This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 10(6) was synthesized using low-temperature free-radical polymerization. The PSS was used as both a doping agent and a binding agent for the polymerization of aniline monomers in a biphasic system (water-chloroform) at -50 °C. The high Mw of PSS resulted in relatively large particle sizes and smooth surfaces of the PSS-doped PANI. These physical characteristics, in turn, resulted in low interparticle resistance and high conductivity. In addition, the PSS allowed homogeneous dispersion of reduced graphene sheets through electrostatic repulsion. The prepared PSS-doped PANI/graphene solutions showed good compatibility with flexible poly(ethylene terephthalate) (PET) substrates, making them suitable for flexible sensor electrodes. Changes in the charge-transport properties, such as protonation level, conjugation length, crystalline structure, and charge-transfer resistance, of the electrode materials were the main factors influencing the electrical and sensor performance of the PSS-doped PANI-based electrodes. PSS-doped PANI/graphene composites containing 30 wt% graphene showed the highest conductivity (168.4 S cm(-1)) and the lowest minimum detection level (MDL) for H2S gas (1 ppm). This result is consistent with the observed improvements in charge transport in the electrode materials via strong π-π stacking interactions between the PANI and the graphene sheets.

Due to rapid advances in technology which have contributed to the development of portable equipment, highly sensitive and selective sensor technology is in demand. In particular, many approaches to the modification of wireless sensor systems have been studied. Wireless systems have many advantages, including unobtrusive installation, high nodal densities, low cost, and potential commercial applications. In this study, we fabricated radio frequency identification (RFID)-based wireless sensor systems using carboxyl group functionalized polypyrrole (C-PPy) nanoparticles (NPs). The C-PPy NPs were synthesized via chemical oxidation copolymerization, and then their electrical and chemical properties were characterized by a variety of methods. The sensor system was composed of an RFID reader antenna and a sensor tag made from a commercially available ultrahigh frequency RFID tag coated with C-PPy NPs. The C-PPy NPs were covalently bonded to the tag to form a passive sensor. This type of sensor can be produced at a very low cost and exhibits ultrahigh sensitivity to ammonia, detecting concentrations as low as 0.1 ppm. These sensors operated wirelessly and maintained their sensing performance as they were deformed by bending and twisting. Due to their flexibility, these sensors may be used in wearable technologies for sensing gases.

Dopamine (DA), as one of catecholamine family of neurotransmitters, is crucially important in humans owing to various critical effects on biometric system such as brine circuitry, neuronal plasticity, organization of stress responses, and control of cardiovascular and renal organizations. Abnormal level of dopamine in the central nervous system causes several neurological diseases, e.g., schizophrenia, Parkinson's disease, and attention deficit hybperactivity disorder (ADHD)/attention deficit disorder (ADD). In this report, we suggest the fabrication of nonenzyme field effect transistor (FET) sensor composed of immobilized Pt particle decorated conducting-polymer (3-carboxylate polypyrrole) nanoparticles (Pt_CPPy) to detect dopamine. The hybrid nanoparticles (NPs) are produced by means of facile chemical reduction of pristine CPPyNP-contained Pt precursor (PtCl4 ) solution. The Pt_CPPys are then immobilized on an amine-functionalized (-NH2 ) interdigitated-array electrode substrate, through the formation of covalent bonds with amine groups (-CONH). The resulting Pt_CPPy-based FET sensors exhibit high sensitivity and selectivity toward DA at unprecedentedly low concentrations (100 × 10(-15) m) and among interfering biomolecules, respectively. Additionally, due to the covalent bonding involved in the immobilization process, a longer lifetime is expected for the FET sensor.

Hydrogen (H 2 ) gas is used extensively in many industrial processes and is an essential fuel source in clean-energy transportations and power generation applications 1,2 . However, it is highly flammable and explosive at volume concentrations higher than ca. 4%. Therefore, hydrogen sensors that have high sensitivity, rapid response, and reversibility are required to detect and/or monitor minute hydrogen leakages in industrial applications 3,4 . In general, commercial hydrogen sensors composed of metal oxide (SnO 2 ) films meet these demand but require an operating temperature of over 200 °C, which increases the overall power consumption of the sensing device [5][6][7] . Palladium (Pd) is an attractive candidate to replace metal oxides, because H 2 molecules are selectively adsorbed onto the surface of Pd by dissociation into hydrogen atoms (H 2 → 2H), and diffused into the interstitial sites of Pd structure. As a result, the phase of Pd transfer a solid solution of Pd/H (α -phase) and a palladium hydride (β -phase), resulted in resistance changes at room temperature. However, materials based on Pd is susceptible to structural changes (such as vacancy and dislocation), which are increased during the phase transition of Pd (α to β ) that occurs at hydrogen concentration higher than 2%, causing have been known to collapse during the sensing reaction due to an irreversible phase change [8][9][10][11][12][13][14] . The shape control of metal nanostructure is important factor to enhance the activity and stability 15 . Numerous research have studied to improve the performance by change the nano-sized morphology such as nanocube 16 . Furthermore, the substrate for the introduction of these shape is also play a critical roles due to the improvement of the charge transport and stability of active materials.

The conducting nanocomposite paste composed of multidimensional hollow nanoparticles and PANI:PSS easily forms sensing area in the wireless sensor tag.