Monday, May 22nd

Session I


T1

Quantifying Analyte-Porous Silicon Interactions

Ari Darlow Justin M. Reynard, Dustin T. McCall, Frank V. Bright

 University at Buffalo, Department of Chemistry

Porous silicon (pSi) has been studied for use in chemical sensing. Key to the success of such a strategy is to understand and selectively control analyte-pSi interactions. Toward these ends, we have been using the intrinsic pSi photoluminescence (PL) to determine the analyte-dependent PL response from as prepared and oxidized pSi (ap-, ox-pSi). Although these experiments provide some insights, they do not provide details into exactly how the analyte interacts with the Si nanocrystallites. To rectify this issue we have performed time-dependent Fourier transform infrared (FTIR) experiments under analyte flow to following the effects of analyte uptake and release within the pSi matrix and on the nanocrystallite surface Si-O-Si and SiHx (x = 1-3) residues. The combination of PL and FTIR experiments allow us to determine how the analyte interacts with the nanocrystallites to yield the analyte-dependent PL response. This presentation will summarize our most recent experiments.

T2

Investigating Organonitrogen Pesticides on Mineral Surfaces via Surface-Selective Vibrational Spectroscopy

Leander Bromley III, Luis Velarde, Jerry Cartagena, Dania Abdelhussein and Natalie Esadah

University at Buffalo, Department of Chemistry

According to the Environmental Protection Agency, over one billion pounds of pesticides are used in the United States annually.  Organonitrogen pesticides are currently amongst the most prevalently employed pesticide classes.  However, little is known about how interactions with, and modifications catalyzed by, leaf and soil surfaces affect their environmental fate.  Here, two such pesticides, carbaryl and propoxur are studied via SFG vibrational spectroscopy at the air/solid interface after being deposited on a fused quartz substrate, which serves as a model system for soil silica.  Despite being similar in structure and composition, the results obtained thus far suggest that the two pesticides interact with mineral surfaces differently, with carbaryl exhibiting a greater propensity for self-assembling into supramolecular aggregates than propoxur."

T3

GaIn Eutectic Masking during Porous Silicon Formation Creates Unique Spatially-Dependent Chemistries

Crystal Collado, Frank V. Bright

University at Buffalo, Department of Chemistry

Porous silicon (pSi) has been explored as a platform for multi-analyte detection. Previous research from our laboratory has shown that one can use GaIn eutectic to create interesting crystalline Si/porous silicon (cSi/pSi) platforms that exhibit unique analyte-dependent photoluminescence (PL) responses. This presentation focuses on characterizing these cSi/pSi interfaces by using profilometry, wide-field multispectral PL microscopy, and Fourier transform infrared (FTIR) microscopy. As we move along a vector from the cSi-pSi interface out into “bulk” pSi, our results reveal that the: (i) pSi thickness systematically increases; (ii) the PL emission maximum blue shifts; and (iii) relative SiHx (x=1-3) and OySiH (y=2,3) surface chemistries change. This presentation will summarize our most recent results and interpretations.

  T4

Rational Design of Multi-Functional Pyrylium Dye Compounds

Konstantinos Plakas, Chrysafis Andreou, Moritz Kircher, Stefan Harmsen and Michael R. Detty

University at Buffalo, Department of Chemistry

The synthesis and applications of dye molecules has fascinated chemists for over a century.  Applications of synthetic dyes are vast, and are of interest to textile industry, molecular imaging, and renewable imaging.  Recent developments in biomedical imaging and materials chemistry has necessitated the synthesis of tailored designer dyes.  Specifically, Surface-Enhanced Raman Scattering (SERS) requires spectroscopically unique chromophores to permit multiplexing of convoluted biological tissues.  Currently, the user is limited to a handful of commercially available dyes, precluding the true multiplexing capabilities of SERS from being realized.  The pyrylium dye class has long been known, and possess several functionalizable moieties that enable control over photophysical and photochemical properties.  Namely, the incorporation of heavy chalcogen atoms confer affinity for gold and silver nanopoarticles typically used in SERS assays.  Furthermore, these dyes can be tailored to incorporate several different Raman active functional groups, enabling synthesis of spectroscopically unique dyes.  An additional benefit is that the absorption of these pyrylium dyes can be tuned from the near infrared to infrared.  Compatibility with NIR excitation sources permit deep tissue penetration and minimizes scattering from biological tissue. Herein, the synthesis of novel near infrared absorbing pyrylium will be described.

T5

Impact of Laser Exposure and Power on Single- and Few-Layer WS2

Samantha Matthews, Chuan Zhao, Hao Zeng and Frank V. Bright

University at Buffalo, Department of Chemistry

Single- and few-layer transition metal dichalcogenides (TMDCs) are mainly characterized by layer thickness, chemical composition, and exciton contribution using atomic force microscopy (AFM), Raman, and photoluminescence (PL) techniques, respectively. Raman and PL measurements necessitate that the sample be exposed to laser radiation for various time periods. What is the impact of laser power and time on the WS2? This presentation will summarize recent research exploring the role of laser power and exposure time on the observed PL emission, Raman spectra, and topography from WS2 on sapphire.