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Program Highlights

One-Step Synthesis of Fluorescent Graphene Quantum Dots Through Pyrolysis of Amino Acids

August 21, 2017

Outcome: We have developed a novel method for the synthesis of graphene quantum dots (GQDs) by using two amino acids, which are non-toxic natural materials containing nitrogen groups for easy surface modification. The synthesis process was easy, efficient and no toxic chemicals were involved. The obtained GQDs had a size of 3.26± 1.30 nm and lattice spacing of 0.286 nm.

Impact: These GQDs emitted strong blue fluorescence, demonstrated high photostability and showed tunable emission wavelength by changing the excitation wavelength, which have great potentials in biomedical imaging, designs of biosensors, and etc. Moreover, they had good solubility not only in water, but also in many organic solvents, which may future broaden their applicability. Dissolved in different solvents did not affect their fluorescence emission ability.

A Pressure-Induced Emergence of a Weyl Semimetal Phase in Pb1-xSnxTe

August 21, 2017

Outcome: In collaboration with experimental studies at Princeton University we have carried out ab initio calculations to examine the effect of pressure on the topological phase diagram of Pb1-xSnxTe. The calculations reveal that the ferroelectric polarization, which breaks crystal inversion symmetry, induces a Weyl semimetallic state separating the normal insulator and topological crystalline insulator phases. The metallic phase features pairs of Weyl nodes of opposite chiralities which persist over a finite pressure range. Hence the metallic phase is protected since the Weyl nodes cannot be removed except by mutual annihilation which occurs at higher pressure.

Polymer/Carbon Spheres Composites for Device Applications

August 21, 2017

Intellectual Merit: Carbon-based materials have attracted scientific interest due to their promise to revolutionize the electronics industry. Carbon Spheres (CS) were produced via hydrothermal carbonization of sucrose. A Schottky diode was fabricated using a composite of the highly conductive CS and the polymer PEO (polyethylene oxide). The diode was tested as a half wave rectifier. The simple design and fabrication, and complete exposure of the carbon material to the ambient make these diodes excellent candidates for use in active electronic components including gas/light sensors.

PREM Collaborators: Students: Cesar Nieves, Luis Martínez, José L. Pérez-Gordillo. Faculty: Idalia Ramos, Nicholas Pinto, Natalya Zimbovskaya, Margarita Ortiz (UPRH) and Jorge Santiago (PENN). 

Broader Impacts: This is the first study demonstrating real applications using conducting carbon spheres fabricated via an easy, rapid, cheap, and green technique.

Integrated 3D printing with in-situ functionalization of piezoelectric nanocomposites

April 5, 2017

Our research supported by the NSF PREM project studied the synthesis, fabrication, and characterization of advanced materials for sensing, energy harvesting, and storage.

Our integrated 3D printing with in-situ functionalization of piezoelectric nanocomposite enabled us design nanocomposites with engineered properties towards different applications such as pressure sensing, self-cleaning, steam harvesting, vibration and thermal energy harvesting.  Our research results generated 5 journal (1 accepted, 4 under review) papers this reporting period, and 1 proposal funded by DOE. 

New Fullerene Derivatives for Electron Transporting Materials in Inverted Planar Perovskite Solar Cells

April 5, 2017

Perovskite solar cells (PSCs), have shown a remarkable increase in photoconversion efficiency (PCE), from 3.8%  in 2009, to 22.1% in 2016. The good electron transporting and solution processable properties of most fullerene derivatives make them the most popular electron transporting materials (ETMs) in PSCs. To the best of our knowledge, the influence of different adducts on the PCEs of fullerene-based PSCs has not been fully explored to date. Here, we report  new functionalized fullerene derivatives, and their performance as the ETMs in PSCs. 

What happens to photogenerated charges in semiconductor nanowires?

July 6, 2016

How? We use optical microscopy to determine the dynamics of photo-generated charges in individual semiconductor nanowire hetero-structures.

Development of chemical and biological sensors: Synthesis of Plasmonic Nanoparticles and Multispectral Imaging Nanostructures

July 6, 2016

How? Synthesizing and isolation of ultra-small gold nanoparticles with a specific shape or structure. We have developed a facile approach for shape-controlled synthesis of gold nanoparticles using KBr and 5-hydroxyindoleacetic acid (5-HIAA) as the reducing agent. 

Investigation of Indium Free Transparent Conducting Oxides for Application in Photovoltaics

September 11, 2015

Transparent conducting oxide play a key role in photovoltaic (PV) devices. There has been much recent interest in finding alternative indium (In) free TCOs and even better performing alternative candidates to substitute for standard ITO.  The driving factors are: scarcity, unintended interfacial phenomena, rapid price increase and global politics associated with In metal in ITO. TCOs based on titanium (Ti) doped tungsten oxide (WO3) thin films were studied in this project. X-ray photoelectron spectroscopy (XPS) analyses provided the chemical and electronic structure changes in the Ti-doped WO3 thin films. The studies when combined with optical studies enabled engineering the materials with desired TCO properties.

Synthesis of Fullerene Derivatives for Potential Applications in OPV Devices

September 11, 2015

We have separated Sc3N@D5h-C80 from Sc3N@C68 based on their chemical reactivity differences using the p-toluenesulfonyl tosyl hydrazone of phenyl butyric acid methyl ester (PCBM). We also performed for the first time the synthesis and characterization of five PCBM methano-derivatives of Sc3N@D5h-C80 (including the X-ray diffraction structure of one of the isomers) and two PCBM methano-derivatives of Sc3N@C68.

We also synthesized four easily isolable regio and stereoselective pure bis-adducts of C60 and C70 and a new C70 dumbbell using two different malonate tethered moieties.

Humacao PREM visits Rural Schools

August 5, 2015

In March-April 2015, approximately 50 PREM students, faculty and other volunteers visited six rural schools in the towns of Yabucoa and San Lorenzo, Puerto Rico. The activities included short talks and hands-on demonstrations from the Nanodays (NISENet) kits and others developed by our program. Over 800 students, teachers and parents participated in this effort to reach minority and geographically isolated communities. 

 

 

Bubble formation in chloroform at negative pressures

August 5, 2015

The aim of this project if to detect and characterize nucleation sites when a local cavity starts to form, in particular to detect cavitation sites in molecular dynamics simulations of liquid chloroform with and without carbon nanotubes.

Ultraviolet Tunable MoS2/p-Silicon Junction Diode

August 4, 2015

MoS2 single crystals were transferred onto the edge of a p-Si/SiO2 wafer, forming an abrupt heterogeneous junction diode at the MoS2/p-Si interface. When electrically characterized as a field effect transistor, MoS2 exhibits an n-type response and can be doped in the presence of ultraviolet (UV) light. Its simple design coupled with the ability to rectify AC signals, sense UV light, and reversibly tune these diodes makes them inexpensive, multifunctional, and usable as active or passive components in complex electronics.




 

Hysteretic Adsorption of CO2 onto a Cu2(pzdc)2(bpy) Porous Coordination Polymer and Concomitant Framework Distortion

August 4, 2015

In a recent publication resulting from a collaboration between the IRG2 of the Wisconsin MRSEC and the University of Puerto Rico Mayaguez through the NSF-sponsored Partnerships for Research and Education in Materials (PREM) program, Prof. Hernandez-Maldonado and coworkers investigated the structural mechanisms of the hysteretic adsorption of carbon dioxide onto the porous coordination polymer, CPL-2. CPL-2 is currently under investigation for industrial-scale carbon dioxide capture applications.

Combination treatment with synthetic β-peptide enhances the antifungal activities of azoles in Candida albicans

August 4, 2015

Fungal infections such as candidiasis represent an important human health concern worldwide due to high mortality rates, of more than 50%, specifically in those people who are immunocompromised.  In particular risk are those patients undergoing chemotherapy, that suffer from AIDS and those who receive an organ transplant.  Other concerns include the side effects of the current antifungal drugs and the emergence of multidrug resistant organisms. 

Do “Hot” Charge-Transfer Excitons Promote Free Carrier Generation?

August 4, 2015

In organic photovoltaics, the role of hot charge-transfer (CT) excitons on free carrier generation is currently under intense debate. In this project, we carry out first-principles time-dependent density functional theory calculations to examine hot CT dissociation in polymer/fullerene heterojunctions. We reveal that whether or not hot CT states promote charge separation depends on excitation spectral range and crystallinity of the donor and acceptor phases. We find that while the crystallinity of the donor phase underlies the energy dependence of CT exciton dissociation, the crystallinity of the acceptor determines charge separation efficiency. We propose a theory that can reconcile contradictory experimental observations and provide insight into hot CT dissociation. Crucially, the timescale of hot CT dissociation is found to be comparable to the timescale of its relaxation to the lowest-lying CT state, which is localized in all interfacial models studied.

 

Nanotechnology Exhibition for Junior High School Participants

August 1, 2015

NSF-JSU-UCSB PREM members conducted outreach activities at local school and initiate a Science Line program to the minority participants.

Plasmonic–Magnetic 3D Graphene Oxide Architecture Can Pick and Separate Rotavirus

August 1, 2015

According to the World Health Organization (WHO), more than 1.5 million children die each year due to rotavirus contamination in drinking water.

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