Material Systems for Nano-Scale 3D Printing by Multi-Photon Lithography
Stephen M. Kuebler
Department of Chemistry and CREOL, The College of Optics and Photonics, University of Central Florida
Multi-Photon Lithography is a flexible method for single-step fabrication of 3D structures with feature sizes well below 1 micron. A wide range of material systems has been investigated for multiphoton lithography, including photoresists, chalcogenide glasses, hybrid pre-ceramics, and metals. Post-printing processes have also been developed for transforming polymeric 3D structures into other materials, either by conformal deposition, pyrolysis, structure inversion, or other means. This presentation will give an overview of material systems for multiphoton lithography and show examples of functional 3D nano-scale devices that have been created with these material systems.
Insight on the surface chemistry of bimetallic nanostars: capping agents and stability
Chiara Deriu, MS; Asier Bracho; Alejandro Rizo; Bruce McCord, PhD
Department of Chemistry and Biochemistry, Florida International University, Miami, FL
Anisotropic nanoparticles represent the state-of-the-art substrates for surface-enhanced Raman spectroscopy (SERS), and there is great interest in the development of facile synthetic strategies that achieve these morphologies in a seedless, one-pot, and surfactant-free manner. However, the absence of surfactants as shape directors poses challenges in maintaining the stability of the colloid, and detergents such as CTAB are generally added post-synthesis as stabilizers. This hinders the SERS signal via the formation of a bilayer that prevents a close contact between analyte and metal surface. Ideal capping agents for SERS substrates, on the other hand, should ensure a shelf-life to the colloid without interfering with the SERS measurement. A published protocol for the surfactant-free synthesis of poorly capped bimetallic Au/Ag nanostars was selected as a basis to study alternatives to CTAB as stabilizing agent to be added post-synthesis. DLVO theory of colloid stability was used as a criterion for the selection of candidate stabilizing agents, and UV/Vis spectroscopy was used to evaluate the stability of the colloidal preparations over time. XPS, Zeta potential measurements, and infrared spectroscopy were used to investigate the surface chemistry of the nanostars, and the interaction modes of the candidate stabilizers. Preliminary results obtained from decay studies indicate a pattern of increased capping efficacy for candidate agents bearing carboxylate functions, suggesting that the driving force in the capping process is not purely electrostatic in nature.
Structure predictions of mixed-metal solid state compounds
University of North Florida
Advances in solid-state chemistry benefit from synthesis of new materials and the characterization of their structures and properties. Both exploratory and targeted synthetic methods have unique advantages in the synthesis of new materials. These methods have been used to prepare mixed-metal solid state compounds, which exhibit structural variety and diverse physical properties. Structure prediction software based on the bond valence approach has been developed to predict the structure of a range of phase compositions. Developments include structure stability predictions and temperature dependent calculations, enabling the examination of structural phase transitions and the associated changes in unit cells, atomic positions, bond distances, bond angles, etc. Representative mixed metal solid state systems are examined in the context of the predicted and experimental structures.
Synthesis and Characterization of Lead Halide Perovskites for Solid State Lighting
Edward T. Nguyen
Florida State University
Down-shifting phosphors are routinely used in solid state lighting to convert higher energy UV or blue light to visible light. However, color quality of commercial LEDs are modest and new RGB phosphors are needed to tune the color of light. Commercial LEDs are composed of bulk semiconductors that typically contain materials on the DOE high risk index. For improving performance of down-shifting phosphors, size of the phosphor must be reduced to sub 10nm to reduce scattering of the pump led, the host lattice must minimize the amount of rare earth metals used, and must absorb pump LED irradiation and convert to pure red, green, and blue emission for optimal color quality. Here we present the synthesis of lanthanide-doped lead-halide perovskites (CsPbX3; X = Cl, Br, I). Lanthanide emission is accomplished by energy transfer from surface ligands to lanthanide metal centers by using the molecular antenna effect. Optical measurements of the nano-perovskites will be discussed including absorption, emission, lifetime, and quantum yields. Ligand exchanges were completed in efforts to improve quantum efficiencies and the nanoperovskites were characterized by pXRD, TEM, EPR, and FT-IR.
Experimentally Correlating the Spatial Distribution of Fluorine to the Growth of Anatase TiO2 Crystal Facets
Justin R. Mulcahy, Shuai He, Decarle S. Jin, Wenxiao Guo, Sarah Arteta, Esdras Lopez, Zihua Zhu, and Wei David Wei
Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
Although the capability of fluorine to selectively stabilize anatase titanium dioxide (TiO2) crystal facets has been recognized, resolving its physical distribution remains empirically elusive. Here, we provide direct experimental evidence to reveal the spatial location of fluorine on the surface of anatase TiO2 truncated bipyramid (TB) single crystals using nanoscale secondary ion mass spectrometry (NanoSIMS). Fluorine was found to preferentially adsorb on the (001) facet over the (101) facet of TBs. Moreover, NanoSIMS depth profiling exhibited a significantly different fluorine distribution between these two facets in the near-surface region, which correlates the essential role of lattice fluorine doping with the anisotropic crystal growth of TBs.
Expanding Cu-ligated multilayers for use in hybrid lithographic strategies
Alexandra M. Patron1, Daniel F. Santavicca2, Corey P. Causey1, Thomas J. Mullen1
1 - University of North Florida, Department of Chemistry
2 - University of North Florida, Department of Physics
The development of hybrid-lithographic strategies to fabricate nanoscale features with tailored chemical functionalities has garnered tremendous interest in recent years for applications such as nanoelectronic and sensor fabrication. The molecular-ruler process shows great utility for this purpose as it combines top-down lithography for the creation of complex architectures over large areas in conjunction with molecular self-assembly, which enables precise control over the physical and chemical properties of small local features to employed to produce registered nanogaps between metal features. The solution deposition of mercaptoalkanoic acids and metal ions are commonly used to generate the metal-ligated multilayers employed in the molecular-ruler process; however, few studies have explored molecules with varied chemical functionalities. Here, we explore the solution and vapor deposition of alkanethiol molecules as the terminating layer of metal-ligated SAMs. We observe that the solution deposition of alkanethiol molecules resulted in islands of low surface coverages with features that varied in height. Unlike solution deposition, islands produced via vapor deposition exhibit markedly higher surface coverages of uniform heights. To illustrate the applicability of the vapor deposition approach, metal-ligated multilayers, both with and without a vapor-deposited alkanethiol layer as the terminating layer, are utilized to create nanogaps between Au features using the molecular ruler process. Expansion of the molecular-ruler process to include molecules with other chemical functionalities and tailored deposition conditions has the potential to improve the overall versatility, and thus the utility, of this process.