Research Interests

Research efforts in Arachchige group are focused on the synthesis, characterization, and assembly of novel inorganic nanomaterials with unique and tunable physical properties; fundamental investigation of how the structure, morphology, composition, and physical properties are related; in order to advanced technologies such as chemical sensing, cellular imaging, energy conversion, and heterogeneous catalysis. The synthesis of nanoscale materials with unique physical properties and their self-assembly into functional nanostructures is a critical field of endeavor today. However, precise control over nanomaterials properties and their interactions in nanostructured assemblies has proven a challenging task that hinder widespread application of nano-science/technology. In response to these critical needs, a highly interdisciplinary program is developed, spanning chemistry, physics, engineering, and medicine, working towards the overarching goal of enabling “novel efficient materials” for advanced technological applications. There are three main thrusts of the research.

(1) Direct-Gap Si1-xSnx and Ge1-xSnx Nanocrystals for High-Efficiency Optoelectronics

Low-cost, non-toxic and abundantly-produced, Group IV semiconductors are the ideal active components for a broad range of devices. However, Si and Ge are of limited use in optoelectronics (solar cells, light emitting diodes, sensing, and imaging) because of their indirect energy-gaps, which make their interactions with light much less efficient than many other semiconductors. We propose to develop nanocrystalline Group IV semiconductors with direct energy-gaps that will greatly enhance the efficiency of Si and Ge optoelectronics. This will be accomplished through concerted influences of quantum confinement and alloying with Sn, and will result in SixSn1-X and GexSn1-x alloy nanocrystals (NCs) with significant potential in visible to near-infrared optoelectronics. This research addresses the major bottleneck (indirect energy-gaps) for efficient use of Si and Ge in optoelectronics and establishes a strikingly new technology that combines the unique advantages of nanoscale device design and fabrication with attractive technological features of low-cost, non-toxic Group IV semiconductors potentially impacting the future design of high-efficiency optoelectronics.

(2) Direct Self-Supported Assembly of Metal and Semiconductor Nanoparticles into Porous Nanostructures for Surface Enhanced Raman Scattering (SERS) and Heterogeneous Catalysis

Nanomaterials often exhibit unique properties that hold enormous potential in breakthrough technologies. However, advances in nanotechnology are predicated on our ability to create, manipulate, and organize nanoscale materials into functional superstructures with useful and controllable physical properties. To address this issue, Arachchige group is developing innovative strategies for direct hardwiring of metal and semiconductor NCs into high-surface-area, highly-conductive, hierarchically-porous nanostructures (aerogels), with no use of intervening ligands and substrate supports. The resultant aerogels are expected to exhibit optical transparency or opacity, high surface area and hierarchical porosity, and superior electrical transport properties, making them promising for application in a number of new (chemical sensing and electrocatalysis) technologies.

This work builds fundamental understanding of the integration of chemically similar/dissimilar systems into macroscopic nanostructures, and of the emerging optical/electronic properties and chemical functionalities. It also enables traditional sol-gel chemistry to emerge as a versatile route for NC self-assembly and offers new perspectives to build confined nanostructures as self-supported monoliths or nanostructured thin films. These efforts will result in a truly new class of high-surface-area, highly-conductive, hierarchically-porous metal and semiconductor nanostructures that exhibit maximum surface area per unit mass for efficient and sustainable application in future technologies.

(3) Nanostructured Transition Metal Phosphides for Photocatalysis and  Electrocatalysis

Transition metal phosphides (TMPs) are a class of materials that have been historically important across many societally relevant applications, and remain at the forefront of modern science and technology, specifically as nanostructured materials. Vast majority of TMPs exhibit a range of physical properties of both fundamental and technological interest depending on their chemical identity and crystal phase. Underpinning their application is the ability to synthesize TMPs with precisely controlled features –including crystal structure, morphology, and composition– that directly impact their physical properties and chemical reactivity. Arachchige group is developing novel and efficient wet-chemical syntheses for size, shape, and phase controlled nanostructured TMPs (Zn3P2, Ni2-xMoxP, Co2-xMoxP, Ni2-xWxP and Co2-xMoxP) that exhibit tremendous potential in photo-/electro-chemical water splitting, alcohol oxidation and oxygen reduction fuel cell reactions. This research will build new knowledge, capabilities, and high-efficiency nanostructured metal phosphides of broad importance to chemists, physicists, and engineers while impacting diverse applications in photocatalysis and electrocatalysis.