Hydrochromic and Photoluminescent materials are attractive for applications in optical memory devices and security inks in banks and government agencies. Static luminescent responses are easy to duplicate and act as loopholes in dissemination of confidential information. Stimuli-responsive photoluminescent materials, therefore, have the potential to overcome these limitations. Further, such materials being integrated into a rewritable paper, would eliminate the difficulty associated with their integration into digital media devices.
We develop new organic molecule designs for using water as an ink. Organic dyes can be coated on the surface of a paper and upon contact with water the dye molecules are arranged in a slip-stacked manner eventually changing the optical properties. This slip-stacked arrangement is assisted by the hydrogen bonds between dye and solvent molecules.
The hydrochromic property has a wide applicability both at organizational levels and for personal use. Considering the potential commercial benefits, we develop designs for different applications like self-expiring security printing and anti-counterfeiting currency notes.
Inkjet-printable hydrochromic paper for encrypting information and anticounterfeiting
Self‐assembly is a process in which molecules are spontaneously organized into an aggregate with a well‐defined structure. Nanomaterials of different dimensions can be synthesized by molecular self-assembly. Proper molecular design allows for long‐range ordering of π‐conjugated molecules. Our self‐assembly approach in synthesizing nanofibers for applications like air-filtration is inspired by Lego-bricks where pieces of Lego are put together into a large assembly.
We develop different kinds of engineered organic molecules for nanofiber self-assembly. The organic molecules synthesized are hydrophobic in nature and tend to stack up in the solution as they come closer to form interesting shapes of nanoparticles and eventually nanofibers.
An important aspect of these nanofibers to work as an air filter is their ability to self-fixate with the non-woven nylon mesh which is a commonly used microfibered material. Air-filters are generally gauged by a parameter called quality factor that depends further on two factors namely particle filtration efficiency and air permeability. While in most commercial respirators, the air permeability is quite low though the filtration efficiency is high, leading to a low quality factor. Our nanofibrous air filter has pores of nano-dimensions which aids in filtering the harmful PM2.5 particles with an efficiency comparable to the commercial filter at the same time without affecting the air flow and breathability which is crucial for air filters.
Nanofibrous Mesh Self‐Assembled from Molecular LEGOs for High Efficiency Air Filtration
Engineered organic molecules play a vital role in photovoltaic technologies like organic solar cells and dye-sensitized solar cells. Considering the various problems associated with the use of liquid electrolytes such as leakage, dye desorption and corrosion of the electrodes, many attempts are being been made to improve the stability, mobility of holes and performance of the device by replacing liquid redox couples either with solid-state electrolytes such as organic hole transport materials and organic ionic conductors.
We design and synthesize solid-state energy transfer redox couples that have dual characteristics i.e. work as a redox mediator as well as light harnesser to improve photovoltaic efficiency.
Non-radiative energy transfer with organic ionic redox couples
