Supercapacitors have attracted considerable attentions due to their high energy and power densities as well as long cycle life. Recently, our lab developed a facile technique that allows the fabrication of highly ordered nanopillar structures. Nanostructured electrodes prepared for supercapacitors using this technique show considerable capacitance enhancement. The simplicity of the fabrication method together with superior power density and energy density make this device very attractive for the next generation energy storage systems.
Nanostructures using SNAP technique
We developed an unconventional fabrication technique called spin-on nanoprinting (SNAP) to generate sub-100 nm structures. The dimensions of printed nanostructures are almost the same as that of the mold. The printed patterns can be used as a replica for printing second-generation structures using other polymeric materials. SNAP is an inexpensive process and requires no special equipment for operation.
We developed a facile method for creating tailored one-dimensional nanostructured silver, tin or zinc substituted indium oxide electrode structures over a large area. Using this technique, it is possible to produce high aspect ratio nanoscale structures with feature sizes below 100nm. We show that the optical and electronic properties of these electrodes are closely correlated to the nanostructure dimensions and can be very easily tuned by changing feature size. Nanostructure dependent work function highlights the quasi-plasmonic nature of the electrodes. Optimization of the nanostructured electrode transparency and conductivity for a specific photovoltaic system is expected to provide improvement in device performance.
For details: "Fabrication, Electrical and Optical Properties of Silver, Indium Tin Oxide (ITO) and Indium Zinc Oxide (IZO) Nanostructure Arrays" (Cover story), Phys. Status Solidi A, 1–8 (2013).
Lasers are currently indispensable for many applications in a variety of fields. This includes military, telecommunications, manufacturing and medicine. Although lasers are a very powerful source of energy, at times, they can be damaging. Laser systems are so powerful that industries often utilize high power laser systems for cutting and drilling. For humans, unintended laser irradiations can damage eyes or other body parts. This poses high health threat to those who are working with such laser systems. In military applications, lasers are incorporated in many types of weaponry. These lasers can damage sensors or blind military personals. Therefore, there is a considerable need for a device to protect people and optoelectronic devices from laser threats. We are developing and testing materials which can diffuse high intensity laser lights while allowing low intensity laser lights to pass through it.
Details are given in:
- SPIE Newsroom report
- "Evolution of Nonlinear Optical Properties: From Gold Atomic Clusters to Plasmonic Nanocrystals", Nano Letters, 12, 4661−4667 (2012)
- "Optical power limiting in fluorinated graphene oxide: An insight into the nonlinear optical properties", J. Phys. Chem. C, 116, 25955 (2012)
- "Enhanced optical limiting in nanosized mixed zinc ferrites", Appl. Phys. Lett. 100, 221108 (2012)
We have developed a measurement technique, by combining Optical Z-scan and Photoacoustic Z-scan, called OPAZ-scan. This technique benefits from the advantages of both measurements. With this system nonlinear absorption of both optically light and dark sample can be measured. Furthermore, it is also found that the simultaneous measurement of the optical and photoacoustic signals gives enhanced insight into optical nonlinearity, especially ones with mixed nonlinear scattering and absorption.
For details: "Simultaneous optical and photoacoustic measurement of nonlinear absorption", Appl. Phys. Lett. 102, 041116 (2013).
Highly Sensitive Photorefractive Polymers
Photorefractive composites derived from conducting polymers offer the advantage of dynamically recording holograms without the need for processing of any kind. Thus, they are the material of choice for many cutting edge applications, such as updatable 3D displays and imaging through a scattering medium. Photorefractive polymers sensitive to visible light have evolved to a state of high performance and reliability. Organic polymer materials also have the inherent advantages of ready manipulation of component formulations to suit a given application and low cost. Unlike many other permanent recording materials such as photopolymers, holograms can be written and erased in PR materials many times without the need of chemical processing. Our current focus is the development of highly sensitive polymers for video-rate holographic 3D display applications. Our group is developing photorefractive polymers using highly efficient new sensitizers.
For details: "Photoconducting polymers for photorefractive 3D display applications" (invited review article) Chem. Mater. 23, 416 (2011)