THE DESIGN AND SYNTHESIS OF NEW ORGANIC DITHIOLS FOR ENVIRONMENTAL APPLICATIONS

A thiol molecule, 2,6-pyridinediamidoethanethiol (PB9), was synthesized based on the pyridine-2,6-dicarboxamide scaffold with appended cysteamine groups. PB9 acts as an effective chelator for Pb(II) due to multiple binding sites (N3S2) through irreversible binding precipitating Pb(II). Removal of aqueous Pb(II) from solution was demonstrated by exploring the effects of time, initial PB9:Pb(II) ratios, pH, exposure time, and solution temperature. After 15 min the Pb(II) concentrations were reduced from 50.00 ppm to 0.30 ppm (99.4%) and 0.25 ppm (99.5%) for PB9:Pb ratios of 1:1 and 2:1, respectively. Removal of \u3e 93% Pb(II) was observed over multiple pH values with negligible susceptibility for leaching over time. The thermodynamic studies reveal that the removal of Pb(II) from solution is an entropically driven, spontaneous process. Solution-state (UV−vis, 1H-NMR, 13C- NMR) along with solid-state (IR, Raman, and thermal) studies of PB9/Pb(II) compounds were performed. UV-vis displays a global maximum at 274 nm and a local maximum at 327 nm for ligand-to-metal charge transfer S- 3p to Pb2+ 6p, and intraatomic Pb2+ 6s to Pb2+ 6p transitions. FT-IR absorption spectra show significant absorption bands corresponding to amide I (C=O stretching) and amide II bands (C-N stretching, NH bending). The spectral shifting due to coordination of the amidic and pyridinic N to Pb(II) and further covalent bonding with sulfur was observed. Probable PB9 + Pb(II) interactions are proposed based on the techniques above mentioned. The molecular structure was designed as PB9 behaving like a bis-deprotonated ligand with an N3S2 donor set to give Pb(II) a trigonal bipyramidal environment with non-stereochemically active s electrons. The existence of a cyclic oligomeric (PB9)4(Pb)4 or polymeric (PB9)ꝏ(Pb)ꝏ structure is evidenced by broad melting point, insolubility in most common solvents, and amorphous powder XRD. Moreover, PB9 also exhibits high sensitivity and selectivity towards Fe(III) over other metal ions by fluorescent quenching. Theoretical studies comprising Benesi- Hildebrand, and studies such as Job’s plot, Stern-Volmer (S-V), and detection limits illustrate higher sensing abilities, possible dynamic and static quenching, and reversibility of binding. The quenching efficiency found by S-V is 7.42 ± 0.03 × 103 M−1. Job’s plot indicates the molar binding ratio of PB9: Fe(III) as 1:1 with a higher apparent association constant of 9.537 × 103 M–1 from the Benesi- Hildebrand plot. A linear range of Fe(III) (0 – 80 µM) with a detection limit of 0.59 µM (0.003 ppm) was found. The obtained detection limit was much lower than the maximum allowable limit of Fe(III) (0.3 ppm) regulated by EPA in drinking water. PB9-sensor exhibits visible color change from colorless to yellow acting like a naked-eye detector for Fe(III). In a separate study, 2,2\u27-(isophthalolybis(azanediyl))bis-3-mercaptopropanoic acid (AB9) was coupled to amine-functionalized silica and silica-coated magnetic nanoparticles (with magnetite, Fe3O4, core). This exploration was conducted for achieving \u3e 15 ppb (EPA level in drinking water) by a previously established method in the lab. The impact of initial concentration, pH, exposure time, and adsorbent dosage on the adsorption properties of Pb(II) from an aqueous solution was studied and optimized. Characterization was performed with ICP, FT-IR, Raman, XRD, TEM, and SEM. Results revealed successful fabrication of AB9 on mesoporous silica and MNP surfaces without introducing crystalline impurities. Indeed, an added advantage for AB9-MNP over AB9-silica is its magnetic nature, whereby a magnet was used to isolate the Pb(II)-containing (solid) composite from the treated water. The \u3e 99.9% removal of Pb(II) was obtained by AB9-MNP with detectable Pb(II) dropping below 15 ppb EPA level. The obtained equilibrium results were inserted in various adsorption isotherm models, including Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich. The data was in agreement with the Langmuir model, suggesting a dominant chemical adsorption mechanism on mesoporous AB9- silica and AB9-MNP with monolayer coverage. Maximum adsorption capacities were 22.05, 24.80, 35.57, and 56.40 mg/g, respectively, for silica, AB9-silica, MNP, and AB9-MNP. This demonstrates that a thiol group improves the adsorption capacity of Pb(II). This is an eco-friendly modification with rapid magnetic separation and chemicals utilizing HSAB to form stable compounds. Lack of complicated operations, extensive reaction times, high temperatures or high pressures, and toxic/ harmful reaction media make these AB9-MNP a good candidate for aqueous Pb(II) removal

Smart and Safe packaging

In line with the latest innovations in the packaging field, this joint project aims at implementing new and innovative micro- and nanoparticles for the development of active and intelligent packaging solutions dedicated to food and medical packaging applications. More specifically, the project combines two major developments which both falls within the scope of active and intelligent packaging. In this work, a specific focus was given to the development of an antibacterial packaging solution and to the development of smart gas sensors. The antibacterial strategy developed was based on the combination of two active materials - silver nanowires and cellulose nanofibrils - to prepare antibacterial surfaces. The formulation as an ink and the deposition processing has been deeply studied for different surface deposition processes that include coatings or screen-printing. Results showed surfaces that display strong antibacterial activity both against Gram-positive and Gram-negative bacteria, but also interesting properties for active packaging applications such as a highly retained transparency or enhanced barrier properties. Regarding the second strategy, gas sensors have been prepared using a combination of Copper benzene-1,3,5-tricarboxylate Metal Organic Framework and carbon-graphene materials, deposited on flexible screen-printed electrodes. The easy-to-produce and optimized sensors exhibit good performances toward ammonia and toward humidity sensing, proving the versatility and the great potential of such solution to be adapted for different target applications. The results of this project lead to innovative solutions that can meet the challenges raised by the packaging industry

Wearable Nano-Based Gas Sensors for Environmental Monitoring and Encountered Challenges in Optimization

With a rising emphasis on public safety and quality of life, there is an urgent need to ensure optimal air quality, both indoors and outdoors. Detecting toxic gaseous compounds plays a pivotal role in shaping our sustainable future. This review aims to elucidate the advancements in smart wearable (nano)sensors for monitoring harmful gaseous pollutants, such as ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), sulfur dioxide (SO2), ozone (O3), hydrocarbons (CxHy), and hydrogen fluoride (HF). Differentiating this review from its predecessors, we shed light on the challenges faced in enhancing sensor performance and offer a deep dive into the evolution of sensing materials, wearable substrates, electrodes, and types of sensors. Noteworthy materials for robust detection systems encompass 2D nanostructures, carbon nanomaterials, conducting polymers, nanohybrids, and metal oxide semiconductors. A dedicated section dissects the significance of circuit integration, miniaturization, real-time sensing, repeatability, reusability, power efficiency, gas-sensitive material deposition, selectivity, sensitivity, stability, and response/recovery time, pinpointing gaps in the current knowledge and offering avenues for further research. To conclude, we provide insights and suggestions for the prospective trajectory of smart wearable nanosensors in addressing the extant challenges