Stable FAPbI3 Perovskite Solar Cells via Alkylammonium Chloride-Mediated Crystallization Control.

α-Phase formamidinium lead iodide (FAPbI3) perovskite solar cells (PSCs) have garnered significant attention, owing to their remarkable efficiency. Methylammonium chloride (MACl), a common additive, is used to control the crystallization of FAPbI3, thereby facilitating the formation of the photoactive α-phase. However, MACl's high volatility raises concerns regarding its stability and potential impact on the stability of the device. In this study, we partially substituted MACl with n-propylammonium chloride (PACl), which has a long alkyl chain, to promote the oriented crystallization of FAPbI3, ultimately forming an δ-phase-free perovskite. The FAPbI3 film containing PACl demonstrates an enhanced photoluminescence intensity and lifetime. Additionally, PACl's presence at grain boundaries acts as a protective layer for the PSCs. Consequently, we achieved a power conversion efficiency (PCE) of 22.4% and exceptional stability. It maintains over 95% of initial PCE for 100 days in an N2 glovebox, over 85% after 100 h of maximum power point tracking, and over 80% after 60 °C thermal aging.

Regulating Functional Groups Enhances the Performance of Flexible Microporous MXene/Bacterial Cellulose Electrodes in Supercapacitors.

Ultrathin MXene-based films exhibit superior conductivity and high capacitance, showing promise as electrodes for flexible supercapacitors. This work describes a simple method to enhance the performance of MXene-based supercapacitors by expanding and stabilizing the interlayer space between MXene flakes while controlling the functional groups to improve the conductivity. Ti3C2Tx MXene flakes are treated with bacterial cellulose (BC) and NaOH to form a composite MXene/BC (A-M/BC) electrode with a microporous interlayer and high surface area (62.47 m2 g-1). Annealing the films at low temperature partially carbonizes BC, increasing the overall electrical conductivity of the films. Improvement in conductivity is also attributed to the reduction of -F, -Cl, and -OH functional groups, leaving -Na and -O functional groups on the surface. As a result, the A-M/BC electrode demonstrates a capacitance of 594 F g-1 at a current density of 1 A g-1 in 3 M H2SO4, which represents a ∼2× increase over similarly processed films without BC (309 F g-1) or pure MXene (298 F g-1). The corresponding device has an energy density of 9.63 Wh kg-1 at a power density of 250 W kg-1. BC is inexpensive and enhances the overall performance of MXene-based film electrodes in electronic devices. This method underscores the importance of functional group regulation in enhancing MXene-based materials for energy storage.

Peptide-Based Flavivirus Biosensors: From Cell Structure to Virological and Serological Detection Methods.

In tropical and developing countries, mosquito-borne diseases by flaviviruses pose a serious threat to public health. Early detection is critical for preventing their spread, but conventional methods are time-consuming and require skilled technicians. Biosensors have been developed to address this issue, but cross-reactivity with other flaviviruses remains a challenge. Peptides are essentially biomaterials used in diagnostics that allow virological and serological techniques to identify flavivirus selectively. This biomaterial originated as a small protein consisting of two to 50 amino acid chains. They offer flexibility in chemical modification and can be easily synthesized and applied to living cells in the engineering process. Peptides could potentially be developed as robust, low-cost, sensitive, and selective receptors for detecting flaviviruses. However, modification and selection of the receptor agents are crucial to determine the effectiveness of binding between the targets and the receptors. This paper addresses two potential peptide nucleic acids (PNAs) and affinity peptides that can detect flavivirus from another target-based biosensor as well as the potential peptide behaviors of flaviviruses. The PNAs detect flaviviruses based on the nucleotide base sequence of the target's virological profile via Watson-Crick base pairing, while the affinity peptides sense the epitope or immunological profile of the targets. Recent developments in the functionalization of peptides for flavivirus biosensors are explored in this Review by division into electrochemical, optical, and other detection methods.

An ultra-sensitive SARS-CoV-2 antigen optical biosensor based on angiotensin converting enzyme 2 (ACE-2) functionalized magnetic-fluorescent silica nanoparticles.

This work reports on the design and synthesis of an angiotensin-converting enzyme 2 (ACE-2) functionalized magnetic fluorescent silica nanoparticles (Fe-FSNP) as a biosensing platform to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen. Iron oxide (Fe3O4) nanoparticles were synthesized via ultrasonic-assisted coprecipitation and then coated with fluorescent silica nanoparticles (FSNP) through thesol-gelmethod forming the Fe-FSNP samples. Silica obtained from local geothermal powerplant was used in this work and Rhodamine B was chosen as the incorporated fluorescent dye, hence this reports for the first time ACE-2 was immobilized on the natural silica surface. The Fe-FSNP nanoparticle consists of a 18-25 nm magnetic core and a silica shell with a thickness of 30 nm as confirmed from the transmission electron microscopy image. Successful surface functionalization of the Fe-FSNP with ACE-2 as bioreceptor was conducted through hydrosylilation reaction and confirmed through the Fourier transform infrared spectroscopy. The detection of SARS-Cov-2 antigen by Fe-FSNP/ACE2 was measured through the change in its maximum fluorescence intensity at 588 nm where fluorescence- quenching had occurred. The biosensing platform showed a rapid response at 30 min with a linear range of 10-6to 10-2µg ml-1. The magnetic-fluorescent properties of the nanoparticle enables an ultra-sensitive detection of SARS-Cov-2 antigen with the limit of detection as low as 2 fg ml-1.

One-Dimensional HKUST-1-Decorated Glassy Carbon Electrode for the Sensitive Electrochemical Immunosensor of NS1 Dengue Virus Serotype-3.

In this work, simple and sensitive detection of dengue virus serotype-3 (DENV-3) antigen was accomplished by a one-dimensional (1D) HKUST-1-functionalized electrochemical sensor. 1D HKUST-1 was synthesized via a coprecipitation method using triethanolamine (TEOA) as pH modulator and structure-directing agent. The structure, morphology, and sensing performance of the HKUST-1-decorated carbon electrode were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). We found that 40 wt% TEOA transforms the octahedron HKUST-1 to the nanorods while maintaining its crystal structure and providing chemical stability. The 1D HKUST-1-decorated carbon electrode successfully detects the antigen in the range of 0.001-10 ng/mL with a detection limit of 0.932 pg/mL. The immunosensor also exhibits remarkable performance in analyzing the antigen in human serum and showed recovery as high as ∼98% with excellent selectivity and reproducibility.

Enhancing Urine Glucose Sensing Performance through the Introduction of Two Dimensional-Transition Metal Dichalcogenides and Gold Nanoparticles into Silver/UiO-66 Chip of Surface Plasmon Resonance.

This work presents a high-performance surface plasmon resonance (SPR)-based biosensor for glucose detection. While adding a metal-organic framework (MOF) layer, UiO-66, to the biosensor improves selectivity and enables direct detection without additional receptors, it does not significantly enhance sensitivity. A SPR-based biosensor is proposed to overcome this limitation by introducing a layer of 2D-transition metal dichalcogenides (2D-TMD) and decorating the UiO-66 structure with gold nanoparticles (UiO-66AuNP). The optical properties of the biosensor for glucose detection in urine are investigated by employing the finite difference time domain (FDTD) method with Kretschmann configuration at a wavelength of 633 nm, and its performance is effectively improved by incorporating 2D-TMD and AuNP layers into the biosensor structure. Notably, the SPR-based biosensor with the decorated UiO-66 layer exhibits a further change in the SPR angle in the presence of glucose-containing urine. Using computational studies, various performance parameters, such as the biosensors' signal-to-noise ratio (SNR) and quality factor (QF), are evaluated in addition to sensitivity. The maximum sensitivity achieved is 309.3°/RIU for the BK7/Ag/PtSe2/WSe2/MoS2/UiO-66AuNP/sensing medium structure. The exceptional performance of the proposed biosensor structure demonstrates its suitability for precise glucose detection in urine while also opening new avenues for developing bioreceptor-free SPR-based sensors.

Surface plasmon resonance biosensor chips integrated with MoS2-MoO3 hybrid microflowers for rapid CFP-10 tuberculosis detection.

This study reports on the modification of surface plasmon resonance (SPR) chips with molybdenum disulfide-molybdenum trioxide (MoS2-MoO3) microflowers to detect the tuberculosis (TB) markers of CFP-10. The MoS2-MoO3 microflowers were prepared by hydrothermal methods with variations in the pH and amount of trisodium citrate (Na3Ct), which were projected to influence the shape and size of microflower particles. The analysis shows that optimum MoS2-MoO3 hybrid microflowers were obtained at neutral pH using 0.5 g Na3Ct. The modified SPR biosensor exhibits a ten times higher response than the bare Au. Moreover, increasing MoS2-MoO3 thickness results in a higher detection response, sensitivity, and a smaller limit of detection (LOD). Using the optimized material composition, the Au/MoS2-MoO3-integrated SPR sensor can demonstrate sensitivity and LOD of 1.005 and 3.45 ng mL-1, respectively. This biosensor also has good selectivity, stability, and reproducibility based on cross-sensitivity characterization with other analytes and repeated measurements on several chips with different storing times and fabrication batch. Therefore, this proposed SPR biosensor possesses high potential to be further developed and applied as a detection technology for CFP-10 in monitoring and diagnosing TB.

Gas-Sensing Mechanisms and Performances of MXenes and MXene-Based Heterostructures.

MXenes are a class of 2D transition-metal carbides, nitrides, and carbonitrides with exceptional properties, including substantial electrical and thermal conductivities, outstanding mechanical strength, and a considerable surface area, rendering them an appealing choice for gas sensors. This manuscript provides a comprehensive analysis of heterostructures based on MXenes employed in gas-sensing applications and focuses on addressing the limited understanding of the sensor mechanisms of MXene-based heterostructures while highlighting their potential to enhance gas-sensing performance. The manuscript begins with a broad overview of gas-sensing mechanisms in both pristine materials and MXene-based heterostructures. Subsequently, it explores various features of MXene-based heterostructures, including their composites with other materials and their prospects for gas-sensing applications. Additionally, the manuscript evaluates different engineering strategies for MXenes and compares their advantages to other materials while discussing the limitations of current state-of-the-art sensors. Ultimately, this review seeks to foster collaboration and knowledge exchange within the field, facilitating the development of high-performance gas sensors based on MXenes.

A morphological study of bicontinuous concentric lamellar silica synthesized at atmospheric pressure and its application as an internal micro-reflector in dye-sensitized solar cells.

KCC-1, a nanostructured silica material with a bicontinuous concentric lamellar (bcl) morphology, provides plenty of functional characteristics, such as an open channel structure, excellent accessibility, and a large surface area. Although bcl silica exhibits various superior properties, studies on its morphology and its application in dye-sensitized solar cells (DSSCs) are still limited. Therefore, this work aims to study the influence of the synthesis time on the morphology of bcl silica. Moreover, we used the synthesized bcl silica as internal micro-reflectors in DSSCs. The bcl silica was synthesized using the reflux method by varying synthesis times. The morphology of bcl silica was observed using FESEM and HRTEM. FESEM images show that bcl silica has bicontinuous lamellar walls arranged concentrically to form spherical particles. As the synthesis time increases, the average particle size of bcl silica increases. The quantization of bcl silica binary images shows that the average lamellar cross-sectional area ratio decreases with increasing synthesis time. The simulation of the Cahn-Hilliard's spinodal decomposition model using MATLAB also describes the lamellar cross-sectional area ratio of bcl silica. In addition, to characterize the FESEM image's texture, a Shannon entropy calculation was performed. The line and circular gray value intensity profiles of the HRTEM image show that bcl silica has a denser core than the outer part. The denser core proves that the lamellae in bcl silica are concentrically arranged towards the particle core. Furthermore, we added bcl silica to a photoanode to see the effect of bcl characteristics on the DSSC performance. The results show that the bcl silica significantly improves the light-harvesting efficiency in DSSCs due to its low refractive index and open channel structure.

Soft-hard interface design in super-elastic conductive polymer hydrogel containing Prussian blue analogues to enable highly efficient electrochemical deionization.

The poor cycling stability of faradaic materials owing to volume expansion and stress concentration during faradaic processes limits their use in large-scale electrochemical deionization (ECDI) applications. Herein, we developed a "soft-hard" interface by introducing conducting polymer hydrogels (CPHs), that is, polyvinyl alcohol/polypyrrole (PVA/PPy), to support the uniform distribution of Prussian blue analogues (e.g., copper hexacyanoferrate (CuHCF)). In this design, the soft buffer layer of the hydrogel effectively alleviates the stress concentration of CuHCF during the ion-intercalation process, and the conductive skeleton of the hydrogel provides charge-transfer pathways for the electrochemical process. Notably, the engineered CuHCF@PVA/PPy demonstrates an excellent salt-adsorption capacity of 22.7 mg g-1 at 10 mA g-1, fast salt-removal rate of 1.68 mg g-1 min-1 at 100 mA g-1, and low energy consumption of 0.49 kW h kg-1. More importantly, the material could maintain cycling stability with 90% capacity retention after 100 cycles, which is in good agreement with in situ X-ray diffraction tests and finite element simulations. This study provides a simple strategy to construct three-dimensional conductive polymer hydrogel structures to improve the desalination capacity and cycling stability of faradaic materials with universality and scalability, which promotes the development of high-performance electrodes for ECDI.

Cinnamoyl Dipyrromethenes as Fluorescence Zinc(II) Ion Sensor.

Friedel-Crafts acylation of dipyrromethane with cinnamoyl chloride was conducted to obtain dicinnamoyl dipyrromethane compounds 3 and 4. Both compounds were subsequently oxidized by DDQ to produce dicinnamoyl dipyrromethene ligands (DC-1 and DC-2). A large bathochromic shift compared to dipyromethene (D) was observed at 95 nm for DC-1 and 67 nm for DC-2. Both compounds showed remarkable chelation-enhanced fluorescence (CHEF) upon addition of zinc(II) ions. Similar to the quadrupolar system, DC-1 exhibited absorption and emission near the optical windows of the tissue. However, asymmetrical DC-2 had a better "turn-on" CHEF, with a fluorescence intensity that was 22 times higher than that of compound D. The DC-2 ligand also showed a limit of detection (LOD) of up to 3.0×10-8  M and selectivity toward zinc(II) ions compared to alkali and alkaline earth metal ions.

The revelation of glucose adsorption mechanisms on hierarchical metal-organic frameworks using a surface plasmon resonance sensor.

The gold layer on the surface plasmon resonance (SPR) sensor chip cannot detect small molecules, such as glucose without the use of specific receptors. Metal-organic frameworks (MOFs) are useful in biosensing technologies for capturing and co-localizing enzymes and receptors with the target biomolecule. In many previous studies, the properties of the MOFs were often ignored, with these studies focusing on the selection of appropriate receptors. To take advantage of the unique properties of MOFs in biosensors, one must also consider the technique and transducer used because these aspects will strongly influence the detection mechanism. In this work, we have investigated for the first time, the applications of hierarchical metal-BDC (M-BDC) MOFs for glucose detection using the SPR technique without the use of specific receptors. The underlying interactions and adsorption mechanisms were analyzed using adsorption isotherm and kinetic models. The sensing measurements show that the SPR chips functionalized with M-BDC MOFs exhibit higher sensitivity and lower limit of detection (LOD). Specifically, the sensitivity follows the order of Zr-BDC > Cu-BDC > Mn-BDC > Ni-BDC > bare Au SPR chips with the LOD in the order of Zr-BDC < Mn-BDC < Ni-BDC < Cu-BDC < bare Au SPR chips. The selectivity test results reveal that Zr-BDC exhibits a decent selectivity to glucose in the presence of other interfering compounds, such as ascorbic acid, uric acid, maltose, and urea. These results demonstrate the promising potential of MOFs for SPR biosensing.

A Perspective on Using Organic Molecules Composing Carbon Dots for Cancer Treatment.

Fluorescent Carbon dots (CDs) derived from biologically active sources have shown enhanced activities compared to their precursors. With their prominent potentiality, these small-sized (<10nm) nanomaterials could be easily synthesized from organic sources either by bottom-up or green approach. Their sources could influence the functional groups present on the CDs surfaces. A crude source of organic molecules has been used to develop fluorescent CDs. In addition, pure organic molecules were also valuable in developing practical CDs. Physiologically responsive interaction of CDs with various cellular receptors is possible due to the robust functionalization on their surface. In this review, we studied various literatures from the past ten years that reported the potential application of carbon dots as alternatives in cancer chemotherapy. The selective cytotoxic nature of some of the CDs towards cancer cell lines suggests the role of surface functional groups towards selective interaction, which results in over-expressed proteins characteristic of cancer cell lines. It could be inferred that cheaply sourced CDs could selectively bind to overexpressed proteins in cancer cells with the ultimate effect of cell death induced by apoptosis. In most cases, CDs-induced apoptosis directly or indirectly follows the mitochondrial pathway. Therefore, these nanosized CDs could serve as alternatives to the current kinds of cancer treatments that are expensive and have numerous side effects.

Contribution of the lamellar morphology to the photocatalytic activity of alkaline-hydrothermally treated titania in rhodamine B photodegradation.

TiO2 particles with a specific morphology are essential for their accessibility and photoactivity. The present study shows that NH4OH-based alkaline-hydrothermal treatment affects the transformation of their particle morphology. We investigated the effect of NH4OH by varying the synthesis route. We observed that the TiO2 particles with an open channel pore structure only resulted in the alkaline-hydrothermally treated and calcined samples. Based on Raman and XRD analyses, we figured out the titanate layers as an intermediate phase resulting from the alkaline-hydrothermal treatment of the amorphous particles. The hydrothermal treatment changed the particle surface morphology into a lamellar structure with a high specific surface area. These are the anatase precursors with {200} planes that transform into the anatase phase after calcination. The calcination followed by alkaline-hydrothermal treatment converted the crystallinity without significantly changing their morphology. We found that the morphology of TiO2 particles can be modified via hydrothermal treatment using NH4OH as long as the particles remain uncrystallized. We suggested the modification of particle morphology through the swelling and phase segregation process by alkaline-hydrothermal treatment. All final products have been used for the photodegradation of rhodamine B. S-HT-500 and A-HT-500 show the best photocatalytic activity with their rate constants (k) of 47.9 and 30.9 × 10-2 min-1, and their surface area-normalized rate constants (ksa) of 6.5 and 2.6 × 10-3 L m-2 min-1, respectively, and have a photocatalytic efficiency of 90.93% and 67.78%, respectively, after 10 minutes of UV irradiation. This activity is approximately 3.5 times and 1.5 times higher than that of Degussa P25; 30 times and 20 times higher than that without a photocatalyst.

The Potential of Double-Faced Polyester-Viscose Woven Fabric as a Porous Substrate for Direct-Coating and Multilayer Concept.

Textile-based sensors fabricated using the direct-coating method are the appropriate choice to meet the aspects of flexibility, non-invasiveness, and lightness for continuous monitoring of the human body. The characteristics of the sensor substrate are directly influenced by factors such as the type of weave, thread fineness, fabric density, and the type of polymeric constituent fibers. The fabric used as the sensor substrate, fabricated using the direct-coating method, must be capable of retaining the electrode paste solution, which has higher viscosity, on one surface of the fabric to avoid short circuits during the fabrication process. However, during its application, this fabric should allow the easy passage of analyte solutions with low viscosity as much as possible. Hence, an appropriate fabric construction is required to serve as the substrate for textile-based sensors to ensure the success of the fabrication process and the effectiveness of the resulting sensor's performance. The development of the structural design of the fabric to be used as a substrate for non-invasive biosensors with a multilayer concept is carried out by weaving and sewing processes utilizing polyester-viscose fibers. During the production process, variations are applied, such as weft yarn density, the characterization of wetting time, absorption rate, maximum wetted radius, spreading speed, and accumulative one-way transport index. The most suitable fabric for use as a substrate for non-invasive biosensors with a multilayer concept, such as in this research, is a fabric with a weft thread density of 70 strands per inch, along with the addition of an analyte transfer thread configuration.

Development of a Single-Chain Variable Fragment of CR3022 for a Plasmonic-Based Biosensor Targeting the SARS-CoV-2 Spike Protein.

Two years after SARS-CoV-2 caused the first case of COVID-19, we are now in the "new normal" period, where people's activity has bounced back, followed by the easing of travel policy restrictions. The lesson learned is that the wide availability of accurate and rapid testing procedures is crucial to overcome possible outbreaks in the future. Therefore, many laboratories worldwide have been racing to develop a new point-of-care diagnostic test. To aid continuous innovation, we developed a plasmonic-based biosensor designed explicitly for portable Surface Plasmon Resonance (SPR). In this study, we designed a single chain variable fragment (scFv) from the CR3022 antibody with a particular linker that inserted a cysteine residue at the second position. It caused the linker to have a strong affinity to the gold surface through thiol-coupling and possibly become a ready-to-use bioreceptor toward a portable SPR gold chip without purification steps. The theoretical affinity of this scFv on spike protein was -64.7 kcal/mol, computed using the Molecular Mechanics Generalized Born Surface Area (MM/GBSA) method from the 100 ns molecular dynamics trajectory. Furthermore, the scFv was produced in Escherichia coli BL21 (DE3) as a soluble protein. The binding activity toward Spike Receptor Binding Domain (RBD) SARS-CoV-2 was confirmed with a spot-test, and the experimental binding free energy of -10.82 kcal/mol was determined using portable SPR spectroscopy. We hope this study will be useful in designing specific and low-cost bioreceptors, particularly early in an outbreak when the information on antibody capture is still limited.

Facile and controllable synthesis of monodisperse gold nanoparticle bipyramid for electrochemical dopamine sensor.

We demonstrated potential features of gold nanoparticle bipyramid (AuNB) for an electrochemical biosensor. The facile synthesis method and controllable shape and size of the AuNB are achieved through the optimization of cetyltrimethylammonium chloride (CTAC) surfactant over citric acid (CA) ratio determining the control of typically spherical Au seed size and its transition into a penta-twinned crystal structure. We observe that the optimized ratio of CTAC and CA facilitates flocculation control in which Au seeds with size as tiny as ∼14.8 nm could be attained and finally transformed into AuNB structures with an average length of ∼55 nm with high reproducibility. To improve the electrochemical sensing performance of a screen-printed carbon electrode, surface modification with AuNB via distinctive linking procedures effectively enhanced the electroactive surface area by 40%. Carried out for the detection of dopamine, a neurotransmitter frequently linked to the risk of Parkinson's, Alzheimer's, and Huntington's diseases, the AuNB decorated-carbon electrode shows outstanding electrocatalytic activity that improves sensing performance, including high sensitivity, low detection limit, wide dynamic range, high selectivity against different analytes, such as ascorbic acid, uric acid and urea, and excellent reproducibility.

Nitrogen and Sulfur Co-Doped Hierarchically Porous Carbon Nanotubes for Fast Potassium Ion Storage.

Exploration of advanced carbon anode material is the key to circumventing the sluggish kinetics and poor rate capability for potassium ion storage. Herein, a synergistic synthetic strategy of engineering both surface and structure is adopted to design N, S co-doped carbon nanotubes (NS-CNTs). The as-designed NS-CNTs exhibit unique features of defective carbon surface, hollow tubular channel, and enlarged interlayer space. These features significantly contribute to a large potassium storage capacity of 307 mA h g-1 at 1 A g-1 and a remarkable rate performance with a capacity of 151 mA h g-1 even at 5 A g-1 . Furthermore, an excellent cyclability with 98% capacity retention after 500 cycles at 2 A g-1 is also achieved. Systematic analysis by in situ Raman spectroscopy and ex situ TEM demonstrates the structural stability and reversibility in the charge-discharge process. Although the kinetics studies reveal the capacitive-dominated process for potassium storage, density functional theory calculations provide evidence that N, S co-doping contributes to expanding the interlayer space to promote the K-ion insertion, improving the electronic conductivity, and providing ample defective sites to favor the K-ion adsorption.

Optimized antibody immobilization on natural silica-based nanostructures for the selective detection of E. coli.

This study reports for the first time the surface modification of fluorescent nanoparticles derived from geothermal silica precipitate with Escherichia coli (E. coli) antibody. The immobilization of biomolecules on the inorganic surface has been carried out using two different pathways, namely the silanization and hydrosilylation reactions. The former applied (3-aminopropyl)triethoxysilane (APTES) as the crosslinker, while the latter used N-hydroxysuccinimide coupled with N-ethyl-N'-(3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC/NHS). Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), and fluorescence spectroscopy were used to confirm the chemical, physical, and optical properties of the surface-modified fluorescent silica nanoparticles (FSNPs). Based on the results of the FTIR, fluorescence spectroscopy and stability tests, the modified FSNPs with EDC/NHS with a ratio of 4 : 1 were proven to provide the optimum results for further conjugation with antibodies, affording the FSNP-Ab2 sample. The FSNP-Ab2 sample was further tested as a nanoplatform for the fluorescence-quenching detection of E. coli, which provided a linear range of 102 to 107 CFU mL-1 for E. coli with a limit of detection (LoD) of 1.6 × 102 CFU mL-1. The selectivity of the biosensor was observed to be excellent for E. coli compared to that for P. aeruginosa and S. typhimurium, with reductions in the maximum fluorescence intensity at 588 nm of 89.22%, 26.23%, and 54.06%, respectively. The inorganic nanostructure-biomolecule conjugation with optimized coupling agents showed promising analytical performance as a selective nanoplatform for detecting E. coli bacteria.

Performance of PEDOTOH/PEO-based Supercapacitors in Agarose Gel Electrolyte.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a prime example of conducting polymer materials for supercapacitor electrodes that offer ease of processability and sophisticated chemical stability during operation and storage in aqueous environments. Yet, continuous improvement of its electrochemical capacitance and stability upon long cycles remains a major interest in the field, such as developing PEDOT-based composites. This work evaluates the electrochemical performances of hydroxymethyl PEDOT (PEDOTOH) coupled with hydrogel additives, namely poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA), and polyethyleneimine (PEI), fabricated via a single-step electrochemical polymerization method in an aqueous solution. The PEDOTOH/PEO composite exhibits the highest capacitance (195.2 F g-1 ) compared to pristine PEDOTOH (153.9 F g-1 ), PEDOTOH/PAA (129.9 F g-1 ), and PEDOTOH/PEI (142.3 F g-1 ) at a scan rate of 10 mV s-1 . The PEDOTOH/PEO electrodes were then assembled into a symmetrical supercapacitor in an agarose gel. The type of supporting electrolytes and salt concentrations were further examined to identify the optimal agarose-based gel electrolyte. The supercapacitors comprising 2 M agarose-LiClO4 achieved a specific capacitance of 27.6 F g-1 at a current density of 2 A g-1 , a capacitance retention of ∼94% after 10,000 charge/discharge cycles at 10.6 A g-1 , delivering a maximum energy and power densities of 11.2 Wh kg-1 and 17.28 kW kg-1 , respectively. The performance of the proposed supercapacitor outperformed several reported PEDOT-based supercapacitors, including PEDOT/carbon fiber, PEDOT/CNT, and PEDOT/graphene composites. This study provides insights into the effect of incorporated hydrogel in the PEDOTOH network and the optimal conditions of agarose-based gel electrolytes for high-performance PEDOT-based supercapacitor devices.