Highly sensitive ethylene glycol-doped PEDOT-PSS organic thin films for LPG sensing

Thermoelectric Performance of Hybrid Inorganic/Organic Composites Based on PEDOT:PSS/Tin(II) Oxide

PEDOT

PSS(poly(3,4-ethylenedioxylthiophene):poly(styrenesulfonate))-based composites often exhibit remarkable characteristics regarding high electrical conductivity and great processability, being a suitable candidate for thermoelectric (TE) applications. To increase its performance, PEDOT:PSS is commonly blended with scarce and toxic inorganic compounds based on Se, Te or Bi. In this work we propose the use of one p-type metal oxide semiconductor (MOs): tin(II) oxide (SnO), motivated by its abundance and low toxicity. Hybrid PEDOT:PSS/SnO composites were obtained by firstly blending Ethylene glycol (EG) with PEDOT:PSS and then by adding p-type SnO, previously synthesized by a chemical route. The mixture was deposited via spin-coating onto glass substrates. The Power Factor (PF) of the composites increased by a factor of 300 with the combined EG/SnO composition.

Extracellular vesicles-based point-of-care testing for the diagnosis and monitoring of Alzheimer's disease

Alzheimer's disease (AD) is a debilitating condition that affects millions of people worldwide. One promising strategy for detecting and monitoring AD early on is using extracellular vesicles (EVs)-based point-of-care testing; however, diagnosing AD using EVs poses a challenge due to the low abundance of EV-biomarkers. Here, we present a fully integrated organic electrochemical transistor (OECT) that enables high accuracy, speed, and convenience in the detection of EVs from AD patients. We incorporated self-aligned acoustoelectric enhancement of EVs on a chip that rapidly propels, enriches, and specifically binds EVs to the OECT detection area. With our enhancement of pre-concentration, we increased the sensitivity to a limit of detection of 500 EV particles/μL and reduced the required detection time to just two minutes. We also tested the sensor on an AD mouse model to monitor AD progression, examined mouse Aβ EVs at different time courses, and compared them with intraneuronal Aβ cumulation using MRI. This innovative technology has the potential to diagnose Alzheimer's and other neurodegenerative diseases accurately and quickly, enabling monitoring of disease progression and treatment response.

A holistic review on the recent trends, advances, and challenges for high-precision room temperature liquefied petroleum gas sensors

Liquefied petroleum gas (LPG), which is mainly composed of hydrocarbons, such as propane and butane, is a flammable gas that is considered a clean source of energy. Currently, the overwhelming use of LPG as fuel in vehicles, domestic settings, and industry has led to several incidents and deaths globally due to leakage. As a result, the appropriate detection of LPG is vital; thus, gas-sensing devices that can monitor this gas rapidly and accurately at room temperature, are required. This work reviews the current advances in LPG gas sensors, which operate at room temperature. The influences of the synthesis methods and parameters, doping, and use of catalysts on the sensing performance are discussed. The formation of heterostructures made from semiconducting metal oxides, polymers, and graphene-based materials, which enhance the sensor selectivity and sensitivity, is also discussed. The future trends and challenges confronted in the advancement of LPG room temperature operational gas sensors, and critical ideas concerning the future evolution of LPG gas sensors, are deliberated. Additionally, the advancements in the next-generation gas sensors, such as the wireless detection of LPG leakage, self-powered sensors driven by triboelectric/piezoelectric mechanisms, and artificial intelligent systems are also reviewed. This review further focuses on the use of smartphones to circumvent the use of costly instruments and paves the way for cost-efficient and portable monitoring of LPG. Finally, the approach of utilizing the Internet of Things (IoT) to detect/monitor the leakage of LPG has also been discussed, which will provide better alerts to the users and thus minimize the effects of leakages.

Revealing the improved sensitivity of PEDOT:PSS/PVA thin films through secondary doping and their strain sensors application

The field of strain sensing involves the ability to measure an electrical response that corresponds to a strain. The integration of synthetic and conducting polymers can create a flexible strain sensor with a wide range of applications, including soft robotics, sport performance monitoring, gaming and virtual reality, and healthcare and biomedical engineering. However, the use of insulating synthetic polymers can impede the semiconducting properties of sensors, which may reduce sensor sensitivity. Previous research has shown that the doping process can significantly enhance the electrical performance and ionic conduction of conducting polymers, thereby strengthening their potential for use in electronic devices. However the full effects of secondary doping on the crystallinity, stretchability, conductivity, and sensitivity of conducting polymer blends have not been studied. In this study, we investigated the effects of secondary doping on the properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/poly(vinyl alcohol) (PEDOT:PSS/PVA) polymer blend thin films and their potential use as strain sensors. The thin films were prepared using a facile drop-casting method. Morphology analysis using profilometry and atomic force microscopy confirmed the occurrence of phase segregation and revealed surface roughness values. This evidence provided a comprehensive understanding of the chemical interactions and physical properties of the thin films, and the effects of doping on these properties. The best films were selected and applied as sensitive strain sensors. EG-PEDOT:PSS/PVA thin films showing a significant increase of conductivity values from the addition of 1 vol% to 12 vol% addition, with conductivity values of 8.51 × 10-5 to 9.42 × 10-3 S cm-1. Our 12% EG-PEDOT:PSS/PVA sensors had the highest GF value of 2000 too. We compared our results with previous studies on polymeric sensors, and it was found that our sensors quantitatively had better GF values. Illustration that demonstrates the DMSO and EG dopant effects on PEDOT:PSS structure through bonding interaction, crystallinity, thermal stability, surface roughness, conductivity and stretchability was also provided. This study suggests a new aspect of doping interaction that can enhance the conductivity and sensitivity of PEDOT:PSS for device applications.

High Performance of Carbon Monoxide Gas Sensor Based on a Novel PEDOT:PSS/PPA Nanocomposite

In this work, the carbon monoxide (CO) detection property of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/poly(p-anisidine) (PEDOT:PSS/PPA) nanocomposite was systematically investigated at room temperature. The PEDOT:PSS/PPA nanocomposite was synthesized by the cost-effective "in situ chemical oxidation polymerization" technique. The electric, optical, spectroscopic, and structural properties of the as-prepared nanomaterials were analyzed with I-V, UV-vis, Raman, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) spectroscopies. Topological investigations of materials were conducted by atomic force microscopy (AFM). The gas-sensing performance of the PEDOT:PSS/PPA and PEDOT:PSS nanocomposites toward CO gas in the concentration range of 50-300 ppm at room temperature was explored, and their performances were compared. The PEDOT:PSS/PPA sensor shows a perfectly linear response to different concentrations (50-300 ppm) of CO gas (R ² = 0.9885), and the response time and recovery time of the CO gas sensor (100 ppm) can be about 58 and 61 s, respectively, showing high sensitivity to CO gas and rapid response recovery with outstanding stability. Thus, the PEDOT:PSS/PPA-based sensors, with their impressive sensing performance, may give assurance for future high-performance CO-sensing applications.

Additive Effect on the Structure of PEDOT:PSS Dispersions and Its Correlation with the Structure and Morphology of Thin Films

We reported on the interaction between poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and high-boiling-point additives in PEDOT:PSS aqueous dispersions and in the final polymer films with the aim of stablishing correlations between the structure of both inks and solid thin films. By Small-Angle X-ray Scattering (SAXS) using synchrotron radiation, it was found that the structural changes of dispersions of PEDOT:PSS with high-boiling-point additives can be explained as a two-step mechanism depending on the additive concentration. A compaction of PEDOT:PSS grains was observed at low concentrations while a swelling of the grains together with a phase segregation between PEDOT and PSS segments was evidenced at larger concentrations. Thin films' morphology and structure were investigated by atomic force microscopy (AFM) and synchrotron Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) respectively. Our two-step model provides an explanation for the small and sharp domains of PEDOT:PSS thin films observed for low-additive concentrations (first step) and larger domains and roughness found for higher-additive concentrations (second step). A reduction of the ratio of PSS in PEDOT:PSS thin films upon the presence of additives was also observed. This can be related to a thinning of the PSS shells of PEDOT:PSS grains in the dispersion. The results discussed in this work provide the basis for a controlled tuning of PEDOT:PSS thin films structure and the subsequent electrical properties.

Deposition and Characterization of Innovative Bulk Heterojunction Films Based on CuBi2O4 Nanoparticles and Poly(3,4 ethylene dioxythiophene):Poly(4-styrene sulfonate) Matrix

This work presents the deposition and study of the semiconductor behavior of CuBi2O4 nanoparticles (NPs) with an average crystallite size of 24 ± 2 nm embedded in poly(3,4 ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) films. The CuBi2O4 NP bandgap was estimated at 1.7 eV, while for the composite film, it was estimated at 2.1 eV, due to PEDOT:PSS and the heterojunction between the polymer and the NPs. The charge transport of the glass/ITO/PEDOT:PSS-CuBi2O4 NP/Ag system was studied under light and dark conditions by means of current–voltage (I–V) characteristic curves. In natural-light conditions, the CuBi2O4 NPs presented electric behavior characterized by three different mechanisms: at low voltages, the behavior follows Ohm’s law; when the voltage increases, charge transport occurs by diffusion between the NP–polymer interfaces; and at higher voltages, it occurs due to the current being dominated by the saturation region. Due to their crystalline structure, their low bandgap in films and the feasibility of integrating them as components in composite films with PEDOT:PSS, CuBi2O4 NPs can be used as parts in optoelectronic devices.

Design and development of highly sensitive PEDOT-PSS/AuNP hybrid nanocomposite-based sensor towards room temperature detection of greenhouse methane gas at ppb level

Herein, we present fabrication of a novel methane sensor based on poly (3,4-ethylenedioxythiophene:poly (styrene sulfonic acid)) (p-PEDOT-PSS) and gold nanoparticles (AuNPs) treated with dimethyl sulfoxide (DMSO) and Zonyl using a spin coating technique. The nanocomposite films were further post treated with H2SO4 to improve the charge transport mechanism. The structural and morphological features of the composites were analyzed through scanning electronic microscopy, transmission electron microscopy, Fourier transform infra-red spectroscopy, UV-Vis spectroscopy and thermogravimetric analysis. Treatment with organic solvents and post treatment of H2SO4 significantly enhances the conductivity of the composite to 1800 S cm-1. The fabricated sensor shows an excellent sensing response, fast response and recovery time along with acceptable selectivity towards methane gas at ppb concentrations. Due to a simple fabrication technique, excellent conductivity, superior sensing performance and improved mechanical properties, the sensor fabricated in this study could potentially be used to detect greenhouse methane gas at low concentrations.

Nanostructured cobalt antimonate: a fast responsive and highly stable sensing material for liquefied petroleum gas detection at room temperature

Herein, cobalt antimonate (CoSb2O6) nanospheres were fabricated via the sol-gel spin-coating process and employed as a functional liquefied petroleum gas (LPG) sensor at room temperature (25 °C). The microstructure of the fabricated CoSb2O6 thin films (thickness ∼ 250 nm) was analyzed via scanning electron microscopy, which revealed the growth of nanospheres having an average diameter of ∼45 nm. The XRD analysis demonstrated the crystalline nature of CoSb2O6 with a crystallite size of ∼27 nm. Finally, the fabricated thin films were investigated as sensors for LPG and carbon dioxide (CO2) at room temperature (25 °C) and 55% R.H. (relative humidity) with different concentrations in the range of 1000-5000 ppm. The sensing results demonstrated greater variations in the electrical properties of films for the incoming LPG than that of the CO2 gas adsorption. Furthermore, to ensure the long-term stability of fabricated sensors, they were tested periodically at 10 days interval, spanning a total duration of 60 days. In summary, our fabricated LPG sensor displayed high sensitivity (1.96), repeatability, quick response time (21 s) and high long-term stability (99%). Therefore, CoSb2O6 nanospheres can be functionalized as a potential LPG-sensitive material characterized by high sensitivity, reliability and stability at room temperature.

Radio-Frequency/Microwave Gas Sensors Using Conducting Polymer

In this review, the advances in radio-frequency (RF) /microwave chemical gas sensors using conducting polymers are discussed. First, the introduction of various conducting polymers is described. Only polyaniline (PANi), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), which are mainly used for gas sensors in RF/microwave region, are focused in this review. Sensing mechanism of the three conducting polymers are presented. And the RF/microwave characteristics and RF/microwave applications of the three conducting polymers are discussed. Moreover, the gas sensors using conducting polymers in RF/microwave frequencies are described. Finally, the the challenges and the prospects of the next generation of the RF/microwave based chemical sensors for wireless applications are proposed.

Virus Bioresistor (VBR) for Detection of Bladder Cancer Marker DJ-1 in Urine at 10 pM in One Minute

DJ-1, a 20.7 kDa protein, is overexpressed in people who have bladder cancer (BC). Its elevated concentration in urine allows it to serve as a marker for BC. However, no biosensor for the detection of DJ-1 has been demonstrated. Here, we describe a virus bioresistor (VBR) capable of detecting DJ-1 in urine at a concentration of 10 pM in 1 min. The VBR consists of a pair of millimeter-scale gold electrodes that measure the electrical impedance of an ultrathin (≈ 150-200 nm), two-layer polymeric channel. The top layer of this channel (90-105 nm in thickness) consists of an electrodeposited virus-PEDOT (PEDOT is poly(3,4-ethylenedioxythiophene)) composite containing embedded M13 virus particles that are engineered to recognize and bind to the target protein of interest, DJ-1. The bottom layer consists of spin-coated PEDOT-PSS (poly(styrenesulfonate)). Together, these two layers constitute a current divider. We demonstrate here that reducing the thickness of the bottom PEDOT-PSS layer increases its resistance and concentrates the resistance drop of the channel in the top virus-PEDOT layer, thereby increasing the sensitivity of the VBR and enabling the detection of DJ-1. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise (S/N > 100) and excellent sensor-to-sensor reproducibility characterized by coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a concentration of 30 pM, near the 10 pM limit of detection (LOD), encompassing four orders of magnitude in concentration.

Hydroxymethyl-Functionalized PEDOT-MeOH:PSS for Perovskite Solar Cells

Poly(hydroxymethylated-3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT-MeOH:PSS) conducting polymers are synthesized and incorporated in inverted structured perovskite solar cells (PVSCs) as hole transport materials. The highest occupied molecular orbital of PEDOT-MeOH is lowered by adding a hydroxymethyl (-MeOH) functional group to ethylenedioxythiophene (EDOT), and thus, the work function of PEDOT-MeOH:PSS is increased. Additionally, hydrogen bonding can be formed among EDOT-MeOH monomers and between EDOT-MeOH monomers and sulfate groups on PSS, which promotes PEDOT-MeOH chain growth and enhances PSS doping. The electronic, microstructural, and surface morphological properties of PEDOT-MeOH:PSS are modified by changing the amounts of PSS and the ferric oxidizing agent used in the polymerization and by adding ethylene glycol in the postsynthesis treatment. The PVSCs based on ethylene-glycol-treated PEDOT-MeOH:PSS overperform the PVSCs based on commercial PEDOT:PSS because of the better energetic alignment and the enhancement of PEDOT-MeOH:PSS electrical conductivity. This work opens the way to develop new hole transport materials for highly efficient inverted PVSCs.

High performance flexible supercapacitors based on secondary doped PEDOT-PSS-graphene nanocomposite films for large area solid state devices

In this work, we propose the development of high performance and flexible supercapacitors using reduced graphene oxide (rGO) incorporated poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT-PSS) nanocomposites by secondary doping. The structural and morphological features of the composite film were analyzed in detail using SEM, AFM, FTIR, XPS and TGA. Secondary doping of ethylene glycol (EG) assisted by rGO incorporation significantly enhances the room temperature conductivity of PEDOT-PSS films from 3 S cm-1 to nearly 1225 S cm-1 for a 10 wt% composite. The secondary doped PEDOT-PSS:EG/rGO composite film demonstrated improved electrochemical performances with specific capacitance of 174 (F g-1) and energy density of 810 (W h kg-1) which is nearly 4 times greater than pristine PEDOT-PSS due to synergetic interactions between rGO and PEDOT-PSS. The prepared composite films show long term stability with capacitance retention of over 90% after 5000 cycles of charging-discharging. The nanocomposite films used in the present investigation demonstrates percolative behavior with a percolation threshold at 10 wt% of rGO in PEDOT-PSS. The assembled supercapacitor device could be bent and rolled-up without a decrease in electrochemical performance indicating the potential to be used in practical applications. To demonstrate the practical applicability, a rolled-up supercapacitor device was constructed that demonstrates operation of a red LED for 40 seconds when fully charged. This study will provide new dimensions towards designing cost effective, flexible and all solid-state supercapacitors with improved electrochemical performance using electrodes based on secondary doped PEDOT-PSS/rGO organic thin films.

Fabrication and Characterization of Humidity Sensors Based on Graphene Oxide-PEDOT:PSS Composites on a Flexible Substrate

In this paper, we present a simple, fast, and cost-effective method for the large-scale fabrication of high-sensitivity humidity sensors on flexible substrates. These sensors consist of a micro screen-printed capacitive structure upon which a sensitive layer is deposited. We studied two different structures and three different sensing materials by modifying the concentration of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) in a graphene oxide (GO) solution. The results show that the aggregation of the PEDOT:PSS to the GO can modify its electrical properties, boosting the performance of the capacitive sensors in terms of both resistive losses and sensitivity to relative humidity (RH) changes. Thus, in an area less than 30 mm2, the GO/PEDOT:PSS-based sensors can achieve a sensitivity much higher (1.22 nF/%RH at 1 kHz) than other similar sensors presented in the literature which, together with their good thermal stability, time response, and performance over bending, demonstrates that the manufacturing approach described in this work paves the way for the mass production of flexible humidity sensors in an inexpensive way.