Ultrathin Polypyrrole Nanosheets via Space-Confined Synthesis for Efficient Photothermal Therapy in the Second Near-Infrared Window

Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650–950 nm). However, PTAs for photothermal therapy in the second NIR window (1000–1350 nm) are still rare. Here, it is shown that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g^–1 cm^–1 at 1064 nm and can be used as an efficient PTA in the second NIR window. This unique optical property is attributed to the formation of bipolaron bands in highly doped PPy nanosheets. The measured prominent photothermal conversion efficiency could achieve 64.6%, surpassing previous PTAs that are active in the second NIR window. Both in vitro and in vivo studies reveal that these ultrathin PPy nanosheets possess good biocompatibility and notable tumor ablation ability in the second NIR window. Our study highlights the potential of ultrathin two-dimensional polymers with unique optical properties in biomedical applications

Photodegradable Coordination Polymer Particles for Light-Controlled Cargo Release

Stimuli-responsive coordination polymer particles (CPPs) show great promise for encapsulating and releasing cargos due to their unique and highly tailorable structures and properties. In particular, photoresponsive CPPs have received enormous interest, as noninvasive light can be spatially and temporally controlled, resulting in great safety and efficiency. In this work, we report the design and synthesis of novel photodegradable CPPs by infinite coordination polymerization of Zn²⁺ and a photocleavable organic linker containing <i>o</i>-nitrobenzyl derivatives. We further demonstrate that these novel photodegradable CPPs are able to efficiently encapsulate cargos and are applicable for on-command drug release upon low-power UV light irradiation (5.78 mW/cm²). Because light is a highly desirable remote-trigger and can be used externally, we expect that these photodegradable CPPs can provide a unique platform for controlled cargo release

Mechanical Activation of Platinum–Acetylide Complex for Olefin Hydrosilylation

Harnessing mechanical forces to activate latent catalysts has emerged as a novel approach to control the catalytic reactions in organic syntheses and polymerization processes. However, using polymer mechanochemistry to activate platinum-based catalysts, a class of important organometallic catalysts in industry, has not been demonstrated so far. Here we show that the platinum–acetylide complex is mechanoresponsive and can be incorporated into a polymer backbone to form a new mechanophore. The mechanically induced chain scission was demonstrated to be able to release catalytically active platinum species which could catalyze the olefin hydrosilylation process. Various control experiments were conducted to confirm that the chain scission and catalytic reaction were originated from the ultrasound-induced dissociation of platinum–acetylide complex. This work further exemplifies the utilization of organometallic complexes in design and synthesis of latent catalysts for mechanocatalysis and development of self-healing materials based on silicone polymers

Carbon Microspheres as Supercapacitors

Carbon microstructures fabricated by ultrasonic spray pyrolysis (USP) of aqueous precursors were tested as supercapacitors. USP carbons (USP-C) possess unique physicochemical characteristics, including substantial microporosity and high surface concentrations of oxygenated functional groups. We find that USP-Cs have higher electrochemical double-layer capacitance compared with other carbon structures. Porous carbon microspheres prepared from USP of lithium dichloroacetate, lithium/potassium propiolate, or sucrose produce electrochemical double layer capacitors (EDLCs) that have gravimetric capacitances of 185, 341, and 360 F/g, respectively. Microstructural and chemical analyses of the carbon materials suggest that the observed capacitance is related to the effects of surface functionality

Co Nanoparticles Encapsulated in N‑Doped Carbon Nanosheets: Enhancing Oxygen Reduction Catalysis without Metal–Nitrogen Bonding

It is known that introducing metal nanoparticles (e.g., Fe and Co) into N-doped carbons can enhance the activity of N-doped carbons toward the oxygen reduction reaction (ORR). However, introducing metals into N-doped carbons inevitably causes the formation of multiple active sites. Thus, it is challenging to identify the active sites and unravel mechanisms responsible for enhanced ORR activity. Herein, by developing a new N-heterocyclic carbene (NHC)–Co complex as the nitrogen- and metal-containing precursor, we report the synthesis of N-doped carbon nanosheets embedded with Co nanoparticles as highly active ORR catalysts without direct metal–nitrogen bonding. Electrochemical measurements and X-ray absorption spectroscopy indicate that the carbon–nitrogen sites surrounding Co nanoparticles are responsible for the observed ORR activity and stability. Density functional theory calculations further reveal that Co nanoparticles could facilitate the protonation of O₂ and thus promote the ORR activity. These results provide new prospects in the rational design and synthesis of heteroatom-doped carbon materials as non-precious-metal catalysts for various electrochemical reactions

Synthesis and Characterization of Nanostructured Copolymer-Grafted Multiwalled Carbon Nanotube Composite Thermoplastic Elastomers toward Unique Morphology and Strongly Enhanced Mechanical Properties

Considering that multiwalled carbon nanotubes (MWCNTs) can be used as anisotropic and stiff nano-objects acting as minority physical cross-linking points dispersed in soft polymer grafting matrixes, a series of copolymer-grafted multiwalled carbon nanotube composite thermoplastic elastomers (CTPEs), MWCNT-<i>graft</i>-poly­(<i>n</i>-butyl acrylate-<i>co</i>-methyl methacrylate) [MWCNT-<i>g</i>-P­(BA-<i>co</i>-MMA)], with minor MWCNT contents of 1.2–3.8 wt % was synthesized by the surface-initiated activators regenerated by electron transfer for atom-transfer radical polymerization (ARGET ATRP) method. Excellent dispersion of the MWCNTs in the CTPEs was demonstrated by SEM and TEM, and the thermal stability properties and glass transition temperatures of the CTPEs were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Mechanical property test results demonstrated that the CTPEs exhibit obviously enhanced mechanical properties, such as higher tensile strength and elastic recovery, as compared with their linear P­(BA-<i>co</i>-MMA) copolymer counterparts. The microstructural evolutions in the CTPEs during tensile deformation as investigated by in situ small-angle X-ray scattering (SAXS) revealed the role of the MWCNTs, which can provide additional cross-linking points and transform soft elastomers into strong ones

Nitrogen-Doped Hollow Carbon Nanospheres for High-Performance Li-Ion Batteries

N-doped carbon materials is of particular attraction for anodes of lithium-ion batteries (LIBs) because of their high surface areas, superior electrical conductivity, and excellent mechanical strength, which can store energy by adsorption/desorption of Li⁺ at the interfaces between the electrolyte and electrode. By directly carbonization of zeolitic imidazolate framework-8 nanospheres synthesized by an emulsion-based interfacial reaction, we obtained N-doped hollow carbon nanospheres with tunable shell thickness (20 nm to solid sphere) and different N dopant concentrations (3.9 to 21.7 at %). The optimized anode material possessed a shell thickness of 20 nm and contained 16.6 at % N dopants that were predominately pyridinic and pyrrolic. The anode delivered a specific capacity of 2053 mA h g^–1 at 100 mA g^–1 and 879 mA h g^–1 at 5 A g^–1 for 1000 cycles, implying a superior cycling stability. The improved electrochemical performance can be ascribed to (1) the Li⁺ adsorption dominated energy storage mechanism prevents the volume change of the electrode materials, (2) the hollow nanostructure assembled by the nanometer-sized primary particles prevents the agglomeration of the nanoparticles and favors for Li⁺ diffusion, (3) the optimized N dopant concentration and configuration facilitate the adsorption of Li⁺; and (4) the graphitic carbon nanostructure ensures a good electrical conductivity

Controlled Intercalation and Chemical Exfoliation of Layered Metal–Organic Frameworks Using a Chemically Labile Intercalating Agent

Creating ordered two-dimensional (2D) metal–organic framework (MOF) nanosheets has attracted extensive interest. However, it still remains a great challenge to synthesize ultrathin 2D MOF nanosheets with controlled thickness in high yields. In this work, we demonstrate a novel intercalation and chemical exfoliation approach to obtain MOF nanosheets from intrinsically layered MOF crystals. This approach involves two steps: first, layered porphyrinic MOF crystals are intercalated with 4,4′-dipyridyl disulfide through coordination bonding with the metal nodes; subsequently, selective cleavage of the disulfide bond induces exfoliation of the intercalated MOF crystals, leading to individual freestanding MOF nanosheets. This chemical exfoliation process can proceed efficiently at room temperature to produce ultrathin (∼1 nm) 2D MOF nanosheets in ∼57% overall yield. The obtained ultrathin nanosheets exhibit efficient and far superior heterogeneous photocatalysis performance compared with the corresponding bulk MOF

Hollow Metal–Organic Framework Nanospheres via Emulsion-Based Interfacial Synthesis and Their Application in Size-Selective Catalysis

Metal–organic frameworks (MOFs) represent an emerging class of crystalline materials with well-defined pore structures and hold great potentials in a wide range of important applications. The functionality of MOFs can be further extended by integration with other functional materials, e.g., encapsulating metal nanoparticles, to form hybrid materials with novel properties. In spite of various synthetic approaches that have been developed recently, a facile method to prepare hierarchical hollow MOF nanostructures still remains a challenge. Here we describe a facile emulsion-based interfacial reaction method for the large-scale synthesis of hollow zeolitic imidazolate framework 8 (ZIF-8) nanospheres with controllable shell thickness. We further demonstrate that functional metal nanoparticles such as Pd nanocubes can be encapsulated during the emulsification process and used for heterogeneous catalysis. The inherently porous structure of ZIF-8 shells enables encapsulated catalysts to show size-selective hydrogenation reactions