Colorimetric nanofibers as optical sensors

Sensors play a major role in many applications today, ranging from biomedicine to safety equipment, where they detect and warn us about changes in the environment. Nanofibers, characterized by high porosity, flexibility, and a large specific surface area, are the ideal material for ultrasensitive, fastresponding, and user-friendly sensor design. Indeed, a large specific surface area increases the sensitivity and response time of the sensor as the contact area with the analyte is enlarged. Thanks to the flexibility of membranes, nanofibrous sensors cannot only be applied in high-end analyte detection, but also in personal, daily use. Many different nanofibrous sensors have already been designed; albeit, the most straightforward and easiest-to-interpret sensor response is a visual change in color, which is of particular interest in the case of warning signals. Recently, many researchers have focused on the design of so-called colorimetric nanofibers, which typically involve the incorporation of a colorimetric functionality into the nanofibrous matrix. Many different strategies have been used and explored for colorimetric nanofibrous sensor design, which are outlined in this feature article. The many examples and applications demonstrate the value of colorimetric nanofibers for advanced optical sensor design, and could provide directions for future research in this area

Strength development of recycled concrete aggregate stabilized with fly ash-rice husk ash based geopolymer as pavement base material

This research studies on the usage of fly ash (FA) and rice husk ash (RHA) based geopolymers for improving the compressive strength of recycled concrete aggregate (RCA) to be a lightweight stabilised pavement base material. A mixture of FA from coal-burning power plants and RHA from rice milling process was used as a precursor while the liquid alkaline activator (L) was a mixture of sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3). Various RHA/FA ratios between 100/0 and 0/100 and NaOH/Na2SiO3 ratios between 50/50 and 100/0 were used in this study. The FA-RHA-geopolymer stabilised RCA samples, at each NaOH/Na2SiO3 ratio were prepared at the optimum liquid alkaline activator content (OLC) for unconfined compressive strength (UCS) tests. The UCS tests were conducted after 7, 28 and 60 days of curing. The test results indicate that the UCS of FA-RHA-geopolymer stabilised RCA increases as the RHA/FA and NaOH/Na2SiO3 ratios decrease and the curing time increases. Based on the Department of Highways, Thailand, the 60/40 RHA/FA and 60/40 NaOH/Na2SiO3 mix proportions are recommended for both low and high traffic volume roads with a low unit weight of 21.1kN/m3. This research study confirms the potential of FA-RHA-geopolymer stabilised RCA as an alternative stabilised road base material