The use of polycarbonates as thermally decomposable, sacrificial materials for the formation of microchannels is presented. Polycarbonates decompose in the temperature range of 200-300 • C. Two polycarbonates, polyethylene carbonate and polypropylene carbonate, have been used to fabricate microchannels in three different types of encapsulants: an inorganic glass (silicon dioxide), a thermoplastic polymer (Avatrel dielectric polymer) and a thermoset polymer (bisbenzoycyclobutene Cyclotene 3022-57). This paper presents the details of the fabrication process, a thermogravimetric analysis of the sacrificial materials, and the kinetic parameters for the decomposition process. The presence of oxygen or water was found to impact on the decomposition of the sacrificial material. This paper demonstrates the feasibility of forming buried air-cavities in a variety of encapsulants at a modest temperature, thus enabling the use of a wide range of dielectric materials with different thermal stabilities and properties.

Development of facile routes to the fabrication of thin film substrates with tunable surface enhanced Raman scattering (SERS) efficiency and identification of the optimal conditions for maximizing the enhancement factor (EF) are significant in terms of both fundamental and application aspects of SERS. In the present work, polymer thin films with embedded bimetallic nanoparticles of Ag-Au are fabricated by a simple two-stage protocol. Ag nanoparticles are formed in the first stage, by the in situ reduction of silver nitrate by the poly(vinyl alcohol) (PVA) film through mild thermal annealing, without any additional reducing agent. In the second stage, aqueous solutions of chloroauric acid spread on the Ag-PVA thin film under ambient conditions, lead to the galvanic displacement of Ag by Au in situ inside the film, and the formation of Ag-Au particles. Evolution of the morphology of the bimetallic nanoparticles into hollow cage structures and the distribution of Au on the nanoparticles are revealed through electron microscopy and energy dispersive X-ray spectroscopy. The localized surface plasmon resonance (LSPR) extinction of the nanocomposite thin film evolves with the Ag-Au composition; theoretical simulation of the extinction spectra provides insight into the observed trends. The Ag-Au-PVA thin films are found to be efficient substrates for SERS. The EF follows the variation of the LSPR extinction vis-à-vis the excitation laser wavelength, but with an offset, and the maximum SERS effect is obtained at very low Au content; experiments with Rhodamine 6G showed EFs on the order of 10(8) and a limit of detection of 0.6 pmol. The present study describes a facile and simple fabrication of a nanocomposite thin film that can be conveniently deployed in SERS investigations, and the utility of the bimetallic system to tune and maximize the EF.

Highly sensitive and stretchable PDA–PAA–Cr3+ hydrogel capacitive strain sensor is fabricated and used to monitor mechanical deformation and human motion.

Polydiacetylenes are a class of conjugated polymers exhibiting unique color and fluorescence properties and employed as useful sensing vehicles. Here we demonstrate for the first time that the dielectric properties of polydiacetylenes can be exploited for vapor sensing. Specifically, electrodes coated with polydiacetylenes, embedded within a porous polyvinylpyrrolidone (PVP) matrix, exhibit significant capacitance transformations upon exposure to different vapors. The capacitive response of the polydiacetylene/PVP films depended upon both the structures of the diacetylene monomer and the extent of ultraviolet irradiation (i.e., polymerization), underscoring a unique sensing mechanism affected by conjugation, structure, and dielectric properties of the polydiacetylene/polymer matrix. Importantly, the variability of polydiacetylene structures allows vapor identification through an array-based pattern recognition (i.e., artificial nose). This study opens new avenues for applications of polydiacetylene systems, particularly pointing to their dielectric properties as powerful sensing determinants.

Hollow bimetallic nanoparticles of silver-palladium (Ag-Pd) are generated in situ inside poly(vinyl alcohol) (PVA) thin films by a two-stage process. In the first stage, Ag-PVA is fabricated by mild thermal treatment of a spin-coated thin film, with the polymer functioning as the reducing agent for the embedded metal precursor ions as well as the stabilizer for the generated nanoparticles. In the second stage, an aqueous solution of potassium palladium chloride (K 2 PdCl 4 ) is spread on this film under ambient conditions, whereupon Pd gets deposited on the Ag nanoparticles through a Galvanic displacement reaction and alloys with it. A crucial requirement of relatively large Ag nanoparticles that can act as the sacrificial template in the second stage is met by the addition of catalytic amounts of cupric ions in the first stage.A gradual variation of the concentration of K 2 PdCl 4 solution used in the in situ process allowed a systematic demonstration of the evolution of the bimetallic nanoparticles with the eventual formation of hollow particles with Ag-Pd alloy walls. The high catalytic efficiency of the Ag-Pd hollow nanoparticle-embedded PVA thin film is demonstrated by its application in the Suzuki-Miyaura reaction.