Transparent Dispersions of Monodispersed ZnO Nanoparticles with Ultrahigh Content and Stability for Polymer Nanocomposite Film with Excellent Optical Properties

UV/blue-light-blocking polylactide films derived from bio-sources for food packaging application

Transparent biodegradable packaging materials capable of blocking the broad-spectrum of UV and blue light (200-500 nm) are crucial for packaging of light-sensitive food. This study offers a fully bio-based solution based on polylactide and natural light absorbers, aloe-emodin (AE) and riboflavin (RF), whose combined UV-vis absorption spectrum covers all the light between 200 and 500 nm. AE and RF were bonded to polylactide chains by serving as initiators for the ring-opening polymerization of lactide, resulting in the synthesis of light-blocking polylactides, PLA-E and PLA-R. To fabricate UV and blue light-blocking polylactide film (PLA/EmRn), PLA-E and PLA-R were blended with commercial polylactide. For the PLA/EmRn film containing only 0.87 mass% AE and RF group introduced by PLA-E and PLA-R, the transmittance against the UV-B, UV-A and blue light was only 38.8 %, 27.7 % and 25.5 %, respectively. Meanwhile, the film maintains high transparency (91.4 %) and good tensile strength above 59 MPa. Furthermore, the PLA/EmRn film exhibits an extended capacity for light-blocking, which may help reduce the photodegradation of the photosensitive nutrient riboflavin. Its protective performance surpasses both the polylactide film and commercially available PET packaging films. This study offers an eco-friendly strategy for developing UV/blue light-blocking food packaging based on all renewable resources.

Enhancing flame retardancy and heat insulation performances of polyamide 66 composite film by adding CNC/Al2O3 nanohybrids

Polyamide 66 (PA66) has garnered significant attention due to its exceptional properties; unfortunately, its flammability is challenging. Adding flame retardants (FRs) is a primary approach to enhance PA66 flame retardancy. This study developed a highly flame-retardant PA66 composite film by adding corn-like functional nanohybrids (CNC/Al2O3). Interestingly, CNC/Al2O3 nanohybrids not only formed hydrogen bond interactions with PA66 but also improved crystallization properties as heterogeneous nucleating agents, resulting in the excellent mechanical properties of PA66 composite film. Remarkably, the incorporation of 3 wt% CNC/Al2O3 nanohybrids into PA66 matrix contributed to increasing the LOI to 28.5 %. The pHRR, THR, and TSR were reduced obviously by 55.7 %, 15.3 %, and 65.2 %, respectively. The excellent flame retardancy of PA66 composite film was attributed to the forming of a compact carbon layer catalyzed by the CNC/Al2O3 nanohybrids. Besides, the homogeneous distribution of CNC/Al2O3 nanohybrids endowed the composite film with excellent heat insulation, and the heat insulation rate was up to 31.9 %. Thus, such PA66 composite films with excellent flame retardancy, heat insulation, and mechanical properties could meet the broader application requirements.

High-Performance Self-Powered Quantum Dot Infrared Photodetector with Azide Ion Solution Treated Electron Transport Layer

The demand for self-powered photodetectors (PDs) capable of NIR detection without external power is growing with the advancement of NIR technologies such as LIDAR and object recognition. Lead sulfide quantum dot-based photodetectors (PbS QPDs) excel in NIR detection; however, their self-powered operation is hindered by carrier traps induced by surface defects and unfavorable band alignment in the zinc oxide nanoparticle (ZnO NP) electron-transport layer (ETL). In this study, an effective azide-ion (N3 -) treatment is introduced on a ZnO NP ETL to reduce the number of traps and improve the band alignment in a PbS QPD. The ZnO NP ETL treated with azide ions exhibited notable improvements in carrier lifetime and mobility as well as an enhanced internal electric field within the thin-film heterojunction of the ZnO NPs and PbS QDs. The azide-ion-treated PbS QPD demonstrated a increase in short-circuit current density upon NIR illumination, marking a responsivity of 0.45 A W-1, specific detectivity of 4 × 1011 Jones at 950 nm, response time of 8.2 µs, and linear dynamic range of 112 dB.

A Universal Approach for Controllable Synthesis of Homogeneously Alloyed PtM Nanoflowers toward Enhanced Methanol Oxidation

Platinum (Pt)-based alloys have received considerable attention due to their compositional variability and unique electrochemical properties. However, homogeneous element distribution at the nanoscale, which is beneficial to various electrocatalytic reactions, is still a great challenge. Herein, a universal approach is proposed to synthesize homogeneously alloyed and size-tunable Pt-based nanoflowers utilizing high gravity technology. Owing to the significant intensification of micro-mixing and mass transfer in unique high gravity shearing surroundings, five typical binary/ternary Pt-based nanoflowers are instantaneously achieved at room temperature. As a proof-of-concept, as-synthesized Platinum-Silver nanoflowers (PtAg NFs) demonstrate excellent catalytic performance and anti-CO poisoning ability for anodic methanol oxidation reaction with high mass activity of 1830 mA mgPt -1 , 3.5 and 3.2 times higher than those of conventional beaker products and commercial Pt/C, respectively. The experiment in combination with theory calculations suggest that the enhanced performance is due to additional electronic transmission and optimized d-band center of Pt caused by high alloying degree.

A novel theoretical method to determine the effective optical properties of high refractive index nanocomposites

The continuous development of advanced optical devices towards high performance, miniaturization and integration has led to an increasing demand for high refractive index optical materials. Nanocomposites - made from high refractive index inorganic nanoparticles and good processability polymers - combine the advantages of both materials to create a synergistic effect. However, the diversity and complexity of the composites make laboratory preparation less efficient. Therefore, to prepare composites that meet the refractive index requirements, it is essential to predict the effective optical properties at different wavelengths. This study proposes a finite element parametric retrieval (FEPR) method to calculate the effective complex refractive index of nanocomposites (meff). The effects of the ratio of film thickness to particle diameter, particle arrangement, particle volume fraction (fv) and particle diameter (d) on meff are considered. The results demonstrate that changing the spatial arrangement, volume fraction and diameter of the particles can cause changes in the scattering effect of particles or the interaction between the electromagnetic waves and the particles, resulting in changes in the meff. Compared with effective medium theory (EMT), the FEPR method can be used to characterise the meff values in complex cases through finite element parametric modelling. The FEPR method is an efficient and accurate method for predicting the effective optical properties of nanocomposites, and can also be applied to the design and development of materials to discover the factors influencing the properties and variation patterns from large amounts of data, and to obtain predictive models that can guide the design of new materials.

A modular design approach to polymer-coated ZnO nanocrystals

Hybrid materials based on inorganic nanocrystals with organic polymers feature peculiar and fascinating properties and various applications. However, there is still a need for simple synthesis procedures that provide precise control over the polymer/nanocrystal microstructure of these materials. Herein, a novel organometallic approach to polymer-coated ZnO nanocrystals was developed. The presented method merges the initial ring-opening polymerization of ϵ-caprolactone mediated by an organozinc alkoxide initiator and an air-promoted transformation of the resulting macromolecular organozinc species. This one-pot procedure results in quantum-sized ZnO crystals with a core diameter of ca 3 nm coated by poly(ϵ-caprolactone) covalently bonded to the surface. Overall, the ability to create well-defined hybrid composites should provide a unique ability to access various nanosystems.

Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior

Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO₂) and vinyl-functionalized (V-SiO₂) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO₂ composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO₂ induced no significant changes in gel fraction and both V-SiO₂ and MA-SiO₂ nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO₂ composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO₂ composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO₂ and a monomodal size distribution for MA-SiO₂. Although aggregates were observed for both nanoparticle surface treatments, V-SiO₂ dispersion was poor while MA-SiO₂ were generally well-dispersed. These findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.

Chiral poly(amide-imide)/ZnS nanocomposite as a new adsorbent for simultaneous removal of cationic dyes from aqueous solution

A new adsorbent, poly(amide-imide)/zinc sulfide nanocomposite (PAI/ZnS NC), was fabricated and identified by Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy. Then, the obtained NC was applied for the simultaneous removal of auramine O (AO) and rhodamine B (RB) dyes from aqueous solution via the interactions of hydrogen bonding, π– π stacking, and Lewis acid–base interaction. The effects of operational variables including pH, PAI/ZnS NC mass, AO and RB concentration, and sonication time on removal efficiency were examined and optimized values were found to be 8.0, 16 mg, 11 mg L−1, and 6 min, respectively. The adsorption capacities of PAI/ZnS NC for the removal of AO and RB dyes were found to be 70.92 and 91.74 mg g−1, respectively. Ultraviolet–visible spectrophotometer was used to determine the amount of residual dye in solution. Fitting the experimental equilibrium data to isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich reveals the suitability of the Langmuir model with high correlation coefficients ( R2 = 0.998 for AO and R2 = 0.999 for RB). Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models applicability was tested and the pseudo-second-order equation controls the kinetics of the adsorption process. Furthermore, this study establishes that PAI/ZnS NC can be successfully applied as a low-cost adsorbent and conserve its high efficiency after nine cycles for the removal of AO and RB dyes.

Controlled dispersion of ZnO nanoparticles produced by basic precipitation in solvothermal processes

Zinc oxide nanoparticles were successfully synthesized under precipitation processes, using ZnSO4·7H2O as a Zn2+ precursor and K2CO3 used as a basic source, and hydrozincite was obtained as an intermediary, which was treated under two procedures; first procedure involved multiple stages to get final precipitated with NaOH, and in the second procedure the hydrozincite was straightforwardly dried at 220 °C. By both processes ZnO structures were obtained, which were turned into nanoparticles by a solvothermal treatment, for four hours in ethylene glycol at 200 °C. The final products for the first procedure was conglomerate of spherical nanoparticles with sizes ranged between 5-10 nm and dispersed ellipsoidal nanoparticles for the second procedure. Apart off the two procedures mentioned above, another synthesis was carried out with the same Zn2+ precursor but now using NaOH, and the solvothermal treatment produced ZnO mixed micro-structures which under ultrasonic cavitation disaggregated on mesoporous ZnO nanoplates of hexagonal shapes with nanopore sizes of approximately 0.35 nm. All ZnOs synthesized were structurally characterized with XRD, TEM and FT-IR techniques, and electronically with UV-Vis absorption and diffuse reflectance spectroscopies.

Excellent UV Resistance of Polylactide by Interfacial Stereocomplexation with Double-Shell-Structured TiO2 Nanohybrids

The durable application of polylactide (PLA) under atmospheric conditions is restricted by its poor ultraviolet (UV) stability. To improve the UV stability of polymers, titanium dioxide (TiO₂) is often used as a UV light capture agent. However, TiO₂ is also a photocatalytic agent, with detrimental effects on the polymer properties. To overcome these two conflicting issues, we used the following approach. TiO₂ nanoparticles were first coated with silicon dioxide (SiO₂) (with a SiO₂ shell content of 5.3 wt %). Subsequently, poly(d-lactide) (PDLA) was grafted onto TiO₂@SiO₂ nanoparticles, approximately 20 wt %, via a ring-opening polymerization of d-lactide to obtain well-designed double-shell TiO₂@SiO₂-g-PDLA nanohybrids. These double-shell nanoparticles could be well dispersed in a poly(l-lactide) (PLLA) matrix making use of the stereocomplexation between the two enantiomers. In our concept, the inner SiO₂ shell on the TiO₂ nanoparticles prevents the direct contact between TiO₂ and the PLLA matrix and hence considerably restricts the detrimental photocatalytic effect of TiO₂ on PLLA degradation. Additionally, the outer PDLA shell facilitates an improved dispersion of these nanohybrid particles by interfacial stereocomplexation with its enantiomer PLLA. As a consequence, the PLLA/TiO₂@SiO₂-g-PDLA nanocomposites simultaneously possess excellent UV-shielding property, high(er) tensile strength (>60 MPa), and superior UV resistance, for example, the mechanical properties remain at a level of >90% after 72 h of UV irradiation. In our view, this work provides a novel strategy to make advanced PLA nanocomposites with improved mechanical properties and excellent UV resistance, which enables potential application of PLA in more critical areas such as in durable packaging and fiber/textile applications.

Transparent Wood Composites Fabricated by Impregnation of Epoxy Resin and W-Doped VO2 Nanoparticles for Application in Energy-Saving Windows

Two types of transparent wood composites with anisotropic structure for energy-saving windows were successfully fabricated by infiltration of epoxy resin dispersion containing tungsten-doped vanadium dioxide nanoparticles (W-doped VO₂ NPs) into the delignified wood template and subsequent polymerization. The well integration of the epoxy resin, W-doped VO₂ NPs, and the pore-structured wood endowed the anisotropic composites with high visible transmittance (68.2% for the composite prepared from longitudinally cut trees (L-composite), 73.3% for the composite prepared from radically cut trees (R-composite)), obviously different mechanical performance (fracture stress of 74.57 MPa (L-composite) and 56.14 MPa (R-composite) and modulus of 1.47 GPa (L-composite) and 1.23 GPa (R-composite)), and low thermal conductivity (0.20 W·m^-1 K^-1 (L-composite) and 0.32 W·m^-1 K^-1 (R-composite)). Moreover, these two kinds of W/VO₂ transparent wood composites both show an outstanding thermoregulation ability when they are used as windows. A significant amount of heat (from a simulated light source) was reflected by VO₂ NPs, and as a result, the indoor temperature of a demo system had a significant slower temperature increase rate when compared with that for a similar system with a common glass panel applied. Novel transparent wood composites combining a low thermal conductivity wood template and thermochromic VO₂ NPs provide a potential solution for replacement of heavy, high thermal conductivity, and infrared transparent glass but still meet indoor occupancy view perception.

Preparation of solar-enhanced AlZnO@carbon nano-substrates for remediation of textile wastewaters

Photoactive aluminum doped ZnO (AlZnO) was synthesized by sol-gel method. After that, AlZnO photocatalyst was deposited on five carbon-based materials (CBMs) using ultrasonic route followed by solid-state mixing using ball mill. The CBMs used were polyaniline (PANI), carbon nitride (CN), carbon nanotubes (CNT), graphene (G), and carbon nanofibers (CNF). The crystal phases, elemental compositions, morphological, and optical properties of the AlZnO@CBMs composites were investigated. Experimental results revealed that two of AlZnO@CBMs composites exhibited superior bleaching efficiency (100% removal) and photocatalytic stability (three cycles) for 50 μmol/L Methylene Blue (MB) contaminated water after 60 min irradiation in visible light at pH 6.5, 0.7% H₂O₂, and 5 g/L inorganic salts. Under optimum conditions, AlZnO@CBMs nanocomposites were employed for the treatment of mixed dyestuffs composed of MB, Methyl Orange (MO), Astrazone Blue FRR (BB 69), and Rhodamine B (RhB) dyes under dark, ultraviolet, visible, and direct sunlight. For mixed dyestuffs, the AlZnO@G achieved the highest dye sorption capacity (60.91 μmol dye stuffs/g) with kinetic rate 8.22 × 10^-3 min^-1 in 90 min via multi-layer physisorption (Freundlich isotherm) on graphene sheet. In additions, AlZnO@CN offered the highest photo-kinetic rate (K_photo) of ~54.1 × 10^-3 min^-1 (93.8% after 60 min) under direct sunlight. Furthermore, the selective radical trapping experiment confirmed that the holes and oxidative superoxide radicals are crucial on dyes photodegradation pathway. Owing to their superior performance, AlZnO@G and AlZnO@CN nanocomposites can offer an effective in-situ solar-assisted adsorption/photocatalytic remediation of textile wastewater effluents.