Alfredo A. Martinez-Morales

Size Control of Gold Nanoparticles Grown on Polyaniline Nanofibers for Bistable Memory Devices

Controlling reaction temperature for a set time enables the size of gold nanoparticles autoreduced on the surface of polyaniline nanofibers to be controlled. The size of the gold nanoparticles can be used to tune the electrical bistable memory effect in gold/polyaniline nanofiber composite devices. Turn-on voltages and on/off ratios improve with decreasing nanoparticle size, making this a promising method to enhance performance and create smaller devices. Long-term stability of the composites can be improved by the addition of stabilizers following autoreduction of the gold nanoparticles.

Nanoscale memory characterization of virus-templated semiconducting quantum dots.

We have developed a substrate-based bottom-up approach to assemble two different color emitting quantum dots (CdSe/ZnS core/shell QDs) on the surface of a novel virus mutant, CPMV-T184C. Electrical characteristics of individual hybrids were investigated by conductive atomic force microscopy for potential digital memory applications (i.e., RAM). These individual 40 nm CPMV-QD(1,2) hybrids exhibited reversible bistable electrical behavior during repeatable writing-reading-erasing processes at the nanoscale.

Periodic alignment of Si quantum dots on hafnium oxide coated single wall carbon nanotubes

We demonstrate a bottom up approach for the aligned epitaxial growth of Si quantum dots (QDs) on one-dimensional (1D) hafnium oxide (HfO2) ridges created by the growth of HfO2 thin film on single wall carbon nanotubes. This growth process creates a high strain 1D ridge on the HfO2 film, which favors the formation of Si seeds over the surrounding flat HfO2 area. Periodic alignment of Si QDs on the 1D HfO2 ridge was observed, which can be controlled by varying different growth conditions, such as growth temperature, growth time, and disilane flow rate.

Soiling measurement station to evaluate anti-soiling properties of PV module coatings

Soiling can be a significant loss factor for PV systems, accounting for >5% annual energy loss in locations without frequent rainfall. Therefore, many manufacturers are investigating the potential benefits of incorporating anti-soiling or self-cleaning properties into PV module coatings. In order to study the potential anti-soiling behavior of various surface treatments, we have deployed a test station with custom-made PV modules having coatings with both hydrophilic and hydrophobic properties that may inhibit soiling and/or induce self-cleaning. The soiling of each sample is determined by comparison to an automatically washed reference cell in the station. We present the motivations for and design of the station, along with preliminary results regarding the impact of the coatings on soiling.

Effects of ionic liquid to water ratio as a composite medium for the synthesis of LiFePO4 for battery

LiFePO4 is a highly researched cathode material that serves as an alternative material for traditional commercial lithiumion batteries such as LiCoO2. Currently, there are a number of different methods to synthesize LiFePO4 including: hydrothermal, solid state, spray pyrolysis, and coprecipitation. Our proposed method has the potential to provide an ecologically friendly and economically competitive way to synthesize LiFePO4 by utilizing ionic liquid and water, as a composite synthesis medium. The addition of water to ionic liquid can be beneficial as it can act as a mineralizer to bring insoluble precursors to form LiFePO4 seed crystals. Furthermore, this method provides the possibility of recycling the ionic liquid for repeated synthesis processes. In this work, we study the effects of ionic liquid to water ratio on the crystallinity and morphology of the synthesized material. Our group was able to conclude a reaction medium utilizing a ratio of equal parts of 1-ethyl-3-methyl imidazolium trifluoromethane sulfonate (EMIM Otf) and water, or a slightly favored ionic liquid ratio, increases the efficacy of the synthesis route. Crystallinity and purity was determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) was used to determine morphology and crystal sizes, and energy dispersion spectroscopy (EDX) was used for elemental analysis.

A comparison between two MPC algorithms for demand charge reduction in a real-world microgrid system

This paper describes an evaluation between two model predictive control (MPC) algorithms for microgrid energy management combined with solar production and battery energy storage for demand charge reduction in a real-world microgrid system. The first control algorithm is a constant threshold MPC (CT-MPC) that works well on a system with relatively stable solar generation and a well-known building load profile. CT-MPC can maintain the on-peak demand under a certain value during the entire on-peak rate period. The second control algorithm is an adjusting demand threshold MPC (ADT-MPC). ADT-MPC can better deal with unpredictable solar generation and/or changing building loads. The on-peak threshold under this algorithm is adjusted to the optimal value during the on-peak rate period. As expected, The CT-MPC algorithm performs well when coupled with accurate forecast models while the ADT-MPC algorithm excels when forecasting is more unpredictable.