This work explores silica (SiO₂) extraction from sugarcane bagasse ash using NaOH solution. The obtained SiO₂ with 98 wt% purity is further used to synthesize zeolite NaA for CO₂ adsorption, showing comparable capacity to commercial NaA.

Zeolites in powder form have the potential to agglomerate, lowering access to active sites. Furthermore, a suspension of fine zeolite powder in liquid media is difficult to separate. Such drawbacks could be improved by dispersing zeolite crystals on support materials. This work demonstrates the dispersion of zeolite NaY crystals on bamboo wood by mixing the wood with zeolite gel before hydrothermal treatment. The syntheses were performed with acid-refluxed and non–refluxed wood. The phase of zeolites, particle distribution and morphology, zeolite content in the wood, and zeolite–wood interaction were investigated using X-ray diffraction, X-ray tomography, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption analysis, and X-ray photoelectron spectroscopy. Higher zeolite content and better particle dispersion were obtained in the synthesis with the acid–refluxed wood. The composite of NaY on the acid-refluxed wood was demonstrated to be an effective adsorbent for Ni(II) ions in aqueous solutions, providing a higher adsorbed amount of Ni(II) per weight of NaY.

N-Alkylation of tris(4-pyridyl) hexaazaphenalene (TPHAP) anions afforded corresponding pyridinium derivatives. These compounds typically existed in their dicationic states and exhibited significantly enhanced π–π interactions within stacked dimers due to a change in charge distribution induced by the pyridinium moieties. This behaviour was attributed to the reduction in the anion–anion repulsion between the HAP cores. In addition, the presence of substituted alkyl pyridinium groups and corresponding counter anions modified the molecular packing of these derivatives. Molecular orbital calculations of the pyridinium analogues revealed close similarity of their HOMO and LUMO to the unsubstituted TPHAP with significantly lowered energies. Solution-state electrochromism was investigated by in situ spectroelectrochemical analysis. The electrochemical reduction was accompanied by the appearance of new absorption bands in the visible and NIR ranges.

An optical sensor based on pyranine immobilized on aminopropyl-modified mesoporous silica films was developed for paraquat detection in aqueous solutions. An electrochemically assisted self-assembly method was used to deposit mesoporous silica film on fluorine-doped tin oxide glass. The obtained films were modified with various concentrations of 3-aminopropyl triethoxysilane (APTES) before the immobilization of pyranine. Cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy were used to characterize the films. Pyranine-immobilized films gave an emission at 506 nm with an excitation at 450 nm. The fluorescence signal was quenched in the presence of paraquat. The films modified with 3% APTES provided the optimum response to paraquat. The developed films had a linear response to paraquat in the concentration range of 1 to 10 ppm at the optimum conditions, with a detection limit of 0.80 ppm. The developed method was used to quantify paraquat in sugarcane peel and tap water samples with satisfactory results.