Nanostructured conductive polymers have been widely researched for various applications such as energy storage and conversion, chemical/biological sensors, and biomedical devices. Recently, novel ...synthetic methods which adopt doping molecules as cross-linker have been developed to prepare conductive polymer gels (CPGs) with cross-linked network and 3D hierarchically porous nanostructures. The CPGs, as well as their derived carbon frameworks, exhibit high electrical conductivity, large surface area, structural tunability, and hierarchical porosity for rapid mass/charge transport, which contribute to their high performance when applied for energy storage and conversion devices. This Perspective highlights the key features of CPGs and their derived carbon frameworks, discusses their possibilities in terms of rational synthesis and energy-related applications, and proposes future directions for their technological development.
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IJS, KILJ, NUK, PNG, UL, UM
Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With ...rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocks into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. We hope that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.
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Polyaniline‐coated sulfur/conductive‐carbon‐black (PANI@S/C) composites with different contents of sulfur are prepared via two facile processes including ball‐milling and thermal treatment of the ...conductive carbon black and sublimed sulfur, followed by an in situ chemical oxidative polymerization of the aniline monomer in the presence of the S/C composite and ammonium persulfate. The microstructure and electrochemical performance of the as‐prepared composites are investigated systematically. It is demonstrated that the polyaniline, with a thickness of ≈5–10 nm, is coated uniformly onto the surface of the S/C composite forming a core/shell structure. The PANI@S/C composite with 43.7 wt% sulfur presents the optimum electrochemical performance, including a large reversible capacity, a good coulombic efficiency, and a high active‐sulfur utilization. The formation of the unique core/shell structure in the PANI@S/C composites is responsible for the improvement of the electrochemical performance. In particular, the high‐rate charge/discharge capability of the PANI@S/C composites is excellent due to a synergistic effect on the high electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface. Even at an ultrahigh rate (10C), a maximum discharge capacity of 635.5 mA h per g of sulfur is still retained for the PANI@S/C composite after activation, and the discharge capacity retention is over 60% after 200 cycles.
A polyaniline‐coated sulfur/conductive‐carbon‐black (PANI@S/C) composite presents an exceptional high‐rate charge/discharge capability and a high active‐sulfur utilization due to the unique core/shell structure and a synergistic effect on the electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface.
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Atmospheric water harvesting (AWH)—producing fresh water via collecting moisture from air—enables sustainable water delivery without geographical and hydrologic limitations. However, the fundamental ...design principle to prepare materials that can convert the water vapor in the air to collectible liquid water is still mostly unknown. Here, a super moisture‐absorbent gel, which is composed of hygroscopic polypyrrole chloride penetrating in hydrophilicity‐switchable polymeric network of poly N‐isopropylacrylamide, is shown. Based on such design, a high‐efficiency water production by AWH has been achieved in a broad range of relative humidity. The synergistic effect enabled by the molecular level integration of hygroscopic and hydrophilicity‐switchable polymers in a network architecture presents controllable interaction between the gel and water molecules, simultaneously realizing efficient vapor capturing, in situ water liquefaction, high‐density water storage and fast water releasing under different weather conditions. Being an effective method to regulate migration of water molecules, such design represents a novel strategy to improve the AWH, and it is also fundamental to other water management systems for environmental cooling, surficial moisturizing and beyond.
Super‐moisture‐absorbent gels that consist of functional polymers simultaneously exhibit hygroscopicity and controllable hydrophilicity. Such a gel can spontaneously capture atmospheric water, and efficiently deliver liquid water under various environmental conditions. This work not only reveals the necessity of gel‐based moisture absorbency, but also paves the way for fresh water production from air.
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Photoluminescence originated from doped activators in the solid state materials usually faces the challenge of concentration quenching, restricting the further increase of photoluminescence ...intensity. Herein, a new strategy is demonstrated by the heavy doping Mn2+ into MgAl2O4, leading to the broad‐band near‐infrared (NIR) emission peaking at ≈825 nm with a full width at half maximum of ≈125 nm, as well as high internal quantum efficiency of ≈53% upon 450 nm laser excitation. Density functional theory calculation and extend X‐ray absorption fine structure provide a understanding of Al3+/Mn2+ disorder and Mn2+–Mn2+ aggregation in spinel Mg1–xAl2O4:xMn2+ with high Mn2+ content, which enables the formation of superexchange coupled IVMn2+–VIMn2+ pair. The NIR light‐emitting diodes fabricated by the 450 nm blue chip and Mg0.50Al2O4:0.50Mn2+ phosphor gives a high NIR output power of ≈78.41 mW under a driven current of 120 mA, and night‐vision application as light source in the dark is demonstrated. This work opens new paths for rational design of efficient broad‐band NIR emitting phosphor, and also provides new insights into the Mn2+ luminescence and the applications.
A new strategy via Mn2+–Mn2+ aggregation is demonstrated by heavy doping Mn2+ into spinel MgAl2O4, enabling the formation of broad‐band near‐infrared (NIR) emission peaking at ≈825 nm with an FWHM of ≈125 nm. The NIR light‐emitting diode fabricated by this phosphor and 450 nm blue chip generates an NIR output power of ≈78.41 mW, showing high potential for night‐vision application.
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Abstract
2‐Hydroxypyridines have emerged as versatile nucleophiles in organic synthesis. The
N
‐ and
O
‐functionalization of 2‐hydroxypyridines affords straightforward and practical methods for the ...construction of
N
‐substituted 2‐pyridones and
O
‐substituted 2‐hydroxypyridines, which are important structural motifs in numerous natural products, pharmaceuticals and biologically active compounds. Nonetheless, the competition between
N
‐ and
O
‐functionalization of 2‐hydroxypyridines presents an inevitable and formidable challenge. In the past few decades, chemoselective
N
‐ and/or
O
‐functionalization of 2‐hydroxypyridines has received extensive attention from the synthetic community, resulting in the development of elegant and effective strategies to address this chemoselectivity. This review provides a summary of recent advancements in the realm of transition‐metal and organo‐catalyzed, as well as visible‐light promoted chemoselective functionalization of 2‐hydroxypyridines, including
N
‐alkylation,
N
‐allylation,
N
‐arylation,
N
‐alkenylation,
O
‐alkylation,
O
‐allylation,
O
‐arylation, and
O
‐alkenylation.
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Solar steam water purification and fog collection are two independent processes that could enable abundant fresh water generation. We developed a hydrogel membrane that contains hierarchical ...three-dimensional microstructures with high surface area that combines both functions and serves as an all-day fresh water harvester. At night, the hydrogel membrane efficiently captures fog droplets and directionally transports them to a storage vessel. During the daytime, it acts as an interfacial solar steam generator and achieves a high evaporation rate of 3.64 kg m
h
under 1 sun enabled by improved thermal/vapor flow management. With a homemade rooftop water harvesting system, this hydrogel membrane can produce fresh water with a daily yield of ~34 L m
in an outdoor test, which demonstrates its potential for global water scarcity relief.
The development of a scalable, low-cost, and versatile biosensor platform for the sensitive and rapid detection of human metabolites is of great interest for healthcare, pharmaceuticals, and medical ...science. On the basis of hierarchically nanostructured conducting polymer hydrogels, we designed a flexible biosensor platform that can detect various human metabolites, such as uric acid, cholesterol, and triglycerides. Owing to the unique features of conducting polymer hydrogels, such as high permeability to biosubstrates and rapid electron transfer, our biosensors demonstrate excellent sensing performance with a wide linear range (uric acid, 0.07–1 mM; cholesterol, 0.3–9 mM, and triglycerides, 0.2–5 mM), high sensitivity, low sensing limit, and rapid response time (∼3 s). Given the facile and scalable processability of hydrogels, the proposed conductive hydrogels-based biosensor platform shows great promise as a low-cost sensor kit for healthcare monitoring, clinical diagnostics, and biomedical devices.
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We propose an effective highest occupied d‐orbital modulation strategy engendered by breaking the coordination symmetry of sites in the atomically precise Cu nanocluster (NC) to switch the product of ...CO2 electroreduction from HCOOH/CO to higher‐valued hydrocarbons. An atomically well‐defined Cu6 NC with symmetry‐broken Cu−S2N1 active sites (named Cu6(MBD)6, MBD=2‐mercaptobenzimidazole) was designed and synthesized by a judicious choice of ligand containing both S and N coordination atoms. Different from the previously reported high HCOOH selectivity of Cu NCs with Cu−S3 sites, the Cu6(MBD)6 with Cu−S2N1 coordination structure shows a high Faradaic efficiency toward hydrocarbons of 65.5 % at −1.4 V versus the reversible hydrogen electrode (including 42.5 % CH4 and 23 % C2H4), with the hydrocarbons partial current density of −183.4 mA cm−2. Theoretical calculations reveal that the symmetry‐broken Cu−S2N1 sites can rearrange the Cu 3d orbitals with
dx2-y2
${d_{x^2 - y^2 } }$
as the highest occupied d‐orbital, thus favoring the generation of key intermediate *COOH instead of *OCHO to favor *CO formation, followed by hydrogenation and/or C−C coupling to produce hydrocarbons. This is the first attempt to regulate the coordination mode of Cu atom in Cu NCs for hydrocarbons generation, and provides new inspiration for designing atomically precise NCs for efficient CO2RR towards highly‐valued products.
Breaking the coordination symmetry of Cu site in atomically precise Cu6 cluster forms Cu‐S2N1 site, which rank the dx2‐y2 orbital as the highest occupied d orbital to favor the specific coordination between C atom of CO2 and Cu−S2N1 site. This binding mode is conductive to the generation of *COOH instead of *OCHO, thereby switching the product of electrocatalytic CO2 reduction reaction to higher‐valued hydrocarbons.
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Li2S is one of the most promising cathode materials for Li‐ion batteries because of its high theoretical capacity and compatibility with Li‐metal‐free anode materials. However, the poor conductivity ...and electrochemical reactivity lead to low initial capacity and severe capacity decay. In this communication, a nitrogen and phosphorus codoped carbon (N,P–C) framework derived from phytic acid doped polyaniline hydrogel is designed to support Li2S nanoparticles as a binder‐free cathode for Li–S battery. The porous 3D architecture of N and P codoped carbon provides continuous electron pathways and hierarchically porous channels for Li ion transport. Phosphorus doping can also suppress the shuttle effect through strong interaction between sulfur and the carbon framework, resulting in high Coulombic efficiency. Meanwhile, P doping in the carbon framework plays an important role in improving the reaction kinetics, as it may help catalyze the redox reactions of sulfur species to reduce electrochemical polarization, and enhance the ionic conductivity of Li2S. As a result, the Li2S/N,P–C composite electrode delivers a stable capacity of 700 mA h g−1 with average Coulombic efficiency of 99.4% over 100 cycles at 0.1C and an areal capacity as high as 2 mA h cm−2 at 0.5C.
Nitrogen and phosphorus codoped carbon framework with Li2S nanoparticles impregnated is designed as a high‐performance binder‐free cathode for Li–S batteries. The porous 3D architecture facilitates fast ion and electron transport to each Li2S nanoparticle, improving the utilization of active material and rate capability.
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