Polyaniline Nanoparticles Research Articles

Electrochemical and quantum chemical study of polyaniline nanoparticles suspension in HCl and H2SO4

The electrochemical behavior of nanopolyaniline (nPANI) particles dispersed as a stable phase in HCl and H2SO4 solutions on a gold electrode was studied and compared using cyclic voltammetry (CV) and chronoamperometry methods. The electrochemical results showed two irreversible-redox conversions within the polyaniline structure which are controlled by the adsorption and diffusion mechanism of nPANI particles. The total numbers of redox active sites per nPANI particle were determined using CV and chronoamperometry methods. The Langmuir adsorption isotherm was used to describe the adsorption process, and the corresponding adsorption parameters (θmax and ΔGads) were calculated. The quantum chemical calculations and Monte Carlo simulation demonstrated that polyaniline as a macro molecule enables to replace water and acid molecules from the surface upon its adsorption to the gold substrate. The surface analysis of the electrode using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy demonstrated the adsorption of nPANI particles. Moreover, both experimental and simulation results confirmed that the adsorption of nPANI-HCl particles is higher than nPANI-H2SO4 particles.

Electrochemical Nanocomposite Single-Use Sensor for Dopamine Detection.

In this work, we report the development of a simple and sensitive sensor based on graphite screen-printed electrodes (GSPEs) modified by a nanocomposite film for dopamine (DA) detection. The sensor was realized by electrodepositing polyaniline (PANI) and gold nanoparticles (AuNPs) onto the graphite working electrode. The sensor surface was fully characterized by means of the cyclic voltammetry (CV) technique using [Fe(CN)6]4−/3− and [Ru(NH3)6]2+/3+ as redox probes. The electrochemical behavior of the nanocomposite sensor towards DA oxidation was assessed by differential pulse voltammetry (DPV) in phosphate buffer saline at physiological pH. The sensor response was found to be linearly related to DA concentration in the range 1–100 μM DA, with a limit of detection of 0.86 μM. The performance of the sensor in terms of reproducibility and selectivity was also studied. Finally, the sensor was successfully applied for a preliminary DA determination in human serum samples.

Fabrication of mixed matrix anion exchange membrane decorated with polyaniline nanoparticles to chloride and sulfate ions removal from water

A heterogeneous anion exchange membrane was modified by introducing polyaniline nanoparticles, in order to enhance its electrochemical properties in view of chloride and sulfate ion removal from water. Polyaniline nanoparticles were synthesized by facile chemical polymerization technique. Nanoparticles were characterized by FTIR, FESEM, and XRD. In addition, SOM images showed a uniform surface for membranes. Utilizing PANI nanoparticles in membrane body led to increase of water content, ion exchange capacity, surface hydrophilicity, and electrical conductivity. Membrane transport number and permselectivity were improved in NaCl solution by incorporating PANI nanoparticles; in Na2SO4 solution, they showed an opposite trend. The chloride and sulfate flux were enhanced by a low PANI concentration and declined at higher concentration. Modified PANI membranes showed a lower selectivity and flux for bivalent ions compared to monovalent ions. Membrane mechanical resistance was increased by using PANI in concentrations up to 2 wt% and decreased at higher PANI ratios.

Surface modification of sulfonated polyethersulfone membrane with polyaniline nanoparticles for application in direct methanol fuel cell

A novel polyion nanocomposite membrane was synthesized by doping the surface and matrix of sulfonated polyethersulfone (SPES) with polyaniline (PANi) nanoparticles to facilitate proton conduction in direct methanol fuel cell (DMFC) application. The synthesized membrane exhibited effective, ionic interaction, dense morphology with high thermal stability, adequate tensile strength (60 Mpa) and considerable ion exchange capacity (2.2 meq g−1). The membrane exhibited low methanol permeability of 7.46 × 10−8 cm2s−1 with high proton conductivity (0.098 Scm−1) besides adequate hydrolytic and oxidative stabilities. A maximum power density of 99 mWcm−2 at a current density of 250 mAcm−2 was obtained with a single slice fuel cell setup. Molecular dynamics simulation based on the COMPASS force-field was applied to investigate the influence of PANi nanoparticles, temperature and hydration level on the diffusivity of hydronium ions. Rapid mass transfer of hydronium ions within the PANi incorporated SPES membrane, could be achieved at higher temperatures and hydration levels. Analysis by radial distribution function (RDF) revealed extensive interactions of sulfonic acid groups of SPES and amine groups of PANi with water molecules. The polyion complex membrane was found to exhibit significant prospect of scale-up for potential application in DMFC.

Fabrication of Novel Printable Electrically Conductive Adhesives (ECAs) with Excellent Conductivity and Stability Enhanced by the Addition of Polyaniline Nanoparticles.

Electrically conductive adhesives (ECAs) are one of the low temperature bonding materials. It can be used to replace toxic Sn-Pb solder. The key issue for the application of ECAs is how to improve their electrical properties. In the present study, we develop an effective method to promote the electrical properties of ECAs by addition of polyaniline (PANI) nanoparticles. PANIs were synthesized via a facile one-step chemical oxidative polymerization method. After adding 0.5 wt% PANI nanoparticles, the conductivity of ECAs increased dramatically by an order of magnitude. The bulk resistivity of 8.8 × 10−5 Ω·cm is achieved for 65 wt% silver fillers with 0.5 wt% PANIs loaded ECAs. Besides, this improvement has no negative effect on the shear strength and the aging life of ECAs. Moreover, the use of PANIs not only lowers the percolation threshold of ECAs, but also reduces the cost and improves the bonding reliability. Finally, PANIs enhanced ECAs patterns were successfully printed by a stencil printing method, which proved their potential applications in replacing conventional solder pastes and printing functional circuits.

Role of the Structure of Graphene Oxide Sheets on the CO2 Adsorption Properties of Nanocomposites Based on Graphene Oxide and Polyaniline or Fe3O4-Nanoparticles

New nanocomposites based on graphene oxide with polyaniline (PANI) or Fe3O4 nanoparticles (MG) were synthesized for CO2 capture. To study the effect of graphene oxide structure on the CO2 retention...

Dynamic Electrochemistry of Polyaniline Nanoparticle Dispersions

Solid electroactive nanoparticles could be electrochemically oxidized/reduced at solid electrodes, transferring large amounts of charge. Therefore, concentrated dispersions of particles could be used in flow batteries. [1] While an extensive experimental and theoretical work has been made on the electrochemistry of single small nanoparticles (nanoimpact regime)[2], the dynamic electrochemical behavior of large ensembles of electroactive nanoparticles has not been studied. In the present work we describe the experimental study of different dispersions of polyaniline nanoparticles. Polyaniline is a well-known material for conventional batteries.[3] It is shown that nanoparticle adsorption occurs in glassy carbon electrodes. Besides, the charging/discharging of the nanoparticle dispersion is controlled by the combined effect of the nanoparticle diffusion in the electrolyte (which controls the residence time in contact with the electrode) and the charge diffusion inside the nanoparticle (which control the single particle charging/discharging). While small nanoparticles can be changed in a short time, the residence time is also limited due to the larger diffusion coefficient. Therefore, a maximum efficiency of conversion is observed. Moreover, the conversion efficiency could be increased by increasing the viscosity of the electrolytes. On the other hand, the efficiency could be largely increased by introducing a redox mediator which shuttle the charge between the dispersed nanoparticles and the solid electrode. The relevance of the rate of charging/discharging towards the flow battery applications will be discussed. References Z. Qi and G.M. Koenig, J. Vac. Sci. Technol. B. 35, 40801:1-27, 2017.E. Katelhon, et al, J. Phys. Chem. C. 120, 17029-17034, 2016 and refs therein.C. Barbero, et al, J. Mater. Chem., 4, 1775-1783, 1994.

Investigation of thermodynamical, dielectric and electro-optical parameters of nematic liquid crystal doped with polyaniline and silver nanoparticles

In the present investigation, thermo-dynamical, dielectric & electro-optical characterization of a neamtic liquid crystal (NLC) and its mixtures with polyaniline (PANI) & silver nanoparticles (Ag NPs) have been carried out. To visualize the combined effect of polyaniline and silver nanoparticles, a polyaniline/silver nanocomposite has been prepared. Equal concentration of polyaniline, silver nanoparticles & polyaniline/silver nanocomposite has been taken and doped into the pure NLC material. A comparison of various LC parameters of pure NLC material and its mixtures with different dopant has also been done. Thermodynamical study suggests that the presence of polymer and nanoparticles duo in LC can tune the order parameter of LC material. Dielectric measurements have been performed to obtain the dielectric permittivity, dielectric anisotropy, and ac conductivity values. The birefringence of the mixtures has been measured to reveal the role of guest entity on the electro-optical properties of LC material. From the experimental values, it can be concluded that the polyaniline/silver nanocomopsite doped LC mixture can be utilized in enhancing the features of liquid crystal displays & other energy efficient devices.

Investigation of the electrical charge transport mechanism and magnetoresistance response in chloride-doped polyaniline–Fe composite nanofibers

One-dimensional composite nanostructures of chloride-doped polyaniline (PANI-Cl) and Fe nanoparticles (NPs) were fabricated via deposition of Fe NPs onto the PANI nanofiber matrix at room temperature. Morphological and structural characterization performed using microscopic techniques, e.g. scanning electron microscopy and transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy confirmed effective deposition of crystalline Fe NPs onto the amorphous PANI-Cl nanofiber matrix. The temperature-dependent magnetic property measurement results revealed the ferromagnetic nature of the prepared PANI-Cl–Fe composite nanofibers (CNFs) structure. Depending on the Fe NP loading, the PANI-Cl–Fe CNFs showed both metallic and semiconducting behaviour. The temperature-dependent resistivity of semiconducting PANI-Cl–Fe CNFs was best described by Efros–Shklovskii variable range hopping (ES-VRH) and Mott three-dimensional variable range hopping (Mott-3D-VRH) mechanisms at low and high temperature regimes. Magnetoresistance (MR) investigation was executed at different temperatures and magnetic fields for the PANI-Cl–Fe CNF pellets in semiconducting form. Room temperature (300 K) negative MR values were detected in both the low and high magnetic field regions. A significant increase in MR values was noted with a decrease in temperature from 300 K to 5 K. Meanwhile, the observed low-field negative MR behaviour of PANI-Cl–Fe CNFs was explained by the forward interference model. Therefore, the implications of these findings might be significant for the application of PANI-Cl–Fe CNFs as sensing materials for magnetic field sensor devices.

Polyaniline nanoparticle coated graphene oxide composite nanoflakes for bifunctional multicolor electrochromic and supercapacitor applications

Graphene oxide (GO)/polyaniline (PANI) composite nanoflakes were fabricated by chemical oxidative polymerization of aniline onto GO nanoflakes. The electrochromic properties and the electrochemical capacitive behaviors of the GO/PANI composite nanoflake film were investigated. The GO/PANI nanocomposite film exhibits excellent electrochromic and supercapacitive performances. In comparison with neat PANI film, the GO/PANI composite nanoflake film shows larger optical modulation, faster response speed, larger coloration efficiency and better cycling stability. Moreover, an areal capacitance of (137 mF/cm2) is obtained for GO/PANI nanoflake film at a scanning rate of 5 mV/s, higher than that of neat PANI film (36 mF/cm2). The GO/PANI composite nanoflake film also shows enhanced electrochromic and supercapacitive durability. And the electrochromism also could be utilized as an indicator for the capacitance. The high-performance GO/PANI nanocomposite film shows promising features for multifunctional devices combining energy storage and electrochromism.

PANI-Encapsulated Si Nanocomposites with a Chemical Bond Linkage in the Interface Exhibiting Higher Electrochemical Stability as Anode Materials for Lithium-Ion Batteries

A covalent linkage between polyaniline (PANI) and Si nanoparticles in PANI-encapsulated Si nanocomposites was proposed and achieved by a facile and economical synthetic strategy, in which NH2-grafted Si was first obtained via a chemical modification of Si surface and the polymerization of aniline initiated at NH2 group surface was readily accomplished to get PANI shell. The characterizations suggested that NH2 groups were successfully introduced onto Si surface and PANI-encapsulated Si nanocomposites with a core/shell structure were fabricated. Electrochemical tests showed that our proposed Si nanocomposites delivered a high initial specific capacity of 2135[Formula: see text]mAh/g and retained 848[Formula: see text]mAh/g after 100 charge/discharge cycles at a current density of 0.1[Formula: see text]A/g, which were superior than that of the normal PANI-encapsulated Si nanocomposites with the absence of chemical bonds in the interface. The enhanced electrochemical performance was ascribed to the surface chemical modification and the introduction of chemical bond in the interface. NH2 group function of Si could improve the homogeneity of encapsulated PANI shell. Additionally, PANI was tightly anchored to Si nanoparticles via a covalent bond between silicon and PANI, which would greatly inhibit the separation of PANI from Si surface during the expansion/contraction of Si particles. Thus, the structural integrity was maintained. Besides, PANI layer with a unique structure promoted the transport of both electrons and lithium ions.

Graphene beaded carbon nanofibers/ZnO/polyaniline nanocomposites for high performance supercapacitor

Novel unique fabrication of ZnO nanoparticles decorated graphene beaded carbon nanofibers (G-CNF) encapsulated by polyaniline (PANI) nanocomposites through three steps by electrospinning, hydrothermal and in-situ polymerization is reported. As-synthesized G-CNF/ZnO/PANI and CNF/ZnO/PANI nanocomposites were comparatively studied by scanning electron microscopy and electrochemical characterizations for supercapacitor application. Electrochemical measurements of G-CNF/ZnO/PANI electrode revealed the maximum specific capacitance, discharge time, energy density and power density as compared to that of CNF/ZnO/PANI indicating the increase in surface area due to graphene incorporation in electrospinning of carbon nanofibers. The combination of electric double layer charge (EDLC) capacitance from high surface area of G-CNF and pseudo-capacitance from PANI and ZnO nanoparticles facilitates the synergistic effect of ternary components to enhance the electrochemical performance of G-CNF/ZnO/PANI nanocomposite.

Enzymatic Formation of Polyaniline, Polypyrrole, and Polythiophene Nanoparticles with Embedded Glucose Oxidase.

Polyaniline (PANI), polypyrrole (Ppy), and polythiophene (PTh) composite nanoparticles with embedded glucose oxidase (GOx) were formed by enzymatic polymerization of corresponding monomers (aniline, pyrrole, and thiophene). The influence of monomers concentration, the pH of solution, and the ratio of enzyme/substrate on the formation of PANI/GOx, Ppy/GOx, and PTh/GOx composite nanoparticles were spectrophotometrically investigated. The highest formation rate of PANI-, Ppy-, and PTh-based nanoparticles with embedded GOx was observed in the sodium acetate buffer solution, pH 6.0. The increase of optical absorbance at λmax = 440 nm, λmax = 460 nm, and λmax = 450 nm was exploited for the monitoring of PANI/GOx, Ppy/GOx and PTh/GOx formation, respectively. It was determined that the highest polymerization rate of PANI/GOx, Ppy/GOx, and PTh/GOx composite nanoparticles was achieved in solution containing 0.75 mg mL−1 of GOx and 0.05 mol L−1 of glucose. The influence of the enzymatic polymerization duration on the formation of PANI/GOx and Ppy/GOx composite nanoparticles was spectrophotometrically investigated. The most optimal duration for the enzymatic synthesis of PANI/GOx and Ppy/GOx composite nanoparticles was in the range of 48–96 h. It was determined that the diameter of formed PANI/GOx and Ppy/GOx composite nanoparticles depends on the duration of polymerization using dynamic light scattering technique (DLS), and it was in the range of 41–167 nm and 65–122 nm, when polymerization lasted from 16 to 120 h.

Electrochemical behavior of polyaniline nanoparticles suspension: Adsorption and diffusion

A stable suspension of polyaniline nanoparticles (nPANI) in acidic solution can be used in various applications. For the first time, the electrochemical behavior of nPANI as a dispersed phase in phosphoric acid (H3PO4) solution on a gold electrode has been investigated using a series of electrochemical methods including cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy. The prepared suspensions were stable during a long time. The electrochemical results confirmed two redox transformations within the nPANI structure occurred at the potentials of about 0.20 and 0.50 V (vs. Ag|AgCl) which are controlled by the irreversible diffusion and the adsorption mechanism of nPANI particles at the gold surface, respectively. Two main electrochemical parameters including total numbers of redox active sites per nPANI particle (4.2 × 105) and electron-transfer rate constant (9.7 × 10−6 cm s−1) have been determined using CV method. The adsorption process of nPANI particles obeys Langmuir isotherm; additionally, the quantum chemical calculations and Monte Carlo simulation demonstrated that polyaniline macro molecules can replace water and phosphoric acid molecules from the surface upon its adsorption to the gold substrate. The surface analyses of the electrode using Raman spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy confirm the adsorption phenomenon.

The construction of electrochemical aptasensor based on coral-like poly-aniline and Au nano-particles for the sensitive detection of prostate specific antigen

Prostate specific antigen (PSA), as the significant biomarker of prostate cancer, has aroused widespread concern. However, constructing the PSA aptasensor with high sensitivity and low detection limit is still facing huge challenges. In this study, a sensitive electrochemical aptasensor for detecting PSA based on coral-like poly-aniline (PANI)/gold nano-particles (AuNPs) and the peptides was constructed. Coral-like PANI and AuNPs with the diameter of 50–80 nm, as the substrate materials, were directly deposited on glass carbon electrode (GCE) by electrodeposited method. Then, the peptides, as the antifouling materials, were anchored on the modified-electrode, which not only can form antifouling surface to reduce nonspecific adsorption, but also can be as a medium between the modified-electrode and PSA aptamer. Finally, the PSA aptamer was immobilized on the electrode. Based on the synergistic effect of excellent conductivity and special morphology of the substrate materials, and the antifouling ability of peptides, the aptasensor exhibited a high sensitivity of 462.7 μA(ng mL−1)−1 cm−2, wide linear range from 0.1 pg mL-1 to 100 ng mL-1, low limit of detection (LOD) of 0.085 pg mL-1 and good antifouling performance. The aptasensor also possessed outstanding selectivity, reproducibility and stability. Moreover, the aptasensor can directly detect PSA in 10% human serum solutions.

Preparation and Electrochemical Testing of Polyaniline (PANI) Nanoparticles with Uniform Morphology and Good Dispersion in a Water-task-specific Ionic Liquid Medium

Polyaniline (PANI) nanoparticles with uniform morphology and good dispersion were prepared by using the task-specific Ionic Liquid (IL) 1-ester-3-methyl-imidazolium tetrafluoroborate ([EAMIM]BF4) as a soft template by chemical oxidation in a water-IL medium. The morphological, structural and electronic properties of polyaniline (PANI) products, controlled by the IL [EAMIM]BF4, were synthesized and investigated. Products were characterized by SEM, FT-IR and the measurements of conductivity. The addition of [EAMIM]BF4 strongly influenced the morphology, uniformity, and conductivity of the PANI. Depending on the [EAMIM]BF4:ANI ratio, various nanostructures of PANI could be prepared and the dominant morphologies are the rod-like and fiber-like elongated structures under most experimental conditions. Samples prepared in the presence of IL [EAMIM]BF4 show uniform morphology, good dispersion and good electrochemical performance. At the current density of 0.5 A/g, the specific capacitance of PANI was 396 F.g-1. Compared with the PANI without ionic liquids, the specific capacitance was increased by 165 F.g-1. DOI: http://dx.doi.org/10.5755/j01.ms.25.3.19145

Fabrication of Electrically Conductive Cellulose Acetate/Polyaniline/WO3 Nanocomposite Nanofibers with Potential Applications in Electrochemical Devices

In this work, due to the importance of biopolymers utilization in electrochemical applications, a new type of electroconductive/electroactive cellulose acetate (CA) base nanofibers is prepared via electrospinning of acid-doped polyaniline (PANI), WO3 nanopowders and CA. The fabricated nanocomposite mats were evaluated and characterized using various techniques such as scanning electron microscopy (SEM), cyclic voltammetry (CV), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD). SEM images indicated that the nanofibers morphology was ribbon-like, smooth and bead free that may be due to solvent system selection and ambient conditions. Also, the average diameter of CA nanofibers has been decreased from 320 to 230 nm by adding 5 wt % of PANI to CA solution. FTIR results confirmed the existence of hydrogen interaction between the polyaniline and CA molecular chains. The results obtained from XRD and DSC showed that crystalline region of CA/PANI mats has increased by addition of WO3 nanoparticles. Electrochemical analysis showed good electrocatalytic properties for the electrospun CA/PANI/WO3 nanocomposite nanofibers. The results indicated that charge transfer and ohmic serial resistance of the nanocomposites were decreased due to addition of PANI and WO3 nanoparticles.

Nanopolyaniline Coupled with an Anticorrosive Graphene as a 3D Film Electrocatalyst for Efficient Oxidation of Toluene Methyl C-H Bonds and Hydrogen Production at Low Voltage.

A graphene-wrapped polyaniline nanoparticles film embedded in carbon cloth (CC/PANI/G) was fabricated and used as a 3D anodic electrocatalyst for oxidation of toluene methyl C-H groups. The methyl C-H bonds can be oxidized effectively at the CC/PANI/G anode with 99.9 % toluene conversion at a low applied voltage of only 1.0 V, which implies low energy input. Importantly, 86.6 % of toluene methyl C-H groups were converted to benzoyl groups (C=O), and hydrogen was produced efficiently at the cathode. The electrocatalytic efficiency at the CC/PANI/G anode was higher at lower voltage (1.0 V) than at higher voltage (1.5 V), and more hydrogen was produced at the corresponding cathode. The synergistic effect between the dynamic redox chemistry of nanoPANI and the excellent conductivity and anticorrosive action of graphene determined the high electrocatalytic efficiency of the oxidation of toluene methyl C-H groups at the CC/PANI/G anode. Owing to the chemical bonding between graphene and PANI, the anticorrosive CC/PANI/G anodic electrocatalyst was durable and effective for oxidation of toluene methyl C-H groups in acidic environment. This approach provides advanced electrode materials for transforming stable chemical bonds (C-H) into useful functional groups (C=O), which will be beneficial for the synthesis of organic intermediates with coupled hydrogen production.

Probing electrochemical mechanism of polyaniline and CeO2 nanoparticles in alkyd coating with in-situ electrochemical-AFM and IRAS

The corrosion protection and electrochemical mechanism of solvent-borne alkyd composite coating containing 1.0 wt.% polyaniline (PANI) and 1.0 wt.% CeO2 nanoparticles (NPs) for carbon steel in 3.0 wt.% NaCl solution were investigated by means of scanning electron microscopy (SEM), ex-situ, in-situ and electrochemical controlled (EC) atomic force microscopy (AFM), open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) methods. The SEM and ex-situ AFM results revealed the micro- and nanostructure of the composite coating. The in-situ sequential AFM images and line profiling analysis indicated electrochemical activity of the NPs and a high stability of the composite coating in NaCl solution. The results of EC-AFM combined with cyclic voltammetry (CV) demonstrated volume change of the PANI NPs upon reduction and oxidation at certain applied potentials on the coating. The redox reactions between the different forms of PANI and the effect of the CeO2 NPs on the polymerization of the composite polymer were further confirmed by infrared reflection absorption spectroscopy (IRAS). The OCP and EIS results revealed that the composite coating provided an improved corrosion protection for carbon steel within several days of exposure, which was attributed to the barrier protection of CeO2 NPs and the passivation ability of PANI.

Facile Synthesis of the Composites of Polyaniline and TiO₂ Nanoparticles Using Self-Assembly Method and Their Application in Gas Sensing.

The composites of polyaniline and TiO2 nanoparticles with different contents were prepared in the aqueous solution of phosphoric acid, in which the phosphoric acid was selected as the protonic acid to improve the conductivity of polyaniline. In the composites, the TiO2 nanoparticles with the size of about 20 nm were coated by a layer of polyaniline film with a thickness of about 5 nm. Then, the gas sensors were constructed by a liquid–gas interfacial self-assembly method. The gas-sensing properties of the composites-based gas sensors obviously improved after doping with TiO2 nanoparticles, and the sensor response of the composites increased several times to NH3 from 10 ppm to 50 ppm than that of pure polyaniline. Especially when the mass ratio of TiO2 to aniline monomer was 2, it exhibited the best gas response (about 11.2–50 ppm NH3), repeatability and good selectivity to NH3 at room temperature. The p–n junction structure consisting of the polyaniline and TiO2 nanoparticles played an important role in improving gas-sensing properties. This paper will provide a method to improve the gas-sensing properties of polyaniline and optimum doping proportion of TiO2 nanoparticles.