Study of Chemical Polymerization of Polypyrrole with SDS Soft Template: Physical, Chemical, and Electrical Properties

Polypyrrole (PPy) is a conductive polymer known for its biocompatibility and ease of synthesis. Chemically polymerized PPy was synthesized in the presence of sodium dodecyl sulfate (SDS), showing correlations among chemical properties, physical morphology, and electrical properties. Focused synthesis parameters included the pyrrole (Py) concentration, SDS concentration, and ammonium persulfate (APS)/Py ratio. The addition of SDS during chemical polymerization influenced the physical morphology of PPy by altering the self-assembling process via micelle formation, yielding sheet-like morphologies. However, the phenomenon also relied heavily on other synthesis parameters. Varying SDS concentrations within the 0.01 to 0.30 M window produced PPy sheets with no significant difference in optical band gap or physical size. While using 0.10 M SDS, an increase in Py concentration from 0.10 to 0.30 M yielded a larger size of PPy as the morphology changed from sheet-like to irregular shape. The band gap dropped from 2.35 to 1.10 eV, and the conductivity rose from 6.80 × 10–1 to 9.40 × 10–1 S/m. With an increase in the APS/Py ratio, the PPy product changed from a random to a sheet-like form. The product provided a larger average size, a decreased band gap, and increased electrical conductivity. Py polymerization in the absence of SDS revealed no significant change in shape or size as the Py concentration increased from 0.10 to 0.30 M; only a sphere-like form was observed, with a large band gap and small conductivity. Results from Raman spectral analysis indicated a correlation between optical band gap, physical morphology, and bipolaron/polaron ratio, mainly at the wavelengths associated with C–C stretching and C–H deformation. The increase in average size was associated with a decrease in band gap and resistance as well as an increase in the bipolaron/polaron ratio. This work indicates a strong correlation between size, morphology, electrical properties, and the bipolaron/polaron ratio of PPy in the presence of SDS

Single-Walled Carbon Nanotube–Poly(porphyrin) Hybrid for Volatile Organic Compounds Detection

Porphyrins due to their unique and interesting physicochemical properties have been widely investigated as functional materials for chemical sensor fabrication. However, their poor conductivity is a major limitation toward the realization of porphyrin-based field-effect transistor/chemiresistor sensor. The issue of conductivity can be overcome by exploiting the excellent electrical property of single-walled carbon nanotubes (SWNTs) to make a SWNTs-based hybrid device in which SWNTs would act as a transducer and porphyrin as a sensory layer. The present attempt was to fabricate a SWNTs–poly­(tetraphenylporphyrin) hybrid through electrochemical route and to evaluate its potential as a low-power chemiresistor sensor for sensing acetone vapor as a model for volatile organic compounds. Functionalization of SWNTs with porphyrin polymer by the electrochemical method resulted in a fuller coverage of SWNTs surface compared to a partial coverage by adsorption and thereby higher sensitivity. SWNTs were coated with poly­(tetraphenylporphyrin) of different thickness by applying different charge density to optimize sensing performance. Differences in sensing performance were noticed for hybrids fabricated at varying charge densities, and the optimum sensing response was found at 19.65 mC/cm². The hybrid exhibited a wide dynamic range for acetone vapor sensing from 50 to ∼230 000 ppm with a limit of detection of 9 ppm. The field-effect transistor studies showed a negative threshold voltage shift and almost constant transconductance when exposed to air/analyte, indicating electrostatic gating dominated sensing mechanism. Further, the results confirmed a good stability of the device over a period of 180 days. The long-term device stability along with the sensing capability at low analyte concentration with a wide dynamic range and easily scalable fabrication technique signify the potential of SWNT–poly­(porphyrin) hybrid for volatile organic compound sensing applications

One-Step Hydrothermal Synthesis of Precious Metal-Doped Titanium Dioxide–Graphene Oxide Composites for Photocatalytic Conversion of CO₂ to Ethanol

We utilized a one-step hydrothermal process for the synthesis of precious metal-doped titanium dioxide (TiO2)/graphene oxide (GO) composites. The metal-doped TiO2/GO composites, including silver–TiO2/GO (Ag–TiO2/GO), palladium–TiO2/GO (Pd–TiO2/GO), and copper–TiO2/GO (Cu–TiO2/GO), were synthesized by mixing a metal precursor, titanium butoxide, and graphene oxide in a water–ethanol mixture in an autoclave hydrothermal reactor. The photocatalytic performance of the composites was tested in the photoreduction of carbon dioxide (CO2) to ethanol. Ag–TiO2/GO, Pd–TiO2/GO, and Cu–TiO2/GO exhibited an ethanol production rate of 109, 125, and 233 μmol/gcat h, respectively. The outstanding performances of Cu–TiO2/GO can be attributed to a combined effect of key parameters, including optical band gap, crystallite size, and BET surface area

Electrochemical Sensor Based on a Composite of Reduced Graphene Oxide and Molecularly Imprinted Copolymer of Polyaniline–Poly(<i>o</i>‑phenylenediamine) for Ciprofloxacin Determination: Fabrication, Characterization, and Performance Evaluation

Contamination of antibiotics in water is a major cause of antibiotic resistance (ABR) in pathogens that endangers human health and food security worldwide. Ciprofloxacin (CIP) is a synthetic fluoroquinolone (FQ) antibiotic and is reportedly present in surface water at a concentration exceeding the ecotoxicological predicted no-effect concentration in some areas. This study fabricated a CIP sensor using an electropolymerized molecularly imprinted polymer (MIP) of polyaniline (PANI) and poly(o-phenylenediamine) (o-PDA) with CIP recognition sites. The MIP was coated on a reduced graphene oxide (rGO)-modified glassy carbon electrode (rGO/GCE) and operated under a differential pulse voltammetry (DPV) mode for CIP detection. The sensor exhibited an excellent response from 1.0 × 10–9 to 5.0 × 10–7 mol L–1 CIP, showing a sensor detection limit and sensitivity of 5.28 × 10–11 mol L–1 and 5.78 μA mol–1 L, respectively. The sensor’s sensitivity for CIP was 1.5 times higher than that of the other tested antibiotics, including enrofloxacin (ENR), ofloxacin (OFX), sulfamethoxazole (SMZ), and piperacillin sodium salt (PIP). The reproducibility and reusability of the sensor devices were also studied

Alkanolamine-Grafted and Copper-Doped Titanium Dioxide Nanosheets–Graphene Composite Heterostructure for CO₂ Photoreduction

CO2 photoreduction is an intriguing approach to carbon capture, utilization, and storage (CCUS). It relies on an effective photocatalyst to generate photoinduced electrons that incorporate carbon dioxide (CO2), yielding fuel products, e.g., methane, methanol, and ethanol. The heterostructure of titanium dioxide nanosheets (TNS) and graphene oxide (GO) is a sandwich-type composite consisting of two 2-dimensional nanostructures (2D–2D). It was demonstrated as an excellent candidate for CO2 photoreduction due to its outstanding charge separation ability. This research studied the photoactivity of alkanolamine-grafted TNS and alkanolamine-grafted and copper-doped TNS/GO composites. In the first experiment, triethanolamine-grafted TNS (TEA–TNS) exhibited the best ability in CO2 photoreduction compared to monoethanolamine- and diethanolamine-grafted TNS (MEA–TNS and DEA–TNS) due to the base-catalyzed hydration nature of CO2–TEA interactions. In the second experiment, we studied the photoactivity of four composites, including copper-doped TNS/GO (Cu-TNS/GO), TEA-[Cu-TNS/GO] (grafting TEA on Cu-TNS/GO), Cu-[TEA-TNS]/GO (doping Cu on TEA-TNS/GO), and TEA-Cu-TNS/GO (one-step hydrothermal synthesis with the Cu precursor, TEA, and GO). TEA-[Cu-TNS/GO] showed the best photoactivity since TEA was added last to the heterostructures, which benefited in avoiding side chelation reactions between TEA and Cu ions and ensuring TEA exposure to CO2