Diphenylacetylene Polymer Nanofiber Mats Fabricated by Freeze Drying: Preparation and Application for Explosive Sensors

Copolymers of 4-Trimethylsilyl Diphenyl Acetylene and 1-Trimethylsilyl-1-Propyne: Polymer Synthesis and Luminescent Property Adjustment

Poly(4-trimethylsilyl diphenyl acetylene) (PTMSDPA) has strong fluorescence emission, but its application is limited by the effect of aggregation-caused quenching (ACQ). Copolymerization is a commonly used method to adjust the properties of polymers. Through the copolymerization of 4-trimethylsilyl diphenyl acetylene and 1-trimethylsilyl-1-propyne (TMSP), we successfully realized the conversion of PTMSDPA from ACQ to aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AEE). By controlling the monomer feeding ratio and with the increase of the content of TMSDPA inserted into the copolymer, the emission peak was red-shifted, and a series of copolymers of poly(TMSDPA-co-TMSP) that emit blue-purple to orange-red light was obtained, and the feasibility of the application in explosive detection was verified. With picric acid (PA) as a model explosive, a super-quenching process has been observed, and the quenching constant (K_SV) calculated from the Stern-Volmer equation is 24,000 M^-1, which means that the polymer is potentially used for explosive detection.

Effect of polycaprolactone nanofibers loaded with oxytetracycline hydrochloride and zinc oxide as an adjunct to SRP on GCF lipocalin-2 levels in periodontitis patients: A clinical and laboratory study

Background. The aim of this study was the clinical and laboratory evaluation of using polycaprolactone (PCL) nanofibers loaded with oxytetracycline hydrochloride (OTC) and zinc oxide (ZnO) as an adjunct to mechanical therapy in managing stage II grade A periodontitis patients concerning GCF lipocalin2- levels. Methods. Fifty stage II grade A periodontitis patients (27 women and 23 men, with an age range of 30‒60) were enrolled in the study. The patients were randomly assigned to five equal groups and treated with scaling and root planing (SRP), followed by local application of PCL nanofibers: group I: SRP + PCL loaded with OTC and ZnO, group II: SRP + PCL loaded with OTC, group III: SRP + PCL loaded with ZnO, group IV: SRP + unloaded PCL, and group V: SRP alone. Additionally, 10 healthy subjects with healthy periodontium (group VI) (age- and gender-matched) served as the negative control. Nanofibers were applied in the selected pockets of periodontitis patients in groups I to IV once weekly for two months. All the participants were examined clinically by assessing periodontal indices (gingival index, plaque index, pocket depth, and clinical attachment level), and biochemically by assessing GCF lipocalin-2 levels. Results. Compared to controls, periodontitis groups (I, II, III, IV, and V) showed significant elevation of both clinical parameters and GCF lipocalin2- levels at baseline. In addition, these parameters improved significantly after treatment, which was more pronounced in groups I, II-, and III) compared to groups IV and V. However, it did not reach normal values. Conclusion. In association with SRP, PCL nanofibers loaded with OTC and ZnO had beneficial therapeutic effects at both clinical and laboratory levels.

High-Pressure Synthesis and Gas-Sensing Tests of 1-D Polymer/Aluminophosphate Nanocomposites

Recently, filling zeolites with gaseous hydrocarbons at high pressures in diamond anvil cells has been carried out to synthesize novel polymer-guest/zeolite-host nanocomposites with potential, intriguing applications, although the small amount of materials, 10^-7 cm³, severely limited true technological exploitation. Here, liquid phenylacetylene, a much more practical reactant, was polymerized in the 12 Å channels of the aluminophosphate Virginia Polytechnic Institute-Five (VFI) at about 0.8 GPa and 140 °C, with large volumes in the order of 0.6 cm³. The resulting polymer/VFI composite was investigated by synchrotron X-ray diffraction and optical and ¹H, ¹³C, and ²⁷Al nuclear magnetic resonance spectroscopy. The materials, consisting of disordered π-conjugated polyphenylacetylene chains in the pores of VFI, were deposited on quartz crystal microbalances and tested as gas sensors. We obtained promising sensing performances to water and butanol vapors, attributed to the finely tuned nanostructure of the composites. High-pressure synthesis is used here to obtain an otherwise unattainable true technological material.

Highly emissive 'frozen-in' conjugated polymer nanofibers

Conjugated-polymer nanofibers with a thermodynamically stable, coarsened, disordered structure in an amorphous glassy state were fabricated via a freeze-drying method using a poly(diphenylacetylene) derivative. The nanofibers were extremely emissive, with a fluorescence (FL) quantum yield of approximately 0.34, which was much higher than that of both the cast film (0.02) and the solution (0.21). Similarly, the amplitude-weighted average FL lifetime of the nanofibers was 0.74 ns, which was much longer than that of the film (0.29 ns) and the solution (0.57 ns). This unusual and enhanced FL-emission behavior was attributed to the abruptly quenched chain structure that was created by the freeze-drying process. The polymer chains in the nanofibers remained frozen-in and the side phenyl rings were retained in a relaxed state. The metastable chains did not undergo vibrational relaxation and collisional quenching to generate the radiative emission decay effectively.

Fluorescence based explosive detection: from mechanisms to sensory materials

The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large number of emissive sensing materials have been developed for the detection of explosives in vapor, solution, and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramolecular systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.

Fluorescent diphenylfluorene-pyrenyl copolymer with dibenzothiophene-S,S-dioxide and adamantane units for explosive vapor detection

This proposed strategy of incorporating SO units can be used as a promising approach to the development of fluorescent conjugated sensing materials.