High-performance Ag-TiO2 nanoparticle composite catalyst synthesized by pulsed laser ablation in liquid: properties, mechanism and preparation studies

Precious metal doping can effectively improves the catalytic performance of TiO2. In this study, pulsed laser ablation in liquid (PLAL) is employed to integrate preparation with doping and control composite nanoparticle products by adjusting the laser action time to synthesise Ag-TiO2 composite nanoparticles with high catalytic performance. The generation and evolution of Ag-TiO2 nanoparticles are investigated by analysing particle size, microscopic morphology, crystalline phase, and other characteristics. The generation and doped-morphology evolution of composite nanoparticles are simulated based on thermodynamics, and the optimisation of Ag-doped structure on the composite nanomaterials is investigated based on density functional theory. The effect of Ag-TiO2 structural properties on its performance is examined under different catalytic conditions to determine optimal degradation conditions. In this study, the effect of laser ablation time on the doped structure during PLAL is analysed, which is of further research significance in exploring the structural evolution law of laser and composite nanoparticles, multi-variate catalytic performance testing, reduction of photogenerated carrier complexation rate, and expansion of its spectral absorption range, thereby providing the basis for practical production.

Novel multifunctional environmentally friendly degradable zeolitic imidazolate frameworks@poly (γ-glutamic acid) hydrogel with efficient dye adsorption function

Recently, metal-organic frameworks (MOFs) have been widely developed due to the rich porosity, excellent framework structure and multifunctional nature. Meanwhile, a series of MOFs crystals and MOF-based composites have been emerged. However, the widespread applications of MOFs are hindered by challenges such as rigidity, fragility, solution instability, and processing difficulties. In this study, we addressed these limitations by employing an in-situ green growth approach to prepare a zeolitic imidazolate frameworks-8@poly (γ-glutamic acid) hydrogel (ZIF-8@γ-PGA) with hierarchical structures. This innovative method effectively resolves the inherent issues associated with MOFs. Furthermore, the ZIF-8@γ-PGA hydrogel is utilized for dye adsorption, demonstrating an impressive maximum adsorption capacity of 1130 ± 1 mg/g for methylene blue (MB). The adsorption behavior exhibits an excellent agreement with both the kinetic model and isotherm. Meanwhile, because the adsorbent raw materials are all green non-toxic materials, multiple applications of materials can also be realized. Significantly, the results of antibacterial experiments showed that the ZIF-8@γ-PGA hydrogel after in-situ growth of ZIF-8 had better antibacterial properties. Thus, the ZIF-8@γ-PGA hydrogel has great potential for development in wound dressings, sustained drug owing to its biocompatibility and antibacterial activity.

First-Principles Computational Study of the Modification Mechanism of Graphene/Graphene Oxide on Hydroxyapatite

Due to its unique crystal structure and nano-properties, hydroxyapatite (HA) has become an important inorganic material with broad development prospects in electrical materials, for fire resistance and insulation, and in bone repair. However, its application is limited to some extent because of its low strength, brittleness and other shortcomings. Graphene (G) and its derivative graphene oxide (GO) are well known for their excellent mechanical properties, and are widely used to modify HA by domestic and foreign scholars, who expect to achieve better reinforcement and toughening effects. However, the enhancement mechanism has not been made clear. Accordingly, in this study, G and GO were selected to modify HA using the first-principles calculation method to explore the theory of interfacial bonding of composites and explain the microscopic mechanism of interfacial bonding. First-principles calculation is a powerful tool used to solve experimental and theoretical problems and predict the structure and properties of new materials with precise control at the atomic level. Therefore, the bonding behaviors of hydroxyapatite (100), (110) and (111) crystal planes with G or GO were comprehensively and systematically studied using first-principles calculation; this included analyses of the density of states and differential charge density, and calculations of interfacial adhesion work and elastic moduli. Compared to HA (100) and (111) crystal planes, HA (110) had the best bonding performance with G and with GO, as revealed by the calculation results. The composite material systems of HA (110)/G and HA (110)/GO had the smallest density of states at the Fermi level, the largest charge transfers of Ca atoms, the largest interfacial adhesion work and the most outstanding elastic moduli. These results provide a theoretical basis for the modification of HA to a certain extent, and are beneficial to the expansion of the scope of its application.

Effective fabrication of cellulose nanofibrils supported Pd nanoparticles as a novel nanozyme with peroxidase and oxidase-like activities for efficient dye degradation

Nanozyme-based dye degradation methods are promising for the remediation of water pollution. Though Pd nanoparticles (PdNPs) are known to act as nanozymes, their dye degradation capability has not been investigated. Low nanozyme activities, easy aggregation, difficulties in recovery and reuse are the major challenges in achieving this. For the first time, cellulose nanofibrils-supported PdNPs (PdNPs/PCNF) as a novel nanozyme with good peroxidase and oxidase-mimicking activities and easy recyclability is explored for dye degradation. An efficient and rapid method of PdNPs/PCNF preparation was demonstrated by adjusting the pH and microwave irradiation. Enzyme kinetic studies revealed good kinetic parameters and specific activities of 415 and 277 U/g for peroxidase and oxidase, respectively. PdNPs/PCNF offered 99.64% degradation of methylene blue within 12 min (0.468 min^-1) with 0.4 M H₂O₂ at pH 5.0. Mechanistic studies revealed the involvement of hydroxyl and superoxide radicals. Owing to the network-like structure of PCNF, films and foams were prepared, their dye degradation potentials were compared, and recyclability was tested. Successful degradation of mixed dye solutions and spiked real water samples was achieved and a continuous flow method was demonstrated using a foam-packed column.

Eco-friendly hybrid Paper-AgBr-TiO2 for efficient photocatalytic aerobic mineralization of ethanol

In this study, a facile and effective route to prepare hybrid photocatalysts (paper-TiO₂, paper-TiO₂-AgBr and paper-AgBr-TiO₂) has been reported. The preparation procedure consisted of the direct adsorption of the previously synthesized titania nanoparticles (TiO₂ sol) to generate the TiO₂ nanosphere and the immersion process in an aqueous suspension of AgBr to form the AgBr nanoclusters on paper fibers. The synthesis technology is economic, efficient, environmentally friendly and easy to implement even at industrial scale. A cellulose-based structure with well dispersed TiO₂ particles of around 1 μm and a pseudo-liquid coating of Ag⁺ and AgBr species was obtained. All the prepared photocatalysts demonstrated effective photocatalytic performance in gaseous phase ethanol degradation with simulated sunlight illumination, through the direct mineralization to CO₂ and the parallel reaction via acetaldehyde degradation. A relevant improvement in the photocatalytic activity was noticed when TiO₂ was associated with AgBr nanocrystals, with a higher effect observed when AgBr was loaded onto the paper surface prior to TiO₂. Ag-Ti interaction reduces the pair recombination rate and increases the available charge carriers generating reactive OH- radicals from both Ag-species and TiO₂, and O₂^- radicals from Ag⁺-AgBr species, which would be involved in the ethanol degradation process.

Palladium nanoparticles immobilized on polyethylenimine-derivatized gold surfaces for catalysis of Suzuki reactions: development and application in a lab-on-a-chip context

Gold surface-bound hyperbranched polyethyleneimine (PEI) films decorated with palladium nanoparticles have been used as efficient catalysts for a series of Suzuki reactions. This thin film-format demonstrated good catalytic efficiency (TON up to 3.4 × 10³) and stability. Incorporation into a quartz crystal microbalance (QCM) instrument illustrated the potential for using this approach in lab-on-a-chip-based synthesis applications.

Gold surface-bound hyperbranched polyethyleneimine (PEI) films decorated with palladium nanoparticles have been used as efficient catalysts for a series of Suzuki reactions in a lab-on-a-chip format.

Paper Functionalized with Nanostructured TiO2/AgBr: Photocatalytic Degradation of 2-Propanol under Solar Light Irradiation and Antibacterial Activity

A facile method to produce paper–TiO₂ decorated with AgBr nanoparticles by a mild hydrothermal process at 140 °C was reported. The synthesis method was based on the immersion of the paper in a ready-made suspension of TiO₂/AgBr, comprising TiO₂ sol solution prepared in acidic conditions and AgBr solution (10⁻⁴ M). A paper–TiO₂ sample was prepared and used as reference. The formation of crystalline phases of titanium oxide (TiO₂) and silver bromide (AgBr) was demonstrated by XRD, Raman and EDX analyses. The surface morphology of the TiO₂–AgBr was investigated by Field Effect Scanning Electronic Microscopy (FE–SEM). The photocatalytic performances of the prepared material were evaluated in the degradation of 2-propanol in the gas phase, under simulated sunlight illumination. Its antibacterial properties against Escherichia coli (E. coli) were also assessed. The efficiency of photodegradation and the anti-bacterial properties of paper–TiO₂–AgBr were attributed to an improvement in the absorption of visible light, the increased production of reactive oxygen species (ROS) and the low recombination of photogenerated charge carriers due to the synergistic effect between TiO₂ and AgBr/Ag nanoparticles.

Flexible Photocatalytic Paper with Cu2O and Ag Nanoparticle-Decorated ZnO Nanorods for Visible Light Photodegradation of Organic Dye

We report on the fabrication of flexible photocatalytic paper comprised of Cu₂O and Ag nanoparticle (NP)-decorated ZnO nanorods (NRs) and its application in visible light photodegradation of organic dye. ZnO NRs are first grown on a kraft paper substrate using a hydrothermal method. The NRs are subsequently decorated with Cu₂O, Ag, or both NPs formed by photoreduction processes. Scanning electron microscopy and X-ray diffraction analysis confirm the crystallinity of ZnO NRs. Transmission electron microscopy analysis confirms the compositions of the two types of NPs. Four different types of photocatalytic papers with a size of 10 × 10 cm² are prepared and used to degrade a 10-μM and 100-mL rhodamine B solution. The paper with Cu₂O and Ag NP-co-decorated ZnO NRs has the best efficiency with first-order kinetic constants of 0.017 and 0.041 min^-1 under the illumination of a halogen lamp and direct sunlight, respectively. The performance of the photocatalytic paper compares well with other substrate-supported ZnO nanocomposite photocatalysts. With the advantages of flexibility, light weight, nontoxicity, low cost, and ease of fabrication, the photocatalytic paper has good potential for visible light photocatalysis.

TiO₂-ZnO Binary Oxide Systems: Comprehensive Characterization and Tests of Photocatalytic Activity

A series of TiO₂-ZnO binary oxide systems with various molar ratios of TiO₂ and ZnO were prepared using a sol-gel method. The influence of the molar ratio and temperature of calcination on the particle sizes, morphology, crystalline structure, surface composition, porous structure parameters, and thermal stability of the final hybrids was investigated. Additionally, to confirm the presence of characteristic surface groups of the material, Fourier transform infrared spectroscopy was applied. It was found that the crystalline structure, porous structure parameters, and thermal stability were determined by the molar ratio of TiO₂ to ZnO and the calcination process for the most part. A key element of the study was an evaluation of the photocatalytic activity of the TiO₂-ZnO hybrids with respect to the decomposition of C.I. Basic Blue 9, C.I. Basic Red 1, and C.I. Basic Violet 10 dyes. It was found that the TiO₂-ZnO material obtained with a molar ratio of TiO₂:ZnO = 9:1 and calcined at 600 °C demonstrates high photocatalytic activity in the degradation of the three organic dyes when compared with pristine TiO₂. Moreover, an attempt was made to describe equilibrium aspects by applying the Langmuir-Hinsherlwood equation.

Highly selective and sensitive methanol gas sensor based on molecular imprinted silver-doped LaFeO3 core-shell and cage structures

Silver-doped LaFeO₃ molecularly imprinted polymers (SLMIPs) were synthesized by a sol-gel method combined with molecularly imprinted technology as precursors. The precursors were then used to prepare SLMIPs cage (SLM-cage) and SLMIPs core-shell (SLM-core-shell) structures by using a carbon sphere as the template and hydrothermal synthesis, respectively. The structures, morphologies, and surface areas of these materials were determined, as well as their gas-sensing properties and related mechanisms. The SLM-cage and SLM-core-shell samples exhibited good responses to methanol gas, with excellent selectivity. The response and optimum working temperature were 16.98 °C and 215 °C, 33.7 °C and 195 °C, respectively, with corresponding response and recovery times of 45 and 50 s (SLM-cage) and 42 and 57 s (SLM-core-shell) for 5 ppm methanol gas. Notably, the SLM-cage and SLM-core-shell samples exhibited lower responses (≤5 and ≤7, respectively) to other gases, including ethanol, ammonia, benzene, acetone, and toluene. Thus, these materials show potential as practical methanol detectors.

Remote Controlling DNA Hydrogel by Magnetic Field

DNA hydrogel has aroused widespread attention because of its unique properties. In this work, the DNA-modified magnetic nanoparticles were integrated into the mainframe of DNA hydrogel, resulting in DNA-MNP hydrogel. Under the magnetic field, this hydrogel can be remotely deformed into various shapes, driven to jump between two planes and even climb the hill. By applying various triggers, such as temperature, enzyme, and magnetic field, DNA-MNP hydrogel can specifically undergo sol-gel transition. This work not only imparts DNA hydrogel with a new fold of property but also opens a unique platform of such smart materials for its further applications.

Fabrication of Photocatalytic Paper Using TiO2 Nanoparticles Confined in Hollow Silica Capsules

TiO₂ nanoparticles (NPs) encapsulated in hollow silica spheres (TiO₂@HSSs) show a shielding-effect that can insulate photocatalytically active TiO₂ NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO₂@HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO₂@HSS, which has an ample void space between inner TiO₂ NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO₂@HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO₂@HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO₂@HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO₂ NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO₂ and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

Enhanced Analytical Performance of Paper Microfluidic Devices by Using Fe3O4 Nanoparticles, MWCNT, and Graphene Oxide

Spheres, tubes, and planar-shaped nanomaterials as Fe3O4 nanoparticles (MNPs), multiwalled carbon nanotubes (MWCNT), and graphene oxide (GO) were used for the first time to treat microfluidic paper-based analytical devices (μPADs) and create a biocompatible layer with high catalytic surface. Once glucose measurements are critical for diabetes or glycosuria detection and monitoring, the analytical performance of the proposed devices was studied by using bienzymatic colorimetric detection of this carbohydrate. The limit of detection values achieved for glucose with μPADs treated with MNPs, MWCNT, and GO were 43, 62, and 18 μM, respectively. The paper surface modification solves problems associated with the lack of homogeneity on color measurements that compromise the sensitivity and detectability levels in clinical diagnosis.

Earth-abundant stable elemental semiconductor red phosphorus-based hybrids for environmental remediation and energy storage applications

The photocatalytic generation of hydrogen and the photodegradation of organic dyes in wastewater using solar light, preferably visible light, have attracted considerable interest because they are clean, low-cost, and environmentally friendly processes.