A Co ion adsorbent was prepared using electrospun porous polyacrylonitrile (PAN) nanofibers, featuring easy recovery for reuse compared with a nanoparticle-based adsorbent. As an efficient ligand for Co ions, ethylenediaminetetraacetic acid (EDTA) was introduced on the surface of porous PAN nanofibers with the aid of a branched polyethyleneimine (PEI) linker to obtain an adsorbent with carboxylic acid groups. On the adsorbent surface, the carboxylic acid from EDTA could adsorb Co ions via ion exchange and amine groups from PEI that remained after EDTA functionalization played a role in coordinating Co ions. The amine and carboxylic acid groups were simultaneously involved in the adsorption on the surface, making it possible to remove Co ions over a wide pH range. An investigation of the adsorption isotherms and kinetics of the nanofibrous adsorbent indicated that monolayer chemisorption was achieved with a maximum Co ion adsorption capacity of 8.32 mg/g. In addition, radioactive 60Co was efficiently removed by the adsorbent with a removal extent of more than 98%. Considering the easy separation from Co ion solution and regeneration of the nanofibrous adsorbent and its availability in a wide pH range, the adsorbent has great advantages in practical applications.
o-Phenylazonaphthol (o-PAN) derivatives including 6-bromo-1-((4-bromophenyl)diazenyl)naphthalen-2-ol (AN-Br-OH) and 1-phenylazo-2-naphthol (AN-OH, known as Sudan I (Color Index 12055)) were synthesized to investigate their fluorogenic behaviors, in which their aggregated-induced emission (AIE) is reported. The o-PANs showed a two-photon absorption. The protection of hydroxyl groups in o-PANs was used for fluorescence imaging of esterase-expressed HepG2 cells, which is potentially suitable for sensing and two-photon cell imaging applications.
To advance cancer treatment, we have developed a novel composite material consisting of conjugated polymer dots (CPDs) and Prussian blue (PB) particles, which were immobilized on, and encapsulated within, silica particles, respectively. The CPDs functioned as both a photosensitizer and a photodynamic agent, and the PB acted as a photothermal agent. The silica platform provided a biocompatible matrix that brought the two components into close proximity. Under laser irradiation, the fluorescence from the CPDs in the composite material enabled cell imaging and was subsequently converted to thermal energy by PB. This efficient energy transfer was accomplished because of the spectral overlap between the emission of donor CPDs and the absorbance of acceptor PB. The increase in local temperature in the cells resulted in a significant increase in the amount of reactive oxygen species (ROS) generated by CPDs, in which their independent use did not produce sufficient ROS for cancer cell treatment. To assess the impact of the enhanced ROS generation by the composite material, we conducted experiments using cancer cells under 532 nm laser irradiation. The results showed that with the increase in local temperature, the generated ROS increased by 30% compared with the control, which did not contain PB. When the silica-based composite material was positioned at the periphery of the tumor for 120 h, it led to a much slower tumor growth than other materials tested. By using a CPD-based photodynamic therapy platform, a new simplified approach to designing and preparing cancer treatments could be achieved, which included photothermal PB-assisted enhanced ROS generation using a single laser. This advancement opens up an exciting new opportunity for effective cancer treatment.
A Janus-type TiO2-based micromotor was fabricated, in which visible-light-absorbing conjugated polymer dots (CPdots) were asymmetrically introduced to the TiO2 hemisphere. The wax-in-water Pickering emulsion method enabled obtaining Janus-type TiO2 microspheres decorated with CPdots, which were attached by electrostatic interaction. Electrons and holes were generated in the CPdots upon visible light absorption and the generated hole oxidized H2O2 used as a fuel. TiO2 suppressed the recombination of electrons and holes by accepting excited electrons from CPdots. The TiO2-based micromotor was moved by O2 produced under visible light. In addition, when H2O2 was decomposed, electrophoresis and diffusiophoresis occurred because of concentration gradient. A SiO2-based micromotor showed a much slower movement, indicating the necessity for TiO2. In addition, the moving TiO2 micromotor showed effectiveness in dye degradation via photocatalysis under visible light, irrespective of the lack of visible light absorbance by TiO2.
Plastic scintillators, as a type of radioactive radiation detectors, have shown great potential in the field of nuclear radiation detection because of their well-studied scintillating property. Although much effort has been dedicated to developing plastic scintillators with high detection efficiency, materials with excellent monitoring performance are still needed. A covalent-integration strategy was implemented in the fabrication of a series of polyvinyltoluene (PVT) scintillators containing a polyfluorene-based conjugated polymer (CP) for the detection of radioactive nuclides of Sr-90 and C-14; the scintillators feature an excellent cascade energy transfer from beta radiation to the CP. To act as an antenna for β-radiation harvesting, the fluorescent dopant 2,5-diphenyloxazole (PPO) was covalently introduced to the CP side chain. The PPO-functionalized CP was embedded in PVT to fabricate the polymer-blend scintillator, showing enhanced photomultiplier-detectable signal via efficient energy transfer. The cascade energy transfer, in which the β-radiation energy was absorbed by PVT and PPO and was finally transferred to CP, was successfully demonstrated. The scintillator showed a high detection efficiency of up to 50% under Sr-90 radiation, i.e., 30% higher efficiency than a PVT-containing simple mixture of CP and PPO, and it was also better than a conventional scintillator that contained PVT and PPO.
To overcome one of the disadvantages of ultraviolet absorbance of the wide-bandgap semiconductor TiO2, visible-light-driven composite photocatalysts were fabricated through chemically bound conjugated polymers (CPs) on a TiO2 surface. The interfacial chemical bonding between TiO2 and the CP could act as a linker for close proximity of two species for easy transfer of the excited electrons from the CP to the conduction band of TiO2, which significantly enhanced the photocatalytic efficiency in the visible range. The robust covalent bond between the CP and TiO2 led to increased stability during photocatalysis, enabling repeated use after simple washing. Moreover, the hydrophilic surface of the photocatalyst could be fabricated by modifying the CP on the photocatalyst's surface. Such a wettability change of the photocatalyst's surface allowed the photocatalyst to be used in reduction and oxidation reactions with high efficiency in both water and organic solvents. The combination of the visible light-harvesting capacity of the CP and the photocatalytic activity of TiO2 enabled versatile uses of the composite photocatalysts.
Electrospun, emission color-tunable nanofibrous sheets were fabricated by multinozzle electrospinning equipped with a secondary electrode for the preparation of white-emissive sheets under a single excitation source, manipulating energy transfer between dyes. By control of the concentration of commercially available red, green, and blue dyes in the matrix polymer [poly(methyl methacrylate)], emission color tuning can be easily accomplished because each dye is located in spatially separated fibers to maintain enough distance to prevent or suppress energy transfer, allowing white-light emission. The application of dye separation for the white-light emission upon excitation with a blue light-emitting-diode lamp is demonstrated, indicative of its potential application for the easy and facile tuning of fluorescence color toward flexible illumination.
A novel chemical warfare agent sensor based on conjugated polymer dots (CPdots) immobilized on the surface of poly(vinyl alcohol) (PVA)–silica nanofibers was prepared with a dots-on-fibers (DoF) hybrid nanostructure via simple electrospinning and subsequent immobilization processes. We synthesized a polyquinoxaline (PQ)-based CP as a highly emissive sensing probe and employed PVA–silica as a host polymer for the elctrospun fibers. It was demonstrated that the CPdots and amine-functionalized electrospun PVA–silica nanofibers interacted via an electrostatic interaction, which was stable under prolonged mechanical force. Because the CPdots were located on the surface of the nanofibers, the highly emissive properties of the CPdots could be maintained and even enhanced, leading to a sensitive turn-off detection protocol for chemical warfare agents. The prepared fluorescent DoF hybrid was quenched in the presence of a chemical warfare agent simulant, due to the electron transfer between the quinoxaline group in the polymer and the organophosphorous simulant. The detection time was almost instantaneous, and a very low limit of detection was observed (∼1.25 × 10–6 M) with selectivity over other organophosphorous compounds. The DoF hybrid nanomaterial can be developed as a rapid, practical, portable, and stable chemical warfare agent-detecting system and, moreover, can find further applications in other sensing systems simply by changing the probe dots immobilized on the surface of nanofibers.
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