.25, 26.91 and 28.97 μg mL⁻¹ (P < 0.05), respectively. According to this comparative study, it is apparent that the Ag–ZnO/MEL/GA nanocomposites have a great potential to serve as antitumor agents against HepG2, and antidiabetic and antibacterial agents.

MEL@AgNPs, MEL@ZnONPs, and Ag–ZnO/MEL/GA nanocomposites were successfully prepared by using mannosylerythritol lipids (MEL) and gum arabic.     

Enhanced mechanical,thermal, and UV-shielding properties of poly(vinyl alcohol)/metal–organic framework nanocomposites

Metal–organic framework (HKUST-1) nanoparticles were successfully synthesized, and poly(vinyl alcohol) (PVA)/HKUST-1 nanocomposite films were fabricated by a simple solution casting method. Our results showed that the addition of HKUST-1 caused a remarkable enhancement in both thermal stability and mechanical properties of the PVA nanocomposites, due to the homogeneous distribution of HKUST-1 and the strong interfacial interactions between PVA and HKUST-1. With incorporation of 2 wt% HKUST-1, the degradation temperature of the nanocomposites was about 33 °C higher than that of pure PVA. At the same time, the Young''s modulus and tensile strength of the nanocomposites was approximately 137% and 32% higher than those of pure PVA, respectively. Moreover, the PVA/HKUST-1 nanocomposites also showed strikingly enhanced UV-shielding ability as well as satisfactory visible light transmittance, which revealed that HKUST-1 nanoparticles could act as a good UV absorber in nanocomposites. This work provides a novel and simple method for producing UV-shielding materials with simultaneously enhanced thermal and mechanical properties, which have potential applications in UV protection areas.

PVA/HKUST-1 nanocomposites prepared by a simple solution casting method displayed significantly enhanced thermal stability, mechanical and UV-shielding properties.