IIT-Jodhpur has developed a ‘cold-plasma detergent in environment’ (CODE) device under an industry-sponsored project to reduce the risk of infection from airborne pathogens indoors, by using DBD plasma in combination with nanotechnology.

The device relies on a cold plasma discharge for the generation of plasma detergent ions. It has a geometry plasma source with specially designed electrodes and a filter coated with metal oxide nanoparticle catalysts. It is environment-friendly and uses low-cost electrode materials. The need for feed gas, pallets and/or differential pressure has been eliminated by virtue of a new design and process. It is well known that the highest negative ion concentration is in natural clean air; high negative ion concentration dramatically improves indoor air quality and health.

The CODE device is able to generate efficient plasma detergent ions with a larger sustenance time, at atmospheric pressure (without additional gas or vacuum system). This new type of discharge plasma generation requires low average power and can produce plasma detergent ions in lakhs, with an average ion sustenance time of more than 25 seconds. The device is easily scalable and free from UV-light and ozone.

What can it do?

The device has been tested for disinfection of total microbial counts, reduction of total fungal counts, dust and pollens in indoor environments bigger than 1,728 crore cubic cm and showed that pristine natural environment is quite realisable from the CODE device, says a press release from IIT-Jodhpur.

Nanoscale photodetector

Researchers at IIT-Madras have developed an alternative to the silicon photodetector, which is a major component in modern appliances. A nanoscale photodetector developed by IIT-Madras has higher energy efficiency compared to existing materials.

A photodetector or photosensor converts light radiation into an electrical signal, which results in excess charge carriers. They are used in applications ranging from high-tech night vision equipment, camera, optical spectroscopy systems and optical communications to everyday appliances such as automatic door opening systems, barcode readers and intelligent lighting systems.

Prof Somnath C Roy, Department of Physics, who led the research, says they have “demonstrated a device made from a common oxide material that is highly stable and versatile and achieves excellent response to a wide-spectrum of light because of unique core-shell nanostructure-based design”.

The geometry of nanowires makes them efficient for light detection. Nanowires are crystalline wires whose diameter is one-thousandth that of human hair.

The higher surface-to-volume ratio and short channel length of the nanowire devices make them more photo-sensitive than the larger bulk photodetectors made from the same materials. Different kinds of nanowires detect different types of light sources; the detector developed at IIT-Madras can identify ultraviolet (harmful to human tissue) and visible light.

The device was fabricated via single-step photolithography comprising a cupric oxide and cuprous oxide core-shell architecture — that is, cupric oxide nanowire as the inner core and the cuprous oxide nanoparticles layer as the outer shell.

The electrical contacts are taken from the outer cuprous oxide shell. When light falls on this single nanowire device, charges are generated in both the inner core and outer shell; however, due to the specific alignment of the energy bands, charges relevant to the photodetection process migrate towards the outer shell.

The performance of the device is comparable with the reported silicon- or germanium-based photodetectors. Efforts are underway to explore nanowire transistor for single-photon detection and high-speed applications in nanophononics.

Green synthesis of medicinal compound

E Poonguzhali of the Department of Chemistry, IIT-Madras has been granted a patent for developing a green method of producing a medicinally important compound called Benzo[b]thiophene.

The compound is present in a range of medicines such as raloxifene (used in osteoporosis), zileuton (asthma), and sertaconazole (antifungal medication) and the one-step synthesis of the two-substituted benzo[b]thiophene can replace hazardous industrial production.

Current methods of production need high temperatures, emit sulphureous gases. Poonguzhali’s method involves using a water medium, room temperature, odourless xanthate, open-air atmosphere, and inexpensive starting materials and catalysts.