Dowex Research Articles

PEDOT:PSS deposition in OECTs: Inkjet printing, aerosol jet printing and spin coating

As the world moves towards integrating new functionalities into everyday objects, the demand for diverse substrates grows, making additive manufacturing an invaluable tool. Organic electronic materials have played a major role in this transition thanks to their excellent electronic and mechanical properties, adaptability and solution processability.The aim of this study is to compare spin coating, inkjet printing (IJP), and aerosol jet printing (AJP) for applying poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the channel material in organic electrochemical transistors (OECTs). This work investigates the often-overlooked impact of deposition techniques on the electrical performance of OECTs. Spin coating has been analysed as a reference technique, while AJP and IJP are addressed as promising pathways towards fully printed OECTs.The normalized transconductance and Ion/Ioff ratio have been analysed as figures of merit for this study. AJP devices have shown the best performance, displaying a normalized transconductance of 885 S∙nm and an Ion/Ioff ratio around 103. The spin coated OECTs showed a slightly lower normalized transconductance (740 S∙nm) and much lower Ion/Ioff ratio in the order of 101. Last, IJP exhibited a transconductance of 433 S∙nm and a Ion/Ioff ratio in the order of 102.This work could be beneficial for a wide range of applications, adding an additional degree of freedom to the tunability of the OECT channel properties. It also opens the discussion for more comprehensive studies on the films from a materials perspective.

Effects of transparent conducting electrodes and hole transport layers on the performance of MAPbI3 solar cells fabricated on PET substrates

This study investigates how the performance of perovskite solar cells (PSCs) made on polyethylene terephthalate (PET) substrates depends on transparent conducting electrodes (TCEs) and hole transport layers (HTLs). We fabricated PSCs using commercially available PET/TCEs and compared their performance with PSCs manufactured on Glass/indium tin oxide (ITO) substrates. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with varying levels of acidity and NiO nanoparticles were used as HTLs. The current density-voltage characteristics of PSCs made on PET/TCEs were found to be significantly lower when highly acidic PEDOT:PSS was used as the HTL. However, this was not observed for PSCs made on Glass/ITO. To investigate the interaction between HTL and TCE, atomic force microscopy was carried out after dipping the TCEs in PEDOT:PSS solutions of different acidity. X-ray photoelectron spectroscopy measurements further revealed differences in the chemical composition between ITO film on PET vs. on glass. Our results indicate that the performance of PSCs depends both on the TCE substrates and HTLs, which can be explained by their chemical interaction.

Polystyrene Sulfonate Resin as an Ophthalmic Carrier for Enhanced Bioavailability of Ligustrazine Phosphate Controlled Release System

Topical ocular sustained-release drug delivery systems represent an effective strategy for the treatment of ocular diseases, for which a suitable carrier has yet to be sufficiently developed. Herein, an eye-compatible sodium polystyrene sulfonate resin (SPSR) was synthesized with a uniform particle size of about 3 μm. Ligustrazine phosphate (LP) was adsorbed to SPSR by cation exchange to form LP@SPSR. LP@SPSR suspension eye drops were further developed using the combination of Carbopol 934P and xanthan gum as suspending agents. The LP@SPSR suspension showed a sustained release in vitro, which was consistent with the observed porcine corneal penetration ex vivo. Pharmacokinetics in tear fluid of rabits indicated that LP@SPSR suspension led to prolonged ocular retention of LP and a 2-fold improved the area under the drug concentration-time curve (AUC0-t). Pharmacokinetics in the aqueous humor of rabbits showed 2.8-fold enhancement in the AUC0-t compared to LP solution. The LP@SPSR suspension exhibited no cytotoxicity to human corneal epithelial cells, nor irritation was observed in rabbit eyes. Thus, the LP@SPSR suspension has been validated as a safe and sustained release system leading to enhanced ophthalmic bioavailability for treating ocular diseases.

All-glycerogel stretchable supercapacitor with stable performance in a wide temperature window from −20 to 80 °C

Stretchable supercapacitors (s-SCs) are extensively used in portable and wearable smart electronic devices. However, existing s-SCs exhibit low electrical conductivity/stretchability, weak electrode/electrolyte interfaces, and limited operational temperatures, which severely limit their practical applications. Accordingly, we have developed a stretchable glycerogel supercapacitor (s-GGSC) addressing these limitations. Electrode is fabricated by glycerol-mediated robust integration of poly(vinyl alcohol) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate through a simple strategy of partial drying–reswelling and thermal annealing. This eliminates the conventional trade-off between electrical conductivity and stretchability and provides adaptability to wide temperature ranges (−20 to 80 °C). A compatible electrolyte is also fabricated using poly(vinyl alcohol), lithium perchlorate, and glycerol. Heat-mediated facile exchange of inter- and intramolecular hydrogen bonding enables robust bonding between the electrode and electrolyte in the developed s-GGSC, thus solving interfacial problems under harsh mechanical conditions. The high electrical conductivity (1089 ± 49 S m−1) and fracture strain (232%) of the electrode preclude the use of an additional current collector. s-GGSC exhibits areal capacitance retentions of 90.92% and 93.27% after 7 d of incubation at −20 and 80 °C, respectively, and excellent cycling stability (81.48% capacitance retention) after 10,000 cycles. Furthermore, the areal capacitance of the device remains constant after intense mechanical deformations, such as bending, twisting, and stretching. s-GGSC outperforms existing flexible and/or stretchable supercapacitors under harsh conditions, confirming its suitability as a potential power source for wearable and stretchable smart electronic devices.

Harnessing the Benefits of PEDOT : PSS Conductive Coating for Prolonged Cycle Life of Copper Hexacyanoferrate in Aqueous Zinc‐Ion Batteries

AbstractThe utilization of copper hexacyanoferrate (CuHCF) as positive electrode material in aqueous zinc‐ion batteries (ZIBs) has gained significant attention due to its efficient (de−)intercalation of Zn2+ ions, cost‐effective synthesis, low toxicity, and high working potential. One approach to improve its electrochemical performance is to coat the CuHCF particles with conductive polymers, such as poly(3,4‐ethylenedioxythiophene): polystyrene sulfonate (PEDOT : PSS). In this study, we investigated the impact of the PEDOT : PSS as a coating on the electrochemical behavior and the cycle life of CuHCF for aqueous ZIB applications. Galvanostatic cycling performed at a current rate of 1 C relevant for the stationary application of the CuHCF/PEDOT : PSS electrodes having high mass loadings (10 mg cm−2 of active material) revealed significantly longer cycle life while maintaining a high Coulombic efficiency (≥ 99.5 %). The longest cycle life was achieved with CuHCF coated using a 4.5 wt. % PEDOT : PSS aqueous coating dispersion. These findings demonstrate the potential of conductive polymer coatings as a practical approach to enhance the electrochemical performance of positive electrode materials in aqueous Zinc‐ion batteries.

The performance of triethanolamine (TEOA)-doped Poly(3,4-ethylenedioxythiophene): Polystyrene sulfonate on MAPbI3-based solar cells

For over a decade, perovskite-based solar cells have attracted a good deal of attention due to their unique characteristics. Charge transport materials (CTMs) have a vital function in the performance of perovskite solar cells properly. Therefore, it is crucial to choose a suitable and affordable CTM. A commonly regarded conductive polymer combination called poly (3,4 ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) is mainly employed in organic and perovskite solar cells (PSCs) as a hole transport layer (HTL). Although PEDOT:PSS has benefits including affordability, simplicity, low-temperature processing, and ease of production, its acidic nature and low electrical conductivity pose drawbacks. In this research, it has been demonstrated that adding triethanolamine (TEOA) to the PEDOT:PSS solution improves the photovoltaic (PV) performance of sol-gel-based PSCs. The combination of enhanced conductivity and hole mobility of PEDOT:PSS layer with reduced perovskite trap density resulted in a more than 32 % boost in efficiency and better stability due to the basic characteristics of triethanolamine as well.

Charge-patterned nanofiltration membranes with polystyrene sulfonate particles and polyethyleneimine in cross-linked polyvinyl alcohol

Removing salinity has always been a challenge for wastewater treatment. Utilizing nanofiltration (NF) membranes is a promising approach. However, currently available NF membranes are less effective in monovalent salt removal. In this study, work toward the initial aim of fabricating charge mosaic membranes led to charge-patterned NF-selective films on polyether sulfone (PES) or polyacrylonitrile (PAN) support membranes, with similar rejection for mono- and divalent salts. The membranes were fabricated by a two-step layer assembly of first negatively charged polystyrene sulfonate (PSS) particles immobilized in a polyvinyl alcohol (PVA) layer, followed by coating a positively charged polyethyleneimine (PEI) layer. Both PVA and PEI were crosslinked using glutaraldehyde that had initially been impregnated into the support membrane. The type of support membrane, nanoparticle, PVA, and PEI concentrations during fabrication, as well as feed pH and salt concentration, play significant roles in separation performance of obtained composite membranes. Charge-patterned NF membranes fabricated using 0.5 wt.% PVA and 0.05 wt.% PSS for assembly of the first layer followed by coating 0.5 wt.% PEI solution had even somewhat higher rejection for monovalent salt (NaCl; ∼82%) compared to multivalent salts (Na2SO4, MgSO4, and MgCl2; ∼74%), at a permeance of 5.5 LMH/bar on the PES and 3.1 LMH/bar on the PAN support membrane.

Well-defined triphenylamine-containing polymers as hole-transporting layers in solution-processable organic light-emitting diodes via living anionic polymerization

In this study, we conducted anionic polymerization of N-[1,1′-biphenyl]-4-yl-N-(4′-ethenyl[1,1′-biphenyl]-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (A) incorporating a triphenylamine group as a hole-transporting unit using sec-butyllithium and potassium naphthalenide as initiators in tetrahydrofuran at −30 ℃ for 10 min. The resultant poly(A)s exhibited controlled molecular weights (Mn = 20.9−126.3 kg/mol) and narrow molecular weight distributions (Mw/Mn ≤ 1.12). The living nature of the propagating chain end of poly(A) was confirmed by postpolymerization. Additionally, block copolymerization of A with styrene (St) and 2-vinylpyridine (2VP) was performed to assess its relative reactivity. Copolymerization resulted in the precise synthesis of well-defined block copolymers with poly(A) segments. Thermal properties of poly(A) were investigated using thermogravimetric analysis and differential scanning calorimetry. Notably, the thermal annealing of poly(A) film at 230 ℃ for 10 min made it insoluble in toluene, indicating its solvent resistance. Thus, poly(A) was used as the hole-transporting layer (HTL) in solution-processable organic light-emitting diodes (OLEDs). A comparative analysis against a reference device containing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) revealed an enhancement in the performance of the OLED comprising thermally annealed poly(A) as the HTL. These results strongly suggest that poly(A) is a promising HTL material for solution-processable OLEDs.

Imidazolium-Based Sulfonating Agent to Control the Degree of Sulfonation of Aromatic Polymers and Enable Plastics-to-Electronics Upgrading.

The accumulation of plastic waste in the environment is a growing environmental, economic, and societal challenge. Plastic upgrading, the conversion of low-value polymers to high-value materials, could address this challenge. Among upgrading strategies, the sulfonation of aromatic polymers is a powerful approach to access high-value materials for a range of applications, such as ion-exchange resins and membranes, electronic materials, and pharmaceuticals. While many sulfonation methods have been reported, achieving high degrees of sulfonation while minimizing side reactions that lead to defects in the polymer chains remains challenging. Additionally, sulfonating agents are most often used in large excess, which prevents precise control over the degree of sulfonation of aromatic polymers and their functionality. Herein, we address these challenges using 1,3-disulfonic acid imidazolium chloride ([Dsim]Cl), a sulfonic acid-based ionic liquid, to sulfonate aromatic polymers and upgrade plastic waste to electronic materials. We show that stoichiometric [Dsim]Cl can effectively sulfonate model polystyrene up to 92% in high yields, with minimal defects and high regioselectivity for the para position. Owing to its high reactivity, the use of substoichiometric [Dsim]Cl uniquely allows for precise control over the degree of sulfonation of polystyrene. This approach is also applicable to a wide range of aromatic polymers, including waste plastic. To prove the utility of our approach, samples of poly(styrene sulfonate) (PSS), obtained from either partially sulfonated polystyrene or expanded polystyrene waste, are used as scaffolds for poly(3,4-ethylenedioxythiophene) (PEDOT) to form the ubiquitous conductive material PEDOT:PSS. PEDOT:PSS from plastic waste is subsequently integrated into organic electrochemical transistors (OECTs) or as a hole transport layer (HTL) in a hybrid solar cell and shows the same performance as commercial PEDOT:PSS. This imidazolium-mediated approach to precisely sulfonating aromatic polymers provides a pathway toward upgrading postconsumer plastic waste to high-value electronic materials.

The Effect of Renastart Formula Supplementation in Serum Electrolytes in Children with Acute Kidney Injury

Abstract Background patients of renal disease suffer from electrolyte disturbances including hyperkalemia, hyperphosphatemia, hyponatremia, hypocalcemia and hypermagnesemia. Unfortunately, patients with kidney disease require close monitoring for serum electrolytes to maintain normal levels; with traditional nutritional interventions they may need receiving potassium and phosphorus binders Aim: This study will concentrate on the effect and tolerability of Renastart formula supplementation on correction and maintaining serum levels of electrolytes in AKI or AKI on top of CKD pediatric patients. Methods Double arm clinical convenient trial, conducted in Pediatric Nephrology Unit,Ain Shams University, Cairo, Egypt, where 24 participants who had AKI or AKI on top of CKD with hyperphosphatemia and / or hyperkalemia were recruited, the mean of age of participants was 4.1±3.15 years ranged from 0.5 to 10 years. Subjects were divided into two groups, 12 patients per group (group A received a calcium carbonate (phosphorus binder) (9 patients) with dosage 45-65 mg/kg/day orally alone or withsodium polystyrene sulfonate (potassium binder) (11 patients) with dosage 0.5-1mg/kg/day oral and group B received Renastart formula supplemented with breast milk, standard infant formula or diet), the dosage ratio was adjusted to be 1:3 (Renastart was 1/4 daily caloric intake) if serum potassium level ≥5.5 - <6 meq/L and / or serum phosphorus > 7mg/dl. But, if potassium level was ≥ 6 meq/L, the ratio was 1:1 (Renastart was ½ daily caloric intake). Readjusting dosage ratio was according to serum electrolyte levels response for treatment. Follow up of serum levels of potassium was every day until its serum level returned to normal then every month for three months and serum phosphorus was every month for three consecutive months. Results All the included subjects in both groups had high serum potassium (> 5.5 meq/L) and / or high serum phosphorus (>7 mg/dl) upon enrollment, mean serum potassium and serum phosphorus were (5.7±0.41 meq/L) (7.2±1.6 mg/dl) respectively. Regarding the decrease of serum potassium, Renastart formula supplementation in group B and potassium binders in group A resulted in equal decrease in serum potassium levels; Potassium after 3 months of management in group B was (4.22±0.28 mEq/L) (p value between 3rd month- baseline month in group B p < 0.01) and potassium binders in group A (4.48±0.27 mEq/L) (p value between 3rd month – baseline month in group A p < 0.01). Renastart formula in group B ((potassium after 1 month of management = 4.7±0.32 meq/L) (p value between 1st month – baseline month in group B p < 0.01)) had more rapid effect than potassium binders in group A during 1st month of the study ((potassium after 1 month of management =5.1±0.41 meq/L) (p value between 1st month – baseline month in group A p > 0.05). Regarding decrease in serum phosphorus, Renastart formula supplementation in group B resulted in more decrease in serum phosphorus levels though both showed significant drop in phosphorus level (( serum phosphorus after 3 months of management = 4.60±0.29 mg/dl (p value between 3rd month – baseline month in group B p = 0.002)) in comparison to that achieved by phosphorus binders in group A ((5.21±0.29mg/dl) (p value between 3rd month – baseline month in group A p = 0.01)), moreover Renastart supplementation in group B was more rapid than phosphorus binders in group A in decrease serum phosphorus (p value between 1st month and baseline in group B p = 0.002) (p value between 1st month and baseline in group A p = 0.17) Conclusion We can conclude that Renastart formula supplementation was more rapid than potassium binders in decreasing serum potassium levels in AKI pediatric patients, moreover more effective and rapid than phosphorus binders in decreasing serum phosphorus.

A nanofluidic spiking synapse

Currently, the nanofluidic synapse can only perform basic neuromorphic pulse patterns. One immediate problem that needs to be addressed to further its capability of brain-like computing is the realization of a nanofluidic spiking device. Here, we report the use of a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate membrane to achieve bionic ionic current-induced spiking. In addition to the simulation of various electrical pulse patterns, our synapse could produce transmembrane ionic current-induced spiking, which is highly analogous to biological action potentials with similar phases and excitability. Moreover, the spiking properties could be modulated by ions and neurochemicals. We expect that this work could contribute to biomimetic spiking computing in solution.

Kinetic aspects of salinity stability of layer-by-layer polyelectrolyte nanofiltration membranes: Impact of soaking time, types of ions and crosslinking

Recent discovery of very high selectivity of Layer-by-Layer (LBL) nanofiltration (NF) membranes for mono/bivalent ions has attracted significant attention, especially for extraction of lithium from salt lake brines. Besides the exceptionally high selectivity, the salinity stability in highly saline solutions (HSS) that often occurred during NF has been largely neglected. Intuitively, because the LBL membranes are assembled in a saline background solution, the assembly disassembles in highly saline environments. To verify above argument, we reported here a comprehensive study on the performance of polystyrene sulfonate (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) and PSS/poly(allylamine) hydrochloride (PAH) LBL NF membranes in HSS by short/long term immersion and dynamic filtration. Greater binding strength of (PSS/PAH)2.5 corresponded to better salinity stability than (PSS/PDADMAC)2.5. Adsorption bridging of divalent Mg2+ with PSS altered PSS conformation and narrowing the pore size distribution. Compared to static immersion, dynamic filtration accelerated the loss of PEs from (PSS/PAH)2.5 at cLiCl = 2 mol/L, but membrane stability was improved by chemical crosslinking. This research highlighted the kinetic aspects in salinity stability and the chemical-physical behavior of polyelectrolyte complexes (PECs) in HSS. The results offer valuable insights for development of LBL NF membranes for ion separation and resource recovery.

Electrical Interface Parameters of PEDOT:PSS: Effect of Electrodeposition Charge Evaluated Under Body Conditions for Neural Electrode Applications

This study explores the influence of the deposition charge of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) on its electrical interface parameters. For this purpose, PEDOT:PSS was fabricated by electrodeposition on commercial platinum electrodes with the time limited by different charges (1, 3, 6, 9 mC). Further, the electrodes were characterized regarding their electrical interface such as interfacial impedance, potential window, double-layer capacitance, charge storage capacity, and current injection limit under simulated body conditions. The work showed whether and to what extent the change of deposition charge affected the electrical interface parameters of PEDOT:PSS-based platinum electrodes. The electrodes polymerized with 9 mC exhibited a significant increase in specific capacitance, indicating enhanced charge storage capacity. Additionally, this sample demonstrated lower resistance in phosphate-buffered saline, suggesting improved conductivity.

PEDOT:PSS-Based Prolonged Long-Term Decay Synaptic OECT with Proton-Permeable Material, Nafion.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), a conductive polymer, has gained popularity as the channel layer in organic electrochemical transistors (OECTs) due to its high conductivity and straightforward processing. However, difficulties arise in controlling its conductivity through gate voltage, presenting a challenge. To address this issue, aromatic amidine base, diazabicyclo[4.3.0]non-5-ene (DBN), is used to stabilize the doping state of the PEDOT chain through a reliable chemical de-doping process. Furthermore, the addition of the proton-penetrable material Nafion to the PEDOT:PSS channel layer induces phase separation between the substances. By utilizing a solution containing both PEDOT:PSS and Nafion as the channel layer of OECTs, the efficiency of ion movement into the channel from the electrolyte is enhanced, resulting in improved OECT performance. The inclusion of Nafion in the OECTs' channel layer modifies ion movement dynamics, allowing for the adjustment of synaptic properties such as pulse-paired facilitation, memory level, short-term plasticity, and long-term plasticity. This research aims to introduce new possibilities in the field of neuromorphic computing and contribute to biomimetic technology through the enhancement of electronic component performance.

The lifetime improvement of organic light‐emitting diodes with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate on indium‐tin‐oxide surface and deuterated dopant in emitting layer

AbstractIn this study, the PEDOT:PSS conductive polymer material was spin‐coated on the ITO surface to improve the surface roughness of the ITO and reduce the spikes on the ITO surface, so as to avoid the burning spots generated in the green organic light emitting diode (OLED) when the voltage was applied to light it up. The OLED emitting is successfully survived. Deuterium atoms (isotopes of hydrogen) with heavier atomic weights can strengthen C‐D bonds, slow down the kinetic rate for unwarranted chemical reactions, and improve the performance and stability of OLEDs. In this study, deuterated D‐Ir (mppy)3 was employed as the dopant in the emitting layer of green OLED to replace the general Ir (mppy)3 to improve the optoelectronic properties and extend the lifetime of green OLED. At a constant voltage of 4 V, the initial luminance and half lifetime of general Ir (mppy)3 doped and deuterated D‐Ir (mppy)3 doped OLEDs are 188.1 cd/m2, 7.2 h and 438.3 cd/m2, 42.8 h, respectively. It is shown that doping the deuterated D‐Ir (mppy)3 material in the emitting layer has the effect of prolonging the lifetime of OLED. Compared with the general Ir (mppy)3, the lifetime of deuterated D‐Ir (mppy)3 doped OLED achieved an extension by 5.9 times.

Fabrication of ternary hybrid composites of Co-MOFs/MoS2/PEDOTs for sensitive detection of dopamine and norepinephrine in biological samples

In this study, a simple and multifunctional application for Co-based organic frameworks (Co-MOFs) with molybdenum disulfide (MoS2) and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOTs:PSS) is presented. The Co-MOFs with MoS2 exhibit excellent peroxidase mimicking and catalytic activities, making them suitable for colorimetric dopamine sensors. From an electrochemical standpoint, fouling-free and selective sensing of dopamine (DA) and norepinephrine (NE) is highly challenging. However, the synergistic effect of morphological tunability of Co-MOFs with hybrid composites of MoS2 and PEDOTs:PSS offers a wide detection concentration range of 2 nM-350 µM for DA and 20 nM-1000 µM for NE, high sensitivity, excellent anti-fouling, facile kinetic rate reaction, and rapid signal response. A high selectivity rate was achieved in the presence of twenty times higher concentrations of a mixture of ascorbic acid, uric acid, and other bio-chemical co-interferents. Interestingly, ultrasensitive detection limits of 0.23 nM and 2.18 nM (S/N = 3) were achieved for DA and NE, enabling the real-time precise detection of cellular concentrations in PC12 living cells, and biological fluid samples with simple dilution pretreatments. Moreover, the sensor demonstrated satisfactory reproducibility and stability. Finally, the morphological and composite activity-based probes can detect neurotransmitter concentrations in real samples beyond the concentration limit, suggesting a potential clinical sensor tool.

All-in-one, gas-permeable, ultrathin, flexible, and self-adhesive epidermal electrode for biopotential recording and muscle theranostics

Epidermal electronics have attracted extensive attention owing to their potential in personal healthcare and human–machine interactions (HMIs). However, their low conductivity and poor ability to conform to the human skin impede their practical application. Herein, a multifunctional flexible dry epidermal electrode for biopotential recording and muscle thermotherapy was developed based a conductive polymer (poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS)). PEDOT:PSS was modified using poly(vinyl alcohol) (PVA) with hydrophobic groups. The electrode is able to self-adhere to human skin through a hydrophobic interaction with the skin. Moreover, the hydrophilic groups can absorb the humidity under the skin and move it by the hydrophobic groups, which allows the electrode exhibits good gas-permeability. The ultrathin electrode conforms well to the topography of the human skin and, thus, can form a stable and intimate interface with it, resulting in a low electrode–skin contact impedance that allows the recording of biopotentials with high quality. Moreover, the electrode exhibits rapid Joule heating performance at a low voltage (up to 53.8 °C in 12 s at 1.5 V), which is suitable for the electrothermal therapy of muscle. On-body measurements confirm that our electrode could detect muscle fatigue via electromyography (EMG) and perform electrothermal therapy to relieve muscle fatigue. This study offers an efficient method for developing all-in-one wearable flexible epidermal electrode for biopotential recording and muscle theranostics.

Development of Optical Nanosensors for Detection of Potassium Ions and Assessment of Their Biocompatibility with Corneal Epithelial Cells.

Imbalance of potassium-ion levels in the body can lead to physiological dysfunctions, which can adversely impact cardiovascular, neurological, and ocular health. Thus, quantitative measurement of potassium ions in a biological system is crucial for personal health monitoring. Nanomaterials can be used to aid in disease diagnosis and monitoring therapies. Optical detection technologies along with molecular probes emitting within the near-infrared (NIR) spectral range are advantageous for biological measurements due to minimal interference from light scattering and autofluorescence within this spectral window. Herein, we report the development of NIR fluorescent nanosensors, which can quantitatively detect potassium ions under biologically relevant conditions. The optical nanosensors were developed by using photoluminescent single-walled carbon nanotubes (SWCNTs) encapsulated in polymers that contain potassium chelating moieties. The nanosensors, polystyrene sulfonate [PSS-SWCNTs, nanosensor 1 (NS1)] or polystyrene-co-polystyrene sulfonate [PS-co-PSS-SWCNTs, nanosensor 2 (NS2)], exhibited dose-dependent optical responses to potassium ion level. The nanosensors demonstrated their biocompatibility via the evaluation of cellular viability, proliferation assays, and expression of cytokeratin 12 in corneal epithelial cells (CEpiCs). Interestingly, the nanosensors' optical characteristics and their responses toward CEpiCs were influenced by encapsulating polymers. NS2 exhibited a 10 times higher fluorescence intensity along with a higher signal-to-noise ratio as compared to NS1. NS2 showed an optical response to potassium ion level in solution within 5 min of addition and a limit of detection of 0.39 mM. Thus, NS2 was used for detailed investigations including potassium ion level detection in serum. NS2 showed a consistent response to potassium ions at the lower millimolar range in serum. These results on optical sensing along with biocompatibility show a great potential for nanotube sensors in biomedical research.

Preparation of Conductive Cellulose Coated with Conductive Polymer and Its Application in the Detection of pH and Characteristic Substances in Sweat.

Rich biological information in sweat provides great potential for health monitoring and management. However, due to the complexity of sweat, the development of environmentally friendly green electronic products is of great significance to the construction of ecological civilization. This study utilized a simple combination of polystyrene sulfonate sodium (PSS) and filter paper (FP) to prepare cellulose materials coated with conductive polymers, developing an electrochemical sensor based on the modified materials. The mechanical and electrochemical properties of the fabricated PSS/FP membrane were optimized by adjusting the feeding dosage of PSS. The realized PSS/FP composite containing 7% PSS displayed good conductivity (9.1 × 10-2 S/m), reducing electric resistance by 99.2% compared with the original FP membrane (6.7 × 10-4 S/m). The stable current of the membrane in simulated sweat under different pH environments is highly correlated with the pH values. Additionally, when the membrane is exposed to simulated sweat with varying ion concentrations, the current signal changes in real time with the concentration variations. The response time averages around 0.3 s.

Efficient Perovskite Solar Cells Enabled by Facile Synthesis of Triphenylamine‐Based Hole‐Transport Material with D–A1–A2 Structure

In perovskite solar cells (PSCs), the selection of the hole‐transport material (HTM) markedly influences both the achievement of high efficiency and overall stability. This study outlines the synthesis of a dopant‐free HTM founded on the donor–acceptor1–acceptor2 (D–A1–A2)‐conjugated structure and its integration into PSCs. The ensuing PSCs showcase a power conversion efficiency of 17.8%, comparable to NiOx inorganic HTM‐based devices and surpassing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate polymeric HTM‐based devices. The efficiency comparable to NiOx is attributed to the efficient hole extraction and transport facilitated by the conjugated π junctions in the specifically designed structure. Furthermore, these devices exhibit enhanced stability, maintaining 95% of their initial performance for 60 d in an N2 atmosphere without encapsulation. The improved stability primarily arises from the hydrophobic nature of the HTM. The larger π‐conjugated molecules lead to a denser film by reducing intermolecular space, effectively retarding water intrusion and providing superior protection to the perovskite layer. Thus, the dopant‐free D–A1–A2 HTM with an extended conjugated π structure not only effectively enhances device efficiency but also substantially improves device stability.