CdS‐Nanoparticle/Polymer Composite Shells Grown on Silica Nanospheres by Atom‐Transfer Radical Polymerization

In this paper we describe the combined use of surface‐initiated atom transfer radical polymerization (ATRP) and a gas/solid reaction in the direct preparation of CdS‐nanoparticle/block‐copolymer composite shells on silica nanospheres. The block copolymer, consisting of poly(cadmium dimethacrylate) (PCDMA) and poly(methyl methacrylate) (PMMA), is obtained by repeatedly performing the surface‐initiated ATRP procedures in N,N‐dimethylformamide (DMF) solution at room temperature, using cadmium dimethacrylate (CDMA) and methyl methacrylate (MMA) as the monomers. CdS nanoparticles with an average size of about 3 nm are generated in situ by exposing the silica nanospheres coated with block‐copolymer shells to H₂S gas. These synthetic core–shell nanospheres were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), diffuse reflectance UV‐vis spectroscopy, X‐ray photoelectron spectroscopy (XPS), and powder X‐ray diffraction (XRD). These composite nanospheres exhibit strong red photoluminescence in the solid state at room temperature.     

Preparation of High‐Performance Conductive Polymer Fibers through Morphological Control of Networks Formed by Nanofillers

A general method is described to prepare high‐performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower‐melting‐temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt‐based process. Morphological control of the conductive network formed by nanofillers is realized by solid‐state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275 S m^?1 with tensile strengths of around 500 MPa. To the best of the authors' knowledge, it is the most conductive, high‐strength polymer fiber produced by melt‐processing reported in literature, despite the fact that only ～5 wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ～0.5 wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers.     

Flexible Janus Nanoribbons Array: A New Strategy to Achieve Excellent Electrically Conductive Anisotropy,Magnetism, and Photoluminescence

A new type of flexible Janus nanoribbons array with anisotropic electrical conductivity, magnetism, and photoluminescence has been successfully fabricated by electrospinning technology using a specially designed parallel spinneret. Every single Janus nanoribbon in the array consists of a half side of Fe₃O₄ nanoparticles/polyaniline/polymethylmethacrylate (PMMA) conductive‐magnetic bifunctionality and the other half side of Tb(BA)₃phen/PMMA insulative‐photoluminescent characteristics, and all the Janus nanoribbons are aligned to form array. Owing to the unique nanostructure, the conductance along with the length direction of nanoribbons reaches up to eight orders of magnitude higher than that along with perpendicular direction, which is by far the most excellent conductive anisotropy for anisotropic conductive materials. The Janus nanoribbons array is also simultaneously endowed with magnetic and photoluminescent characteristics. The obtained Janus nanoribbons array will have important applications in the future subminiature electronic equipments owing to its high electrical anisotropy and multifunctionality. Furthermore, the design concept and fabrication technique for the flexible Janus nanoribbons array provide a new and facile approach for the preparation of anisotropic conductive films with multifunctionality.     

Optically Transparent,Ultrathin Pt Films as Versatile Metal Substrates for Molecular Optoelectronics

This contribution reports a simple, straightforward method (cool sputtering) of fabricating robust, homogeneous, conductive, and optically transparent ultrathin Pt films. Their morphological, structural, mechanical, electrical, and optical properties are reported. The morphology and structure of these Pt films are investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X‐ray diffraction. The ultrathin Pt films, approximately 20 nm thick, are characterized by a homogenous, polycrystalline structure, with a tendency to adopt a (111) texture upon the thermal treatment. Moreover, thermal treatment (annealing or flaming) of the as‐prepared films also substantially improves their chemical and mechanical robustness. F films behave as bulk Pt in terms of electrical resistivity and suitability as working electrodes in cyclic voltammetry experiments. Overall, the unique combination of these excellent features: homogeneity, robustness, and conductivity, in addition to the high optical transparency in the 300–800 nm range of the electromagnetic spectrum, make ultrathin Pt films appropriate for a variety of applications in the field of molecular optoelectronics. The formation of functional molecular self‐assembled monolayers (SAMs) on these transparent, conductive films allows their optical monitoring using transmission optical spectroscopy, as well as the probing of their electrical properties. The potential of such Pt films as suitable metal substrates in opto‐ and nanoelectronics is proven by representative applications, including switching of prototypical photochromic and electrochromic species in SAMs and molecule–metal junctions.     

Novel Percolation Mechanism in PMMA Matrix Composites Containing Segregated ITO Nanowire Networks

Poly(methyl methacrylate) (PMMA)/indium tin oxide (ITO) nanocomposites were prepared by mechanical mixing and compression molding in order to study the properties and microstructure of the composites. The composites were examined by optical and scanning electron microscopy, impedance spectroscopy, and UV‐VIS spectrophotometry. It was observed that upon compaction of the powders above the glass‐transition temperature of the matrix, the PMMA transforms from spherical to polyhedral‐shaped, and develops sharp edges and flat faces. The ITO nanoparticles do not penetrate the polymer particles, resulting in a novel segregated network microstructure. Excellent correlation between the electrical, optical, and microscopy data also provide good insight about the behavior of the filler as the content is increased in the nanocomposites. There is strong evidence that the ITO nanoparticles are extensively displaced during compaction as the PMMA powders become polyhedral‐shaped. Our results indicate that percolation occurs due to the ITO forming a continuous network along the edges of the faceted PMMA particles. The ITO nanoparticles do not appear on the faces of the PMMA particles until after a percolation path has formed and a marked increase in electrical conductivity has occurred. This behavior significantly diverges from previous models for segregated network microstructures which proposed that percolation occurred as the result of limited displacement of the filler during compaction of the mixed powders.     

Pulsed Laser Deposition and Electrochemical Characterization of LiFePO4–Ag Composite Thin Films

A simple approach is proposed to enhance the electrical conductivity of olivine‐structured LiFePO₄ thin films by uniformly dispersing small fractions of highly conductive silver (ca. 1.37 wt %) throughout the LiFePO₄ film. In this approach, a highly densified (>85 %) LiFePO₄–Ag target was first fabricated by coating conductive silver nanoparticles onto the surfaces of hydrothermally synthesized LiFePO₄ ultrafine particles by a soft chemical route. Pulsed laser deposition (PLD) was then employed to deposit LiFePO₄–Ag composite thin films on the Si/SiO₂/Ti/Pt substrates. The PLD experimental parameters were optimized to obtain well‐crystallized and olivine‐phase pure LiFePO₄–Ag composite thin films with smooth surfaces and homogeneous thicknesses. X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectrometry (Raman), X‐ray photoelectron spectroscopy (XPS), DC conductivity measurements, cyclic voltammetry(CV), as well as galvanostatic measurements were employed to characterize the as‐obtained LiFePO₄–Ag composite films. The results revealed that after silver incorporation, the olivine LiFePO₄ film cathode shows a superior electrochemical performance with a good combination of moderate specific capacity, stable cycling, and most importantly, a remarkable tolerance against high rates and over‐charging and ‐discharging.     

Monolayer-protected silver nano-particle-based anisotropic conductive adhesives: Enhancement of electrical and thermal properties

Two types of self-assembled monolayers (SAMs), dicarboxylic acid and dithiol, were used to treat the silver nanoparticles. Thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), and contact angle results indicated that the SAMs were well coated on the silver nanoparticles and thermally stable below 150°C. By introducing the monolayer-coated silver nanoparticles into the anisotropic conductive adhesives (ACAs), the electrical properties and thermal conductivity of ACAs were significantly improved. The joint resistance of the ACA decreased from 10⁻³ Ohm to 10⁻⁵ Ohm with SAMs-coated silver fillers, and the current carrying capability of ACAs was also obviously improved. The improved electrical properties are due to the stronger bonding between nanofillers and the SAM coating materials; consequently, this improved the ACA interfacial properties. The enhanced interfacial properties with the SAM-protected nanofillers also attributed to the improved thermal conductivity of ACAs.     

Highly Stretchable Conductors Integrated with a Conductive Carbon Nanotube/Graphene Network and 3D Porous Poly(dimethylsiloxane)

Here, a novel and facile method is reported for manufacturing a new stretchable conductive material that integrates a hybrid three dimensional (3D) carbon nanotube (CNT)/reduced graphene oxide (rGO) network with a porous poly(dimethylsiloxane) (p‐PDMS) elastomer (pPCG). This reciprocal architecture not only alleviates the aggregation of carbon nanofillers but also significantly improves the conductivity of pPCG under large strains. Consequently, the pPCG exhibits high electrical conductivity with a low nanofiller loading (27 S m^?1 with 2 wt% CNTs/graphene) and a notable retention capability after bending and stretching. The simulation of the mechanical properties of the p‐PDMS model demonstrates that an extremely large applied strain (ε_appl) can be accommodated through local rotations and bending of cell walls. Thus, after a slight decrease, the conductivity of pPCG can continue to remain constant even as the strain increases to 50%. In general, this architecture of pPCG with a combination of a porous polymer substrate and 3D carbon nanofiller network possesses considerable potential for numerous applications in next‐generation stretchable electronics.     

A Facile In Situ Approach to Polypyrrole Functionalization Through Bioinspired Catechols

A template‐free benign approach to modify polypyrrole (PPy) with bioinspired catechol derivatives dopamine (DA), 1,2‐dihydroxybenzene or catechol (CA), and l ‐3,4‐dihydroxyphenylalanine (DOPA) is reported. It is found that PPy functionalized with these catechol derivatives (DA, CA, and DOPA) exhibited fibrous structure, smaller particle size, good water dispersibility, and enhanced film adhesion. Surprisingly, it is found that adding a small amount of catechols can also improve PPy's electrical conductivity. This rapid, one‐step, in situ, template‐free method provided an alternative strategy to the facile production of PPy fibers. Among these three catechols, functionalized PPy and DA‐PPy exhibits the smallest particle size and best performance in both adhesion and electrical conductivity. In contrast, the control phenylethlamine (PA) modification had almost negligible influence on the PPy properties, which provides strong evidence that instead of amine functional group or coexistence of both catechol and amine moieties, catechol itself is responsible for the successful functionalization of PPy and overall performance improvement. Furthermore, catechol‐PPy nanofibers are blended into polyvinyl alcohol (PVA) aqueous solution and casted to form thin films; as‐synthesized conductive films are found able to bond strongly onto the surface and may find broad applications in manufacturing biosensors and electronic devices.     

Luminescent Core/Shell Nanoparticles with a Rhabdophane LnPO4‐xH2O Structure: Stabilization of Ce3+‐Doped Compositions

The core/shell strategy has been successfully developed for rhabdophane lanthanide phosphate aqueous colloids. The growth of a LaPO₄‐xH₂O shell around Ce,Tb‐doped core nanoparticles increases their stability against oxidation. A bright green luminescence is thus preserved in sol–gel films whose fabrication requires silica coating and thermal treatment of the core/shell nanoparticles.     

Nanoporous Ultra‐Low‐Dielectric‐Constant Fluoropolymer Films via Selective UV Decomposition of Poly(pentafluorostyrene)‐block‐Poly(methyl methacrylate) Copolymers Prepared Using Atom Transfer Radical Polymerization

Block copolymers of poly(pentafluorostyrene) (PFS) and poly(methyl methacrylate) (PMMA) (PFS‐b‐PMMA) have been synthesized using atom transfer radical polymerization (ATRP). Then, nanoporous fluoropolymer films have been prepared via selective UV decomposition of the PMMA blocks in the PFS‐b‐PMMA copolymer films. The chemical composition and structure of the PFS homopolymers and copolymers have been characterized using nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS), and molecular‐weight measurements. The cross‐sectional and surface morphologies of the PFS‐b‐PMMA copolymer films before and after selective UV decomposition of the PMMA blocks have been studied using field‐emission scanning electron microscopy (FESEM). The nanoporous fluoropolymer films with pore sizes in the range 30–50 nm and porosity in the range 15–40 % have been obtained from the PFS‐b‐PMMA copolymers of different PMMA content. Dielectric constants approaching 1.8 have been achieved in the nanoporous fluoropolymer films which contain almost completely decomposed PMMA blocks.     

A Novel Conductive Core–Shell Particle Based on Liquid Metal for Fabricating Real‐Time Self‐Repairing Flexible Circuits

As a critical part of flexible electronics, flexible circuits inevitably work in a dynamic state, which causes electrical deterioration of brittle conductive materials (i.e., Cu, Ag, ITO). Recently, gallium‐based liquid metal particles (LMPs) with electrical stability and self‐repairing have been studied to replace brittle materials owing to their low modulus and excellent conductivity. However, LMP‐coated Ga₂O₃ needs to activate by external sintering, which makes it more complicated to fabricate and gives it a larger short‐circuit risk. Core–shell structural particles (Ag@LMPs) that exhibit excellent initial conductivity(8.0 Ω sq^?1) without extra sintering are successfully prepared by coating nanosilver on the surface of LMPs through in situ chemical reduction. The critical stress at which rigid Ag shells rupture can be controlled by adjusting the Ag shell thickness so that LM cores with low moduli can release, achieving real‐time self‐repairing (within 200 ms) under external destruction. Furthermore, a flexible circuit utilizing Ag@LMPs is fabricated by screen printing, and exhibits outstanding stability and durability (R/R₀ < 1.65 after 10 000 bending cycles in a radius of 0.5 mm) because of the functional core–shell structure. The self‐repairable Ag@LMPs prepared in this study are a candidate filler for flexible circuit design through multiple processing methods.     

Photopatternable Conductive PDMS Materials for Microfabrication

Conductive photodefinable polydimethylsiloxane (PDMS) composites that provide both high electrical conductivity and photopatternability have been developed. The photosensitive composite materials, which consist of a photosensitive component, a conductive filler, and a PDMS pre‐polymer, can be used as a negative photoresist or a positive photoresist with an additional curing agent. A standard photolithographic approach has been used to fabricate conductive elastomeric microstructures. Feature sizes of 60 µm in the positive photoresist and 10 µm in the negative photoresist have been successfully achieved. Moreover, as the conductive filler, silver powders significantly improve the electrical conductivity of the PDMS polymer, but also provide enhanced mechanical and thermal properties as well as interesting biological properties. The combined electrical, mechanical, thermal, and biological properties along with photopatternability make the PDMS‐Ag composite an excellent processable and structural material for various microfabrication applications.     

Yolk–Shell Structured FeP@C Nanoboxes as Advanced Anode Materials for Rechargeable Lithium‐/Potassium‐Ion Batteries

Maintaining structural stability and alleviating the intrinsic poor conductivity of conversion‐type reaction anode materials are of great importance for practical application. Introducing void space and a highly conductive host to accommodate the volume changes and enhance the conductivity would be a smart design to achieve robust construction; effective electron and ion transportation, thus, lead to prolonged cycling life and excellent rate performance. Herein, uniform yolk–shell FeP@C nanoboxes (FeP@CNBs) with the inner FeP nanoparticles completely protected by a thin and self‐supported carbon shell are synthesized through a phosphidation process with yolk–shell Fe₂O₃@CNBs as a precursor. The volumetric variation of the inner FeP nanoparticles during cycling is alleviated, and the FeP nanoparticles can expand without deforming the carbon shell, thanks to the internal void space of the unique yolk–shell structure, thus preserving the electrode microstructure. Furthermore, the presence of the highly conductive carbon shell enhances the conductivity of the whole electrode. Benefiting from the unique design of the yolk–shell structure, the FeP@CNBs manifests remarkable lithium/potassium storage performance.     

Preparation of Hollow Silica Nanospheres by Surface‐Initiated Atom Transfer Radical Polymerization on Polymer Latex Templates

Poly(vinylbenzyl chloride), (PVBC) latex particles of about 100 nm in size are prepared by emulsion polymerization. Silyl functional groups are introduced onto the PVBC‐nanoparticle templates via surface‐initiated atom transfer radical polymerization of 3‐(trimethoxysilyl)propyl methacrylate. The silyl groups are then converted into a silica shell, approximately 20 nm thick, via a reaction with tetraethoxysilane in ethanolic ammonia. Hollow silica nanospheres are finally generated by thermal decomposition of the PVBC template cores. Field‐emission scanning electron microscopy and field‐emission transmission electron microscopy are used to characterize the intermediate products and the hollow nanospheres. Fourier‐transform infrared spectroscopy results indicate that the polymer cores are completely decomposed.     

Fabrication of flexible conductive graphene/Ag/Al-doped zinc oxide multilayer films for application in flexible organic light-emitting diodes

Graphene/Ag/Al-doped zinc oxide (AZO) multilayer films were fabricated by using chemical vapor deposition and magnetron sputtering methods. The electrical and optical properties of the transparent conductive graphene/Ag/AZO films were investigated. The graphene/Ag/AZO film can maintain high conductivity and transmittance without obvious degradation during bending test. A green flexible organic light emitting diode with a structure of graphene/Ag/AZO/N,N-diphenyl-N,N-bis(1-napthyl)-1,1-biphenyl-4,4-diamine/tris(8-hydroxyquinoline) aluminum(III)/lithium fluoride/Al exhibited a stable green emission and light-emitting efficiency during the cycle bending test. The multilayer films hold promise for application in flexible optoelectronic devices.     

Conductive polypyrrole–bacterial cellulose nanocomposite membranes as flexible supercapacitor electrode

Conductive nanocomposite membranes of polypyrrole/bacterial cellulose (PPy/BC) were fabricated in situ by oxidative polymerization of pyrrole with iron (III) chloride as an oxidant and BC as a template. The morphology of the PPy/BC membrane indicated that PPy nanoparticles deposited on the BC surface connected to form a continuous nanosheath structure by taking along the BC nanofiber. The flexible PPy/BC membrane obtained with the optimized reaction condition exhibited a high electrical conductivity of 3.9 S cm⁻¹, which was hardly affected by bending stress. The PPy/BC membrane could be directly used as flexible supercapacitor electrodes, with a maximum discharge capacity of 101.9 mA h g⁻¹ (459.5 F g⁻¹) at 0.16 A g⁻¹ current density. The capacity decreased with charge/discharge cycling, which is attributed to mechanical degradation of PPy as evidenced by scanning electron microscopy (SEM).     

Fabrication,Characterization, and Printing of Conductive Ink Based on Multi Core–Shell Nanoparticles Synthesized by RAPET

In the current research, conductive patterns are deposited on different substrates by direct inkjet printing of conductive inks based on metal@carbon and bimetal@carbon core–shell nanoparticles synthesized by the RAPET (reaction under autogenic pressure at elevated temperatures) technique. Various co‐solvents and additives are examined for production of stable conductive ink. The morphology of the deposited layers is characterized by optical and scanning electron microscopy measurements. The stability of the prepared inks is examined by dynamic light scattering measurements. The electrical resistivity is measured by a four‐point probe system and calculated using the geometric dimensions. The results obtained are very promising and indicate that the conductivity of the deposited layers is close to that of bulk metals and higher than most results published so far. Moreover, the importance and advantages of the protective carbon layer that prevents metal oxidation is demonstrated.     

Conductive SU8 Photoresist for Microfabrication

A conductive composite photoresist has been developed for the direct photopatterning of electrodes. It is based on a dispersion of silver nanoparticles in SU8, a non‐conductive, negative‐tone photoresist. Manufactured structures have an electrical conductivity at a low silver content of around 6 vol.‐%.     

One‐Pot Preparation of Conducting Polymer‐Coated Silica Particles: Model Highly Absorbing Aerosols

Near‐monodisperse 0.50 μm and 1.0 μm silica particles are surface‐modified using 3‐(trimethoxysilyl)propyl methacrylate (MPS) and subsequently coated by aqueous deposition of an ultrathin polypyrrole (PPy) overlayer to produce PPy‐coated silica particles. The targeted degree of MPS modification and PPy mass loading are systematically varied to optimize the colloidal stability and PPy coating uniformity. MPS surface modification is characterized by contact angle goniometry and the PPy overlayer uniformity is assessed by scanning electron microscopy. HF etching of the silica cores produces hollow PPy shells, thus confirming the contiguous nature of the PPy overlayer and the core–shell morphology of the original particles. Four‐point probe measurements and XPS studies indicate that the electrical conductivity of pressed pellets of PPy‐coated silica particles increases with PPy surface coverage. Colloidal stabilities of the bare, MPS‐modified, and PPy‐coated silica particles in aqueous solution are assessed using disk centrifuge photosedimentometry. MPS surface modification results in weak flocculation, with subsequent PPy deposition causing further aggregation. In contrast, white light aerosol spectrometry indicates a relatively high degree of dispersion for PPy‐coated silica particles in the gas phase. Such PPy‐coated silica particles are expected to be useful mimics for silica‐rich micrometeorites and may also serve as a model highly absorbing aerosol.