A fluorescent perylene-assembled polyvinylpyrrolidone film: synthesis, morphology and nanostructure

Development of low-cost copper nanoclusters for highly selective "turn-on" sensing of Hg2+ ions

The development of low-cost earth abundant metal based fluorescent sensors for a rapid and selective nanomolar level detection of Hg²⁺ is essential due to the increasing world-wide concern of its detrimental effect on humans as well as the environment. Herein, we present a perylene tetracarboxylic acid functionalized copper nanoclusters (CuNCs) based "turn-on" fluorescence probe for highly selective detection of toxic Hg²⁺ ions. The fabricated CuNCs exhibited high photostability with emission maximum centered at 532 nm (λ_ex = 480 nm). The fluorescence intensity of CuNCs was remarkably enhanced upon the addition of Hg²⁺ over other competing ions and neutral analytes. Notably, the 'turn-on' fluorescence response exhibits highly sensitive detection limit as low as 15.9 nM (S/N ∼ 3). The time resolved fluorescence spectroscopy suggested the energy transfer between CuNCs and Hg²⁺ ions following either inhibited fluorescence resonance energy transfer (FRET) or surface modification of CuNCs during Hg²⁺ sensing. This study offers the systematic design and development of new fluorescent 'turn-on' nanoprobes for rapid and selective recognition of heavy metal ions.

Preparation of Structural Color on Cotton Fabric with High Color Fastness through Multiple Hydrogen Bonds between Polyphenol Hydroxyl and Lactam

Structural coloration is an important way to realize eco-friendly dyeing of textiles. Structural colored cotton fabric was obtained by fabricating a polydopamine (PDA) film on the white cotton fabric at different polymerization reaction times. PDA is prone to generate capillary tension during film formation, which damages the uniformity and interfacial bonding force of the film. Multiple hydrogen bonds will form between the lactam group of polyvinylpyrrolidone (PVP) and the phenolic hydroxyl group of PDA. The introduced hydrogen bonds will effectively enhance the interfacial bond strength and lead to structural color with high color fastness. The surface morphology of double-layer aggregates of the PDA film on structural colored cotton fabric was revealed by scanning electron microscopy. The chemical constitution of the PDA film and PVP was investigated by Fourier transform infrared spectroscopy and X-ray diffraction. The color characteristics of structural colored cotton fabrics were analyzed by UV-vis reflectance spectroscopy and spectrophotometry.

Polyvinylpyrrolidone-Aminopropyl-SBA-15 schiff Base hybrid for efficient removal of divalent heavy metal cations from wastewater

The mesoporous silica-polymer hybrid was prepared as an adsorbent for divalent heavy metals (Pb(II), Ni(II), and Cu (II)) from rice husk and polyvinylpyrrolidone (PVP) through three successive steps. The first is the preparation of the mesoporous silica (SBA-15), the second is grafting 3-aminopropyltrimethoxysilane on SBA-15, and the following step is the formation of Schiff base (PVP-SBA-15) between amine end-capped silica and PVP moieties. The materials were characterized by different techniques, including FTIR, low and wide-angle XRD, N₂-adsorption, and HR-TEM. The NH₂-SBA-15 displayed a moderate affinity toward heavy element ions under study. Grafting of PVP moieties introduces a high affinity toward heavy metal ions, and the adsorption is a well-fitted Langmuir adsorption model. A series of experiment adsorption equilibrium reported with SBA-15, NH₂-SBA-15, and PVP-SBA-15, which showed an adsorption capacity of 128 mg/g (Cu (II)), 175 mg/g (Pb (II)) and 72 mg/g for Ni(II). Kinetic studies have shown that the best way to describe the adsorption process of heavy metals is pseudo-first-order. The value of ΔG°, ΔH°, and ΔS° demonstrated that the adsorption of heavy metals on the PVP-SBA-15 was endothermic in nature and spontaneous. These results exhibited that PVP-SBA-15 material has considerable competence in eliminating heavy metals from wastewater.

Self-immobilized Pd nanowires as an excellent platform for a continuous flow reactor: efficiency, stability and regeneration

Despite extensive use of Pd nanocrystals as catalysts, the realization of a Pd-based continuous flow reactor remains a challenge. Difficulties arise due to ill-defined anchoring of the nanocrystals on a substrate and reactivity of the substrate under different reaction conditions. We demonstrate the first metal (Pd) nanowire-based catalytic flow reactor that can be used across different filtration platforms, wherein, reactants flow through a porous network of nanowires (10-1000 nm pore sizes) and the product can be collected as filtrate. Controlling the growth parameters and obtaining high aspect ratio of the nanowires (diameter = ∼13 nm and length > 8000 nm) is necessary for successful fabrication of this flow reactor. The reactor performance is similar to a conventional reactor, but without requiring energy-expensive mechanical stirring. Synchrotron-based EXAFS studies were used to examine the catalyst microstructure and Operando FT-IR spectroscopic studies were used to devise a regenerative strategy. We show that after prolonged use, the catalyst performance can be regenerated up to 99% by a simple wash-off process without disturbing the catalyst bed. Thus, collection, regeneration and redispersion processes of the catalyst in conventional industrial reactors can be avoided. Another important advantage is avoiding specific catalyst-anchoring substrates, which are not only expensive, but also non-universal in nature.

Ultralight Conductive Silver Nanowire Aerogels

Low-density metal foams have many potential applications in electronics, energy storage, catalytic supports, fuel cells, sensors, and medical devices. Here, we report a new method for fabricating ultralight, conductive silver aerogel monoliths with predictable densities using silver nanowires. Silver nanowire building blocks were prepared by polyol synthesis and purified by selective precipitation. Silver aerogels were produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to weld the nanowire junctions. As-prepared silver aerogels have unique anisotropic microporous structures, with density precisely controlled by the nanowire concentration, down to 4.8 mg/cm³ and an electrical conductivity up to 51 000 S/m. Mechanical studies show that silver nanowire aerogels exhibit "elastic stiffening" behavior with a Young's modulus up to 16 800 Pa.

The polyvinylpyrrolidone functionalized rGO/Bi2S3 nanocomposite as a near-infrared light-responsive nanovehicle for chemo-photothermal therapy of cancer

Recently, a combination of chemotherapy with photothermal therapy (PTT) has received great attention for the construction of a near infrared (NIR)-controlled drug-delivery system for synergistic treatment of cancer, ultimately resulting in the enhancement of the therapeutic efficacy of anticancer drugs. Here, we developed a novel system for synergistic cancer therapy based on bismuth sulfide (Bi2S3) nanoparticle-decorated graphene functionalized with polyvinylpyrrolidone (PVP) (named PVP-rGO/Bi2S3). The as-prepared PVP-rGO/Bi2S3 nanocomposite has a high storage capacity for anticancer drugs (∼500% for doxorubicin (DOX)) and simultaneously has perfect photothermal conversion efficiency in the NIR region. The results of the in vitro accumulative drug release test manifests that the PVP-rGO/Bi2S3 nanocomposite could be applied as a dual pH- and NIR-responsive nanotherapeutic carrier for the controlled release of DOX from DOX-loaded PVP-rGO/Bi2S3 (PVP-rGO/Bi2S3@DOX). Moreover, the treatment of both cancer cells (including Hela, MCF-7, HepG2 and BEL-7402 cells) and BEL-7402 tumor-bearing mice with the PVP-rGO/Bi2S3@DOX complex followed by NIR laser irradiation produces significantly greater inhibition of cancer cell growth than the treatment with NIR irradiation alone or DOX alone, exhibiting a synergistic antitumor effect. Furthermore, due to the obvious NIR and X-ray absorption ability, the PVP-rGO/Bi2S3 nanocomposite could be employed as a dual-modal contrast agent for both photoacoustic tomography and X-ray computed tomography imaging. In addition to the good biocompatibility, the PVP-rGO/Bi2S3 nanocomposite paves a potential way for the fabrication of theranostic agents for dual-modal imaging-guided chemo-photothermal combined cancer therapy.