No abstract

Silica gels offer excellent wear resistance, high chemical stability, good insulation, and light transmittance, are therefore promising to engineer 2D sensing films. However, their practical applications are greatly hampered by their poor structural stability, low sensitivity, reliability, and repeatability. Incorporation of nanoelements into glasses and ceramics is a promising new pathway to tackle these challenges. Unfortunately, it is difficult to disperse nanoparticles uniformly in any glass and ceramics. Herein, a facile sol–gel approach is applied to synthesize novel silica gel nanocomposites with dispersed nanoparticles (NPs) as additives and thymol blue as an indicator. Titanium dioxide (TiO2) NPs with a diameter of 5 nm can be dispersed uniformly in the silica gel, with enhanced modulus and hardness (up to 230% and 138%, respectively) and good alkaline resistance. The addition of nanoparticles improves the film's stability, sensitivity, and repeatability of spectral responses (in pH 1–12), and reduces the indicator leakage. The interaction of indicator with silica gel substrate, nanoparticles, and H+ is analyzed to elucidate the principle of reversible color change. This novel simplified method to produce glass‐like functional materials under much lower temperatures is groundbreaking in materials science and engineering.

Ag-Ag 2 S heterodimers with good dispersibility were prepared in polyethylene glycol 400 (PEG400) at 160°C. The possible formation mechanism was proposed along the "CH 3 COOAg/Ag 2 S-Ag 2 O/Ag 2 S-Ag/Ag 2 S" route. The products [a] Figure 4. (A) The XRD patterns of the products from the mixture of PEG400, AgNO 3 and S powder: (a) 100°C, 10 min, (b) 100°C, 30 min, (c) 120°C, 10 min. (B) The possible growing mode of Ag-Ag 2 S heterodimers.4052 uid was obtained. The postprocessing of the products were the same as that of the Ag-Ag 2 S heterodimers. Preparation of Ag 2 S Nanomaterials4 mmol sulfur powder were weighed into a 100 mL round flask while some 40 mL PEG400 and 1 mmol AgNO 3 were added. The mixture was kept at 100°C for 10 min under mild magnetic stirring and then the black turbid liquid was obtained. The postprocessing of the products were the same as that of the Ag-Ag 2 S heterodimers. Conflicts of InterestThere are no conflicts to declare.

In order to develop a stable and sensitive layer for optical pH sensors which can be used in a wide pH range with long service life, we prepared an α-Al 2 O 3 /organo-modified silica pH composite sensing film by a sol-gel method with thymol blue as the indicator and α-Al 2 O 3 as the nano-reinforced filler. The α-Al 2 O 3 nanoparticles enable the pH sensing film to test solutions in the pH range of 1-12, with good reversibility, sensitivity and excellent resistance to strong acids and bases. Its alkaline resistance at pH = 12 is far superior to its silica counterparts, and it can remain stable for over 22 days at pH = 12. This study provides theoretical and experimental support for improving the acid and alkaline resistance of the silica gels. The α-Al 2 O 3 / organo modified pH sensing film is expected to provide stable pH testing in strongly alkaline environment (pH = 12) and have wide application prospects.