Preparation of modified humic acid/TiO2/P(AA-co-AM) nanocomposite hydrogels with enhanced dye adsorption and photocatalysis.

A novel composite hydrogel with exceptional adsorption and photocatalytic properties was synthesized using modified coal-based humic acid (HA-C), modified titanium dioxide (TiO2) nanoparticles, acrylic acid (AA), and acrylamide (AM) as precursors. The modification of HA-C and TiO2 significantly enhances the structural support provided by the hydrogel for photocatalytic components. Moreover, we investigated the effects of monomer ratio, dye concentration, temperature, and pH on the material properties. Additionally, we tested the mechanical strength, swelling behavior, and reusability of the hydrogels. The composite hydrogel's adsorption performance and synergistic adsorption-photocatalytic performance were evaluated based on its removal rate for both absorbed and degraded methylene blue (MB). Remarkably, incorporating HA-C greatly improved the adsorption efficiency of the composite hydrogel for methylene blue to a maximum capacity of 1490 mg g-1. Furthermore, TiO2 nanoparticles in the structure promoted MB degradation with an efficiency exceeding 96.5%. The hydrogel exhibited excellent recoverability and reusability through nine cycles of adsorption/desorption as well as six cycles of degradation.

In situ growth and optical gas adsorption performance of Zn(ii) metal-organic framework membranes at room temperature.

A series of Zn(ii) metal-organic framework membranes, [Zn2(bdc)2(dpNDI)]n (where bdc = terephthalic acid and dpNDI = N,N'-di(4-pyridyl)-1,4,5,8-naphthalenediimide), were grown on a tin-diffused glass substrate using an in situ growth method at room temperature (20 °C). [Zn2(bdc)2(dpNDI)]n thin films were optically transparent and characterized by absorbance, thickness, refractive index and fluorescence techniques. After 20 h of growth, they displayed a complete honeycomb framework with a larger pore size (380 nm), uniform surface and lower refractive index. Also, it is demonstrated that [Zn2(bdc)2(dpNDI)]n thin films exhibited a greater adsorption response to meta-xylene gas with the coexistence of interferents like toluene, styrene and benzene gases, as measured by the planar optical waveguide (POWG) gas detection system under ultraviolet light (395 nm) irradiation. Moreover, when the [Zn2(bdc)2(dpNDI)]n thin film adsorbs meta-xylene gas, the intramolecular hydrogen bonds in the thin film framework were strengthened because of the accumulation of meta-xylene. At room temperature, the meta-xylene gas adsorption kinetics followed a pseudo-second-order (PSO) model, and the adsorption capacity on the unit surface was 6.46 µg cm-2. The highly selective meta-xylene adsorption performance of the [Zn2(bdc)2(dpNDI)]n thin film makes it an ideal sensing material for the recognition of harmful gases that are poisonous to the human body and the environment.

Preparation of high strength, self-healing conductive hydrogel based on polysaccharide and its application in sensor.

The development of cost-effective, eco-friendly conductive hydrogels with excellent mechanical properties, self-healing capabilities, and non-toxicity holds immense significance in the realm of biosensors. The biosensors demonstrate promising applications in the fields of biomedical engineering and human motion detection. A unique double-network hydrogel was prepared through physical-chemical crosslinking using chitosan (CS), polyacrylic acid (AA), and sodium alginate (SA) as raw materials. The prepared double-network hydrogels exhibited exceptional mechanical properties, as well as self-healing and conductive capabilities. Polyacrylic acid as the first layer network, while chitosan and sodium alginate were incorporated to establish the second layer network through electrostatic interactions, thereby imparting self-healing and self-recovery properties. The hydrogel was subsequently immersed in the salt solution to induce network winding. The mechanical robustness of the hydrogel was significantly enhanced through synergistic coordination of covalent and non-covalent interactions. When the concentration of sodium alginate was 20 g/L, the double-network hydrogel exhibits enhanced mechanical properties, with a tensile fracture stress of up to 1.31 MPa and a strength of 4.17 MPa under 80% compressive deformation. Furthermore, the recovery rate of this double-network hydrogel reached an impressive 89.63% within a span of 30 min. After 24 h without any external forces, the self-healing rate reached 26.11%, demonstrating remarkable capabilities in terms of self-recovery and self-healing. Furthermore, this hydrogel exhibited consistent conductivity properties and was capable of detecting human finger movements. Hence, this study presents a novel approach for designing and synthesizing environmentally friendly conductive hydrogels for biosensors.

Preparation and Photocatalytic Performance of Sodium Alginate/Polyacrylamide/Polypyrrole-TiO2 Nanocomposite Hydrogels.

The application of photocatalysis technology in environmental pollution treatment has garnered increasing attention, and enhancing the photocatalytic efficiency and recyclability of photocatalysts represents a pivotal research focus for future endeavors. In this paper, polypyrrole titanium dioxide nanocomposite (PPy-TiO2) was prepared using in situ polymerization method and dispersed in sodium alginate/polyacrylamide (SA/PAM) hydrogel matrix to prepare SA/PAM/PPy-TiO2 nanocomposite hydrogels. The nanocomposite hydrogels were characterized by XPS, FT-IR, XRD, TGA, SEM, and TEM. The results showed that the composite materials were successfully prepared and PPy-TiO2 was uniformly dispersed in the hydrogel matrix. The incorporation of PPy in the SA/PAM/TiO2 composite hydrogel resulted in enhanced visible light absorption, reduced recombination efficiency of photoelectron-hole pairs in TiO2, and facilitated the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) under sunlight irradiation. The photocatalytic efficiency of the composite hydrogel for MB was nearly 100%, whereas for MO, it reached 91.85% after exposure to sunlight for 120 min. In comparison with nano-TiO2 and PPy-TiO2, the SA/PAM/PPy-TiO2 nanocomposite hydrogel exhibited a higher degradation rate of MB and demonstrated ease in separation and recovery from the reaction solution. Furthermore, even after undergoing five cycles of recycling, there was no significant decrease observed in photodegradation efficiency.

Ligand and solvent control of selectivity in the C-H activation of a pyridylimine-substituted 1-naphthalene; a combined synthetic and computational study.

The pyridylimine-substituted 1-naphthalenes, 2-(1-C10H7)-6-{CR[double bond, length as m-dash]N(2,6-i-Pr2C6H3)}C5H3N (R = Me HLMe, H HLH), react with Na2[PdCl4] in acetic acid at elevated temperature to afford either ortho-C-Hnaphthyl activated (LMe)PdCl (2ortho) or the unactivated adduct (HLH)PdCl2 (1b). Alternatively, 1b and its ketimine analogue (HLMe)PdCl2 (1a), can be prepared by treating (MeCN)2PdCl2 with either HLMe or HLH in chloroform at room temperature. Regio-selective ortho-C-H activation to form 2ortho can also be initiated by the thermolysis of 1a in acetic acid, while no reaction occurs under similar conditions with 1b. Interestingly, the C-H activation of HLMe to give 2ortho is found to be reversible with 100% deuteration of the peri-site occurring on reacting Na2[PdCl4] with HLMe in acetic acid-d4. By contrast, heating 1a in toluene gives a 55 : 45 mixture of 2ortho and its peri-activated isomer 2peri. Pure 2peri can, however, be obtained either from (LMe)PdOAc (3peri) by OAc/Cl exchange or by the sequential reactions of 1a with firstly silver acetate then with aqueous sodium chloride. Intriguingly, a peri to ortho interconversion occurs on heating 2peri in acetic acid to give 2ortho. DFT calculations have been used to investigate the C-H activation steps and it is found that in acetic acid ortho-C-H activation is kinetically and thermodynamically favoured but peri-CH activation is kinetically accessible (ΔΔG‡ = 2.4 kcal mol-1). By contrast in toluene, the reaction appears to be irreversible with the difference in barrier height for ortho- and peri-C-H activation being very small within the error of the method (ΔΔG‡ = 0.7 kcal mol-1), findings that are in agreement with the empirically observed product distribution for 2ortho and 2peri. Single crystal X-ray structures are reported for 1a, 1b, 2ortho and 2peri.