Preparation of 1, 3, 6, 8-Pyrenesulfonic Acid Tetrasodium Salt Dye-Doped Silica Nanoparticles and Their Application in Water-Based Anti-Counterfeit Ink

A rapid and portable fluorescence spectroscopy staining method for the detection of plastic microfibers in water

We propose a simple technique for microplastic detection based on their interaction with a hydrophilic and anionic fluorescent dye 1,3,6,8 pyrene tetrasulfonate (PTSA). Synthetic microfibers derived from surgical face masks (an abundantly generated plastic waste post COVID) were considered as model microplastics. The interactions between microfibers and the dye were studied as a function of physiological parameters (pH, contact time and temperature), external agents, dye dosage and polymer variants. A pocket-sized photometer (by Lovibond Tintometer group) was employed for the detection and further validated using advanced equipment set-ups (fluorescence microscope, Fourier transform infrared spectroscopy and benchtop spectrofluorometer). Risk assessment studies were conducted on Artemia salina as a model organism. As a risk mitigation strategy, dye recovery followed by sunlight mediated degradation were performed. The detection study was performed in real water samples collected from fresh, estuarine and seawater samples spiked with microfibers. As an outcome, an optimized standard operational conditions were determined for the effective detection of synthetic microfibers. The data obtained could have scientific and industrial impact, in particular for experts working in the broad arena of clean water, who are specifically interested in developing cost-effective solutions for effective detection and biomonitoring of emerging pollutants.

Perpendicular Alignment of Covalent Organic Framework (COF) Pore Channels by Solvent Vapor Annealing

Covalent organic frameworks (COFs) have showcased great potential in diverse applications such as separation and catalysis, where mass transfer confined in their pore channels plays a significant role. However, anisotropic orientation usually occurs in polycrystalline COFs, and perpendicular alignment of COF pore channels is ultimately desired to maximize their performance. Herein, we demonstrate a strategy, solvent vapor annealing, to reorient COF pore channels from anisotropic orientation to perpendicular alignment. COF thin films are first synthesized to have flexible N-H bonds in their skeletons, thus having structural mobility to enable molecular rearrangement. A solvent with low relative permittivity and a conjugated structure is then identified to have a strong affinity toward the COFs, allowing its vapor to easily penetrate into the COF interlayers. The solvent vapor weakens the π-π interaction and consequently allows the COF monolayers to dissociate. The COF monolayers undergo a reorientation process that converts from random stacking into the face-on stacking fashion, in which the through COF pores are perpendicularly aligned. The aligned COF film exhibits high separation precision toward ions featuring a size difference down to 2 Å, which is 8 times higher than that of the anisotropically oriented counterpart. This work opens up an avenue for COF orientation regulation by solvent vapor annealing and reveals the essential role of the perpendicular alignment of COF pore channels to enable precision separations.