NERM 1

Using Raman spectroscopy to measure temperature increase in metal polymer nanocomposites due to thermoplasmonic effect Anatoli Ianoul, anatoli.ianoul@carleton.ca. Chemistry, Carleton University, Ottawa, Ontario, Canada

Properties of polymer/nanoparticle nanocomposites depend strongly on the nanoparticles density, aggregation state and embedment depth. When plasmonic nanoparticles are employed as nanocomposite fillers change in their plasmonic optical response can be used to monitor and to control most of these parameters. In this work, a simple process which uses a continuous-wave (CW) laser source to excite the LSPR of silver nanocrystals supported on polymer-thin films is used to fabricate desired nanocomposites. The delivery of heat into the supporting film results in a reduction in interfacial surface tension, which allows the nanocrystals to embed into the film. This results in a noticeable LSPR shift, enabling optically-printed patterns using only modest laser intensities of 5 kW/m2 . Using a metallic support (Ag, Au) of the polymer film allows for expanding of the colour palette by the creation of gap-modes between the particle/metal interface. At sufficient laser intensity direct ablation and lithography of the patterned film is also achieved. To determine the temperature of various heating regimes we used Stokes/anti-Stokes Raman spectroscopy, confirming the onset of embedment at the Tg of the polymer thin film. This work demonstrates a simple route to fabricate desired nanocomposites and to colour printing of plasmonic generated colour films.

NERM 2

Towards simultaneous elemental and molecular chemical imaging via combined laser-based optical and mass spectrometries Jacob T. Shelley, shellj@rpi.edu, Montwaun D. Young, Sunil Badal, Jessica Hellinger. Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, United States

The roles and characteristics of many materials, both manufactured and naturally occurring, depend on the material’s composition and morphological structure. The spatial distribution and identification of molecular and elemental species can assist in understanding the functions of many materials. Recent advances in analytical instrumentation and data capture/processing have led to the ability to generate comprehensive chemical maps (or “images”) of solid samples. Unambiguous analyte identification within these complex samples necessarily requires multiple analytical approaches performed on the same sample; these methods have been termed ‘multimodal chemical imaging’ approaches. While tandem imaging methods provide a wealth of information, they often suffer from weak sensitivity, poor selectivity, or compromised spatial resolution, as dictated by the spectroscopic method employed. Greater success in comprehensive chemical imaging has been achieved with instruments based around mass spectrometry (MS), due to the excellent sensitivity and selectivity; however, MS imaging is inherently destructive in nature. Here, we will present our recent work towards the development of a multimodal chemical imaging apparatus capable of simultaneously providing molecular and elemental information from the exact same spatial location at high spatial resolution (e.g., better than 30 μm). This dual imaging approach is achieved through laser ablation of samples at atmospheric pressure followed by simultaneous mass-spectrometric and optical-emission measurements. Aerosolized particles from the laser-ablation event were swept with a gas stream to a plasma-based molecular ionization source and, subsequently, mass-analyzed with an Orbitrap mass analyzer. At the same time, atomic emission from the laser-induced plasma formed during the ablation event was recorded with a fiber-coupled optical spectrometer to provide elemental information on the lasersampled area. The effect of various laser-ablation parameters, such as laser fluence and ablation-gas composition, in conjunction with ion source operating conditions were explored in detail. These parameters were found to influence atomic-emission and molecular-ion signals to different degrees. As such, approaches to obtain multimodal atomic and molecular images, as well as the data processing needed to generate and compare chemical images will be presented.

NERM 3

Freezing-induced gold nanoparticle (AuNP) aggregates: Potential applications for near-IR SERS substrates Kris Hoyt1 , Ashleigh Coggins1 , Igor K. Lednev2 , Jinseok Heo1 , heoj@buffalostate.edu. (1) Chemistry, State University of New York College at Buffalo, Buffalo, New York, United States (2) Univ of Albany Suny, Albany, New York, United States

Here we report the effect of freezing on the aggregation of citrate-capped gold nanoparticles (AuNPs). Separtate solutions of AuNPs with different average diameters (15, 30, 50, 70, and 100 nm) were frozen using either liquid nitrogen or a freezer and thawed slowly at room temperature. The drastic change of color in the AuNP solutions before and after a freezing-thawing process suggested the aggregation of AuNPs. We confirmed the freezing-induced AuNP aggregation using UV-VIS absorption spectroscopy, Raman spectroscopy, and SEM. The aggregation of AuNPs induced by a rapid freezing using liquid nitrogen is less extensive than that induced by a slow freezing using a freezer. This can be ascribed to the difference in the size of ice crystals depending on the freezing rate. The AuNPs are believed to be aggregated in the grain boundaries of those ice crystals. Thus, the aggregation of AuNPs is not so extensive in the grain boundaries of small ice crystals formed by a rapid freezing as in those of large ice crystals formed by a slow freezing. Among the tested AuNPs with different average diameters, the aggregates formed by the rapid freezing of 70 nm AuNP solution could be produced in a reproducible manner and stable for at least 3 months. They also showed mostly enhanced Raman signals in the near-IR region, which suggests they could be useful for near-IR SERS substrates.

NERM 4

Raman hyperspectroscopy is a universal tool for forensic purposes and medical diagnostics Igor K. Lednev, ilednev@albany.edu. University at Albany, State University of New York, Albany, New York, United States

Raman hyperspectroscopy combined with advanced statistics is uniquely suitable for characterizing microheterogeneous samples. Understanding the structure and (bio)chemical composition of samples at the microscopic level is important for many practical applications including material science, pharmaceutical industry, etc. We have recently demonstrated a great potential of Raman hyperspectroscopy for disease diagnostics and forensic purposes. In this presentation, we will discuss the development of a new, noninvasive method for Alzheimer’s disease (AD) diagnostics based on Raman spectroscopy of blood. Near infrared (NIR) Raman hyperspectroscopy coupled with advanced multivariate statistics was utilized for differentiating patients diagnosed with Alzheimer’s disease, other types of dementia and healthy control subjects with more than 95% sensitivity and specificity. When fully developed, this fast, inexpensive noninvasive method could be used for screening at risk patient populations for AD development and progression. Raman spectroscopy has already found numerous applications in forensic chemistry providing confirmatory identification of analytes. The technique is non-destructive, rapid and requires little or no sample preparation. Furthermore, portable Raman instruments are readily available allowing for crime scene accessibility. We have recently demonstrated that Raman microspectroscopy can be used for the identification of biological stains at a crime scene indicating the type of body fluid. In addition, peripheral and menstrual blood as well as human and animal blood can be differentiated. The time since deposition of bloodstain can be estimated up to two years. Most recently, we demonstrated the proof-of-concept for phenotype profiling based on Raman spectroscopy of dry traces of body fluids including the determination of sex and race of the donor.