Search

Hydroxyapatite/poly(methyl methacrylate) (HA-PMMA) nanocomposites are extensively used in biomedical fields. Therefore, the design and development of low-cost and industrially viable novel methods are essential to synthesize HA-PMMA nanoparticles. In this letter, we report such an economical, simple and industrially applicable novel method to synthesize nanosized HA-PMMA composite particles using extensively distributed dolomite.

Humidity sensors have been developed based on a wide variety of materials such as ceramic, semiconductors and polymers. However, slow recovery rates is one of the major ongoing concerns of flexible poly(vinyl alcohol) (PVA) based humidity sensors. In this study, a simple, cost effective, fast responding, fast recovering and high sensitive, resistive poly(vinyl alcohol) (PVA) based humidity sensor was developed through the development of controlled conjugation system in PVA polymer matrix by hydroiodic acid (HI) treatment. Changes in structural and morphological parameters on sensor performance were investigated. Resistance of the sensor increased from 10.2 kΩ to 4.5 MΩ when relative humidity (RH) decreased from 92% to 7% RH, while capacitance varied slightly from 70 nF to 100 nF. The response and recovery times of the sensor were measured to be 224.6 s and 56.3 s respectively at room temperature when switching between 50% and 90% RH, demonstrating excellent performance towards fluctuating humidity levels. The results indicate the sensor is capable of measuring humidity levels above 30% with full scale recovery by only consuming 25% of the sensing time. Cost-effective, flexible, fast recovery and resistive sensing can be recognized as the most effective potential applications for this sensor.

Palladium nanoparticles display fascinating electronic, optical and catalytic properties, thus they can be used for various applications such as sensor fabrication. Conducting polymers such as polyaniline have also been widely used in sensor technology due to its cost effectiveness, versatility, and ease of synthesis. In this research, attention was given to unify the exceptional properties of these two materials and construct palladium nanoparticle coated polyaniline films to detect hydrogen and moisture. Electrochemical polymerization of aniline was carried out on gold sputtered epoxy resin boards. Polyaniline film was generated across a gap of 0.2 mm created by a scratch made on the gold coating prior to electrochemical polymerization. A palladium nanoparticle dispersion was prepared using sonochemical reduction method and coated on to polyaniline film using drop-drying technique. Polyaniline only films were also fabricated for comparative analysis. Sensitivity of films towards humidity and hydrogen was evaluated using impedance spectroscopy in the presence of the respective species. According to the results, polyaniline films exhibited an impedance drop in the presence of humidity and the response was significantly improved once palladium nanoparticles were incorporated. Interestingly, polyaniline only films did not respond to hydrogen. Nevertheless, palladium nanoparticle coated polyaniline films exhibited remarkable response towards hydrogen.