Enhanced thermoelectric metrics in ultra-long electrodeposited PEDOT nanowires

Robust Long-Nanowire Fabrication by Clean-Phase-Assisted Micro Chemical Pen for Enhanced Bioassay Sensitivity

Long nanowires offer an increased surface area for biomolecule immobilization, facilitating enhanced binding capacity and sensitivity in the detection of target analytes. However, robust long-nanowire fabrication remains a significant challenge. In this paper, we developed a novel construction of a micro chemical pen (MCP), called a clean-assisted micro chemical pen (CAMCP), for robust long-nanowire fabrication. CAMCP, based on localized hydrodynamic flow confinement, was conducted by incorporating a clean phase to effectively dissolve aggregated silver particles in the aspiration channel's shell, thereby enhancing the MCP's longevity by 60.84%, allowing for an 840 μm extension in nanowire patterning capability. A 4600-aspect ratio (length:1200 μm, width: 260 nm) nanowire was fabricated by CAMCP and utilized as a nanowire sensor, showing a 39.7% increase in IgA detection sensitivity compared to a 3000-aspect ratio sensor. Furthermore, the longer nanowire sensor exhibited enhanced signal responses, a higher signal-to-noise ratio, and a lower limit of detection (LOD). The preponderant bioassay performances of the longer nanowire sensor in bioassays, facilitated by CAMCP, open up its possibilities for chemical-synthesis nanowires (NWs) in ultrasensitive biodetection.

Chirality-enhanced 2D conductive polymer for flexible electronics and chiral sensing applications

Chiral two-dimensional (2D) conductive polymers, encompassing chiral, 2D, flexible, and conductive properties, constitute a novel class of material that remains largely unexplored. The infusion of chirality into 2D conductive polymers taps into the unique characteristics associated with chirality, presenting opportunities to enhance or tailor the electronic, optical, and structural properties of materials for specific technological applications. In this study, we synthesized a chiral 2D PEDOT:PMo11V nanofilm through interfacial polymerization, effectively integrating a chiral monolayer, conductive polymer, and inorganic cluster. The inclusion of inorganic cluster serves to enhance the conductivity of the resulting chiral nanofilm. Furthermore, we demonstrated the chiral nanofilm as a capable electrochemical sensor for detecting drug enantiomers. The inherent flexibility of the chiral nanofilm also lays the groundwork for the development of chiral flexible/wearable devices.

Advancing Thermoelectric Materials: A Comprehensive Review Exploring the Significance of One-Dimensional Nano Structuring

Amidst the global challenges posed by pollution, escalating energy expenses, and the imminent threat of global warming, the pursuit of sustainable energy solutions has become increasingly imperative. Thermoelectricity, a promising form of green energy, can harness waste heat and directly convert it into electricity. This technology has captivated attention for centuries due to its environmentally friendly characteristics, mechanical stability, versatility in size and substrate, and absence of moving components. Its applications span diverse domains, encompassing heat recovery, cooling, sensing, and operating at low and high temperatures. However, developing thermoelectric materials with high-performance efficiency faces obstacles such as high cost, toxicity, and reliance on rare-earth elements. To address these challenges, this comprehensive review encompasses pivotal aspects of thermoelectricity, including its historical context, fundamental operating principles, cutting-edge materials, and innovative strategies. In particular, the potential of one-dimensional nanostructuring is explored as a promising avenue for advancing thermoelectric technology. The concept of one-dimensional nanostructuring is extensively examined, encompassing various configurations and their impact on the thermoelectric properties of materials. The profound influence of one-dimensional nanostructuring on thermoelectric parameters is also thoroughly discussed. The review also provides a comprehensive overview of large-scale synthesis methods for one-dimensional thermoelectric materials, delving into the measurement of thermoelectric properties specific to such materials. Finally, the review concludes by outlining prospects and identifying potential directions for further advancements in the field.

The Thermoelectric Properties of Spongy PEDOT Films and 3D-Nanonetworks by Electropolymerization

Recently, polymers have been attracted great attention because of their thermoelectric materials' excellent mechanical properties, specifically their cost-effectiveness and scalability at the industrial level. In this study, the electropolymerization conditions (applied potential and deposition time) of PEDOT films were investigated to improve their thermoelectric properties. The morphology and Raman spectroscopy of the PEDOT films were analyzed according to their applied potential and deposition time. The best thermoelectric properties were found in films grown at 1.3 V for 10 min, with an electrical conductivity of 158 ± 8 S/cm, a Seebeck coefficient of 33 ± 1 µV/K, and a power factor of 17 ± 2 µW/K·m². This power factor value is three times higher than the value reported in the literature for electropolymerized PEDOT films in acetonitrile using lithium perchlorate as a counter-ion. The thermal conductivity was found to be (1.3 ± 0.3) × 10^-1 W/m·K. The highest figure of merit obtained at room temperature was (3.9 ± 1.0) × 10^-2 using lithium perchlorate as a counter-ion. In addition, three-dimensional (3D) PEDOT nanonetworks were electropolymerized inside 3D anodic aluminum oxide (3D AAO), obtaining lower values in their thermoelectric properties.

The cross-interface energy-filtering effect at organic/inorganic interfaces balances the trade-off between thermopower and conductivity

The energy-filtering effect has been widely employed to elucidate the enhanced thermoelectric properties of organic/inorganic hybrids. However, the traditional Mott criterion cannot identify the energy-filtering effect of organic/inorganic hybrids due to the limitations of the Hall effect measurement in determining their carrier concentration. In this work, a carrier concentration-independent strategy under the theoretical framework of the Kang-Snyder model is proposed and demonstrated using PANI/MWCNT composites. The result indicates that the energy-filtering effect is triggered on increasing the temperature to 220 K. The energy-filtering effect gives a symmetry-breaking characteristic to the density of states of the charge carriers and leads to a higher thermopower of PANI/MWCNT than that of each constituent. From a morphological perspective, a paracrystalline PANI layer with a thickness of 3 nm is spontaneously assembled on the MWCNT network and serves as a metallic percolation pathway for carriers, resulting in a 5.56-fold increase in conductivity. The cooperative 3D carrier transport mode, including the 1D metallic transport along the paracrystalline PANI and the 2D cross-interface energy-filtering transport, co-determines a 4-fold increase in the power factors of PANI/MWCNT at 300 K. This work provides a physical insight into the improvement of the thermoelectric performance of organic/inorganic hybrids via the energy-filtering effect.

Long- and Short-Term Conductance Control of Artificial Polymer Wire Synapses

Networks in the human brain are extremely complex and sophisticated. The abstract model of the human brain has been used in software development, specifically in artificial intelligence. Despite the remarkable outcomes achieved using artificial intelligence, the approach consumes a huge amount of computational resources. A possible solution to this issue is the development of processing circuits that physically resemble an artificial brain, which can offer low-energy loss and high-speed processing. This study demonstrated the synaptic functions of conductive polymer wires linking arbitrary electrodes in solution. By controlling the conductance of the wires, synaptic functions such as long-term potentiation and short-term plasticity were achieved, which are similar to the manner in which a synapse changes the strength of its connections. This novel organic artificial synapse can be used to construct information-processing circuits by wiring from scratch and learning efficiently in response to external stimuli.

Viruses Masquerading as Antibodies in Biosensors: The Development of the Virus BioResistor

The 2018 Nobel Prize in Chemistry recognized in vitro evolution, including the development by George Smith and Gregory Winter of phage display, a technology for engineering the functional capabilities of antibodies into viruses. Such bacteriophages solve inherent problems with antibodies, including their high cost, thermal lability, and propensity to aggregate. While phage display accelerated the discovery of peptide and protein motifs for recognition and binding to proteins in a variety of applications, the development of biosensors using intact phage particles was largely unexplored in the early 2000s. Virus particles, 16.5 MDa in size and assembled from thousands of proteins, could not simply be substituted for antibodies in any existing biosensor architectures.Incorporating viruses into biosensors required us to answer several questions: What process will allow the incorporation of viruses into a functional bioaffinity layer? How can the binding of a protein disease marker to a virus particle be electrically transduced to produce a signal? Will the variable salt concentration of a bodily fluid interfere with electrical transduction? A completely new biosensor architecture and a new scheme for electrical transduction of the binding of molecules to viruses were required.This Account describes the highlights of a research program launched in 2006 that answered these questions. These efforts culminated in 2018 in the invention of a biosensor specifically designed to interface with virus particles: the Virus BioResistor (VBR). The VBR is a resistor consisting of a conductive polymer matrix in which M13 virus particles are entrained. The electrical impedance of this resistor, measured across 4 orders of magnitude in frequency, simultaneously measures the concentration of a target protein and the ionic conductivity of the medium in which the resistor is immersed. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise ratio (S/N > 100) and excellent sensor-to-sensor reproducibility. Using this new device, we have measured the urinary bladder cancer biomarker nucleic acid deglycase (DJ-1) in urine samples. This optimized VBR is characterized by extremely low sensor-to-sensor coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a limit of quantitation of 30 pM, encompassing 4 orders of magnitude in concentration.

Electrochemical Synthesis of an Organic Thermoelectric Power Generator

Energy harvesting through residual heat is considered one of the most promising ways to power wearable devices. In this work, thermoelectric textiles were prepared by coating the fabrics, first with multiple-wall carbon nanotubes (MWCNTs) by using the layer-by-layer technique and second with poly(3,4-ethylenedioxythiophene) (PEDOT) deposited by electrochemical polymerization. Sodium deoxycholate and poly(diallyldimethylammonium chloride) were used as stabilizers to prepare the aqueous dispersions of MWCNTs. The electrochemical deposition of PEDOT on the MWCNT-coated fabric was carried out in a three-electrode electrochemical cell. The polymerization of PEDOT on the fabric increased the electrical conductivity by ten orders of magnitude (through the plane), establishing an excellent path for electric transport across the fabrics. In addition, the fibers showed a Seebeck coefficient of 14.3 μV K^-1, which is characteristic of highly doped PEDOT. As a proof of concept, several thermoelectric modules were made with different elements based on the coated acrylic and cotton fabrics. The best generator made of 30 thermoelectric elements using acrylic fabrics exhibited an output power of 0.9 μW with a temperature difference of 31 K.

Electrochemical Synthesis of Poly(3,4-ethylenedioxythiophene) Film Having Dot Structures for Diffraction Grating

Poly(3,4-ethylenedioxythiophene) (PEDOT) dot micro/nanostructures are synthesized by electrochemical polymerization in a concentrated hydroxypropyl cellulose (HPC) liquid crystal electrolyte solution. Surface observations by scanning electron microscopy and atomic force microscopy reveal micro/nanostructures having hemisphere-like dots on the surface of the PEDOT film, which causes light diffraction at ultraviolet and visible light wavelengths. The size of the dots depends on the concentration of the HPC electrolyte solution, decreasing with increasing the HPC concentration. Electrochemical oxidation and reduction causes changes in the color of the PEDOT film and the diffracted light. Moreover, Au coating on the surface of the PEDOT film enhances the diffracted light reflection intensity by more than tenfold compared to the noncoated PEDOT film.

Ink Processing for Thermoelectric Materials and Power-Generating Devices

The growing concern over the depletion of hydrocarbon resources, and the adverse environmental effects associated with their use, has increased the demand for renewable energy sources. Thermoelectric (TE) power generation from waste heat has emerged as a renewable energy source that does not generate any pollutants. Recently, ink-based processing for the preparation of TE materials has attracted tremendous attention because of the simplicity in design of power generators and the possibility of cost-effective manufacturing. In this progress report, recent advances in the development of TE inks, processing techniques, and ink-fabricated devices are reviewed. A summary of typical formulations of TE materials as inks is included, as well as a discussion on various ink-based fabrication methods, with several examples of newly designed devices fabricated using these techniques. Finally, the prospects of this field with respect to the industrialization of TE power generation technology are presented.

Improvement of the Photoelectrochemical Performance of TiO2 Nanorod Array by PEDOT and Oxygen Vacancy Co-Modification

In this study, oxygen vacancy modified TiO2 nanorod array photoelectrode was prepared by reducing hydrogen atmosphere to increase its free charge carrier density. Subsequently, a p-type conductive poly 3,4-ethylenedioxythiophene (PEDOT) layer was deposited on the surface of oxygen vacancy modified TiO2, to inhibit the surface states. Meanwhile, a p-n heterojunction formed between PEDOT and TiO2 to improve the separation of photo-induced carriers further. The photocurrent of TiO2 nanorod array increased to nearly 0.9 mA/cm2 after the co-modification under standard sunlight illumination, whose value is nearly nine times higher than that of pure TiO2 nanorod array. Thus, this is a promising modification method for TiO2 photoanode photoelectrochemical (PEC) performance improving.

Solution-Based Synthesis and Processing of Metal Chalcogenides for Thermoelectric Applications

Metal chalcogenide materials are current mainstream thermoelectric materials with high conversion efficiency. This review provides an overview of the scalable solution-based methods for controllable synthesis of various nanostructured and thin-film metal chalcogenides, as well as their properties for thermoelectric applications. Furthermore, the state-of-art ink-based processing method for fabrication of thermoelectric generators based on metal chalcogenides is briefly introduced. Finally, the perspective on this field with regard to material production and device development is also commented upon.

One-Dimensional Nanostructure Engineering of Conducting Polymers for Thermoelectric Applications

The past few decades have witnessed considerable progress of conducting polymer-based organic thermoelectric materials due to their significant advantages over the traditional inorganic materials. The nanostructure engineering and performance investigation of these conducting polymers for thermoelectric applications have received considerable interest but have not been well documented. This review gives an outline of the synthesis of various one-dimensional (1D) structured conducting polymers as well as the strategies for hybridization with other nanomaterials or polymers. The thermoelectric performance enhancement of these materials in association with the unique morphologies and structures are discussed. Finally, perspectives and suggestions for the future research based on these interesting nanostructuring methodologies for improvement of thermoelectric materials are also presented.

Roles of Polyethylenimine Ethoxylated in Efficiently Tuning the Thermoelectric Performance of Poly(3,4-ethylenedioxythiophene)-Rich Nanocrystal Films

The regulation of oxidation levels is of great importance as an efficient way to optimize the thermoelectric (TE) performance of conducting polymers. Many efforts have been devoted to the acquisition of a high TE performance for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by oxidation/reduction post treatment to achieve an effective compromise. However, a strong oxidant/reductant is usually employed to tune the TE performance of PEDOT:PSS with high electrical conductivity (σ) and Seebeck coefficient ( S), and it also presents a number of operational challenges depending on a fast reaction rate. Herein, nontoxic polyethylenimine ethoxylated (PEIE) served as a reductant to successfully realize an enhanced S for PEDOT:PSS, besides playing a significant anion-blocking role in enabling the efficient modulation of the oxidation level by sulfuric acid (H₂SO₄) with a longer operating time. Eventually, a good PEDOT-rich nanocrystal is achieved by a sequential dipping process in PEIE/ethylene glycol and H₂SO₄ solutions. The large TE power factor of 133 μW m^-1 K^-2 can be ascribed to the good formation of PEDOT-rich nanocrystals and an effective compromise between σ and S of PEDOT:PSS films. A mechanism was elucidated for the efficient regulation of σ and S enabling high performance of organic TE materials.

Investigating enhanced thermoelectric performance of graphene-based nano-structures

Recently, it has been demonstrated that graphene nano-ribbons (GNRs) exhibit superior thermoelectric performance compared to graphene sheets. However, the underlying mechanism behind this enhancement has not been systematically investigated and significant opportunity remains for further enhancement of the thermoelectric performance of GNRs by optimizing their charge carrier concentration. In this work, we modulate the carrier concentration of graphene-based nano-structures using a gate voltage and investigate the resulting carrier-concentration-dependent thermoelectric parameters using the Boltzmann transport equations. We investigate the effect of energy dependent scattering time and the role of substrate-induced charge carrier fluctuation in optimizing the Seebeck coefficient and power factor. Our approach predicts the scattering mechanism and the extent of the charge carrier fluctuation in different samples and explains the enhancement of thermoelectric performance of GNR samples. Subsequently, we propose a route towards the enhancement of thermoelectric performance of graphene-based devices which can also be applied to other two-dimensional materials.

Thermoelectric Transport in Nanocomposites

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed.

Energy Harvesters for Wearable and Stretchable Electronics: From Flexibility to Stretchability

The rapid advancements of wearable electronics have caused a paradigm shift in consumer electronics, and the emerging development of stretchable electronics opens a new spectrum of applications for electronic systems. Playing a critical role as the power sources for independent electronic systems, energy harvesters with high flexibility or stretchability have been the focus of research efforts over the past decade. A large number of the flexible energy harvesters developed can only operate at very low strain level (≈0.1%), and their limited flexibility impedes their application in wearable or stretchable electronics. Here, the development of highly flexible and stretchable (stretchability >15% strain) energy harvesters is reviewed with emphasis on strategies of materials synthesis, device fabrication, and integration schemes for enhanced flexibility and stretchability. Due to their particular potential applications in wearable and stretchable electronics, energy-harvesting devices based on piezoelectricity, triboelectricity, thermoelectricity, and dielectric elastomers have been largely developed and the progress is summarized. The challenges and opportunities of assembly and integration of energy harvesters into stretchable systems are also discussed.

Length-dependent thermal transport in one-dimensional self-assembly of planar π-conjugated molecules

This work reports a thermal transport study in quasi-one-dimensional organic nanostructures self-assembled from conjugated planar molecules via π-π interactions. Thermal resistances of single crystalline copper phthalocyanine (CuPc) and perylenetetracarboxylic diimide (PTCDI) nanoribbons are measured via a suspended thermal bridge method. We experimentally observed the deviation from the linear length dependence for the thermal resistance of single crystalline β-phase CuPc nanoribbons, indicating possible subdiffusion thermal transport. Interestingly, a gradual transition to the linear length dependence is observed with the increase of the lateral dimensions of CuPc nanoribbons. The measured thermal resistance of single crystalline CuPc nanoribbons shows an increasing trend with temperature. However, the trend of temperature dependence of thermal resistance is reversed after electron irradiation, i.e., decreasing with temperature, indicating that the single crystalline CuPc nanoribbons become 'amorphous'. Similar behavior is also observed for PTCDI nanoribbons after electron irradiation, proving that the electron beam can induce amorphization of single crystalline self-assembled nanostructures of planar π-conjugated molecules. The measured thermal resistance of the 'amorphous' CuPc nanoribbon demonstrates a roughly linear dependence on the nanoribbon length, suggesting that normal diffusion dominates thermal transport.

Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment

The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tellurium-PEDOT:PSS (Te-PEDOT:PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PEDOT:PSS and Te-PEDOT:PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm⁻¹, respectively was achieved by simple chemical treatment with H₂SO₄. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H₂SO₄ solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m⁻¹ K⁻², respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te-PEDOT:PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat.

Thermoelectric power of oriented thin-film organic conductors

The temperature dependence of thermoelectric power is investigated down to low temperatures for oriented thin films of organic conductors.

Organic thermoelectric materials: emerging green energy materials converting heat to electricity directly and efficiently

The abundance of solar thermal energy and the widespread demands for waste heat recovery make thermoelectric generators (TEGs) very attractive in harvesting low-cost energy resources. Meanwhile, thermoelectric refrigeration is promising for local cooling and niche applications. In this context there is currently a growing interest in developing organic thermoelectric materials which are flexible, cost-effective, eco-friendly and potentially energy-efficient. In particular, the past several years have witnessed remarkable progress in organic thermoelectric materials and devices. In this review, thermoelectric properties of conducting polymers and small molecules are summarized, with recent progresses in materials, measurements and devices highlighted. Prospects and suggestions for future research efforts are also presented. The organic thermoelectric materials are emerging candidates for green energy conversion.

Biomolecule-doped PEDOT with three-dimensional nanostructures as efficient catalyst for oxygen reduction reaction

Metal macro-cyclic compounds have drawn considerable attention as alternative catalysts for oxygen reduction reaction. However, the continuous pyrolysis process usually needed for improving the performance of these compounds require an elevated temperature and complicated procedures, thus leading to an unpredictable transformation of the chemical structures and limiting their applications. Herein, we develop a new insight to fabricating hemin-doped poly (3,4-ethylenedioxythiophene) (PEDOT) with controllable three-dimensional nanostructures via a one-step, tri-phase, self-assembled polymerization routine. We demonstrate that the hemin-induced synergistic effect results in a very high 4-electron oxygen reduction activity, a better stability, and free from methanol crossover effects even in a neutral phosphate buffer solution (PBS).

Facile preparation and thermoelectric properties of Bi₂Te₃ based alloy nanosheet/PEDOT:PSS composite films

Bi2Te3 based alloy nanosheet (NS)/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) composite films were prepared separately by spin coating and drop casting techniques. The drop cast composite film containing 4.10 wt % Bi2Te3 based alloy NSs showed electrical conductivity as high as 1295.21 S/cm, which is higher than that (753.8 S/cm) of a dimethyl sulfoxide doped PEDOT:PSS film prepared under the same condition and that (850-1250 S/cm) of the Bi2Te3 based alloy bulk material. The composite film also showed a very high power factor value, ∼32.26 μWm(-1) K(-2). With the content of Bi2Te3 based alloy NSs increasing from 0 to 4.10 wt %, the electrical conductivity and Seebeck coefficient of the composite films increase simultaneously.

Inkjet-printed flexible organic thin-film thermoelectric devices based on p- and n-type poly(metal 1,1,2,2-ethenetetrathiolate)s/polymer composites through ball-milling

In this article, we put forward a simple method for the synthesis of thermoelectric (TE) composite materials. Both n- and p-type composites were obtained by ball-milling the insoluble and infusible metal coordination polymers with other polymer solutions. The particle size, film morphology and composition were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The TE properties of the drop-cast composite film were measured at different temperatures. An inkjet-printed flexible device was fabricated and the output voltage and short-circuit current at various hot-side temperatures (Thot) and temperature gradients (ΔT) were tested. The composite material not only highly maintained the TE properties of the pristine material but also greatly improved its processability. This method can be extended to other insoluble and infusible TE materials for solution-processed flexible TE devices.

Intrinsically conducting polymer nanowires for biosensing

The fabrication of conductive polymer nanowires and their sensing of nucleic acids, proteins and pathogens is reviewed in this feature article.

Facile fabrication of PEDOT:PSS/polythiophenes bilayered nanofilms on pure organic electrodes and their thermoelectric performance

A pure organic PEDOT:PSS nanofilm was used as a working electrode for the first time to electrodeposit polymer films of polythiophene (PTh) and its derivatives in a boron trifluoride diethyl ether (BFEE) solution, fabricating a novel generation of bilayered nanofilms. Cyclic voltammetry (CV) demonstrated good electrochemical stability of the as-formed films. Structures and surface morphologies were systematically investigated by the characterizations of cross-section SEM, FT-IR, UV-vis, SEM, and AFM. The resulting films revealed stable and enhanced thermoelectric (TE) performances. The electrical conductivity values of PEDOT:PSS/PTh, PEDOT:PSS/P3MeT, and PEDOT:PSS/P3HT nanofilms were determined to be 123.9, 136.5, and 200.5 S cm(-1), respectively. The power factor reached up to be a maximum value of 5.79 μW m(-1) k(-2). Thus, this technique offers a facile approach to a class of bilayered nanofilms, and it may provide a general strategy for fabricating a new generation of conducting polymers for more practical applications.

A review on the fabrication of polymer-based thermoelectric materials and fabrication methods

Thermoelectricity, by converting heat energy directly into useable electricity, offers a promising technology to convert heat from solar energy and to recover waste heat from industrial sectors and automobile exhausts. In recent years, most of the efforts have been done on improving the thermoelectric efficiency using different approaches, that is, nanostructuring, doping, molecular rattling, and nanocomposite formation. The applications of thermoelectric polymers at low temperatures, especially conducting polymers, have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. In this review, we will focus on exploring new types of polymers and the effects of different structures, concentrations, and molecular weight on thermoelectric properties. Various strategies to improve the performance of thermoelectric materials will be discussed. In addition, a discussion on the fabrication of thermoelectric devices, especially suited to polymers, will also be given. Finally, we provide the challenge and the future of thermoelectric polymers, especially thermoelectric hybrid model.

NIR-sensitive poly(3,4-ethylenedioxyselenophene) derivatives for transparent photo-thermo-electric converters

Electrochromism, photothermal effect, and thermoelectric properties of hexyl-derivatized poly(3,4-ethylenedioxyselenophene) are investigated by precisely controlling the morphology. These properties are clearly demonstrated by controlling the applied electrical potential of the polymer films. Especially, the doped polymer film at -0.1 V reveals the highest photothermal conversion efficiency and a power factor of 42.5% and 354.7 μW m(-1) K(-2) , respectively. Efficient visible to near-infrared absorption, photon to heat, and heat to electric conversion has been realized in one film that could benefit in exploiting multifunctional film displays, invisible NIR sensors, photodynamic theragnosis, and thermoelectric devices.

Nickel nanoparticle chains inside carbonized polymer nanofibers: preparation by electrospinning and ion-beam irradiation

Novel organic-inorganic composite 1D nanostructures composed of carbonized conductive nanofibers and nickel nanoparticle chains were prepared by the combination of an electrospinning method from metal complex-containing polymer solutions and an ion-beam irradiation technique. The nickel nanoparticle chains were formed by self-assembly inside the carbonized nanofibers, which were characterized by STEM-HAADF observation and XPS spectroscopy. The existence of nickel complexes and the subsequent formation of nickel nanoparticles enhanced the electrical conductivities of carbonized nanofibers to reach above 0.5 S cm(-1) for the 6FDA-6FAP nanofibrous membrane containing 5.0 wt% Ni(acac)2 after ion-beam irradiation at an ion fluence of 1 × 10(16) ions per cm(2).

Effect of interfacial properties on polymer-nanocrystal thermoelectric transport

The electrical behavior of a conducting-polymer/inorganic-nanowire composite is explained with a model in which carrier transport occurs predominantly through a highly conductive volume of polymer that exists at the polymer-nanowire interface. This result highlights the importance of controlling nanoscale interfaces for thermoelectric materials, and provides a general route for improving carrier transport in organic/inorganic composites.

Metal nanoparticles for energy conversion

Energy has emerged as a strategic priority not only in research but also in all aspects of human lives. Most worldwide problems could be solved if energy were plentiful. In order to solve the energy problem, the following methods could be applicable: the creation of electricity from renewable energy resources, increase in conversion efficiency from fossil fuels to electricity, recovery of electricity from exhaust heat energy, and reduction of energy consumption. Nanotechnologies have already shown good promise in addressing and offering solutions in these priority areas. Here, we have demonstrated the application of metal nanoparticles (NPs) to electrocatalysts for the polyelectrolyte fuel cell (increase in conversion efficiency) and to additives to form hybrids with organic thermoelectric materials of conducting polymers (recovery of energy from exhaust heat). Thus, Pt monometallic and AuPt bimetallic NPs were used for electrocatalysts with high performance, and Pt and Au NPs were applied to hybrid thermoelectric materials to fabricate hybrid films with increasing thermoelectric performance for conversion of the exhaust heat near room temperature.

Virus-poly(3,4-ethylenedioxythiophene) biocomposite films

Virus-poly(3,4-ethylenedioxythiophene) (virus-PEDOT) biocomposite films are prepared by electropolymerizing 3,4-ethylenedioxythiophene (EDOT) in aqueous electrolytes containing 12 mM LiClO(4) and the bacteriophage M13. The concentration of virus in these solutions, [virus](soln), is varied from 3 to 15 nM. A quartz crystal microbalance is used to directly measure the total mass of the biocomposite film during its electrodeposition. In combination with a measurement of the electrodeposition charge, the mass of the virus incorporated into the film is calculated. These data show that the concentration of the M13 within the electropolymerized film, [virus](film), increases linearly with [virus](soln). The incorporation of virus particles into the PEDOT film from solution is efficient, resulting in a concentration ratio of [virus](film):[virus](soln) ≈ 450. Virus incorporation into the PEDOT causes roughening of the film topography that is observed using scanning electron microscopy and atomic force microscopy (AFM). The electrical conductivity of the virus-PEDOT film, measured perpendicular to the plane of the film using conductive tip AFM, decreases linearly with virus loading, from 270 μS/cm for pure PEDOT films to 50 μS/cm for films containing 100 μM virus. The presence on the virus surface of displayed affinity peptides did not significantly influence the efficiency of incorporation into virus-PEDOT biocomposite films.

A chemically-responsive nanojunction within a silver nanowire

The formation of a nanometer-scale chemically responsive junction (CRJ) within a silver nanowire is described. A silver nanowire was first prepared on glass using the lithographically patterned nanowire electrodeposition method. A 1-5 nm gap was formed in this wire by electromigration. Finally, this gap was reconnected by applying a voltage ramp to the nanowire resulting in the formation of a resistive, ohmic CRJ. Exposure of this CRJ-containing nanowire to ammonia (NH(3)) induced a rapid (<30 s) and reversible resistance change that was as large as ΔR/R(0) = (+)138% in 7% NH(3) and observable down to 500 ppm NH(3). Exposure to water vapor produced a weaker resistance increase of ΔR/R(0,H(2)O) = (+)10-15% (for 2.3% water) while nitrogen dioxide (NO(2)) exposure induced a stronger concentration-normalized resistance decrease of ΔR/R(0,NO(2)) = (-)10-15% (for 500 ppm NO(2)). The proposed mechanism of the resistance response for a CRJ, supported by temperature-dependent measurements of the conductivity for CRJs and density functional theory calculations, is that semiconducting p-type Ag(x)O is formed within the CRJ and the binding of molecules to this Ag(x)O modulates its electrical resistance.

Virus-polymer hybrid nanowires tailored to detect prostate-specific membrane antigen

We demonstrate the de novo fabrication of a biosensor, based upon virus-containing poly(3,4-ethylene-dioxythiophene) (PEDOT) nanowires, that detects prostate-specific membrane antigen (PSMA). This development process occurs in three phases: (1) isolation of a M13 virus with a displayed polypeptide receptor, from a library of ≈10(11) phage-displayed peptides, which binds PSMA with high affinity and selectivity, (2) microfabrication of PEDOT nanowires that entrain these virus particles using the lithographically patterned nanowire electrodeposition (LPNE) method, and (3) electrical detection of the PSMA in high ionic strength (150 mM salt) media, including synthetic urine, using an array of virus-PEDOT nanowires with the electrical resistance of these nanowires for transduction. The electrical resistance of an array of these nanowires increases linearly with the PSMA concentration from 20 to 120 nM in high ionic strength phosphate-buffered fluoride (PBF) buffer, yielding a limit of detection (LOD) for PSMA of 56 nM.