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The ability to combine microscopy and spectroscopy is beneficial for directly monitoring physical and biological processes. Spectral imaging approaches, where a transmission diffraction grating is placed near an imaging sensor to collect both the spatial image and spectrum for each object in the field of view, provide a relatively simple method to simultaneously collect images and spectroscopic responses on the same sensor. Initially demonstrated with fluorescence spectroscopy, the use of spectral imaging in Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) can provide a vibrational spectrum containing molecularly specific information that can inform on chemical changes. However, a major complication to this approach is the spectral overlap that occurs when objects are spaced closely together horizontally. In this work, we add a dove prism to a spectral imaging instrument developed for SERS imaging, enabling rotation of the collected SERS image and dispersed spectrum onto the imaging complementary metal-oxide semiconductor (CMOS) sensor. We demonstrate that this effectively reduces spectral overlap for emitters with clear separation between them and emitters with slightly overlapping point spread functions thereby facilitating collection of unambiguous spectra from each emitter. 

Strongly confined electric fields resulting from nanogaps within nanoparticle aggregates give rise to significant enhancement in surface-enhanced Raman scattering (SERS). Nanometer differences in gap sizes lead to drastically different confined field strengths, so much attention has been focused on the development and understanding of nanostructures with controlled gap sizes. In this work, we report a novel petal gap-enhanced Raman tag (GERT) consisting of bipyramid core and a nitrothiophenol (NTP) spacer to support the growth of hundreds of small petals and compare its SERS emission and localization to a traditional bipyramid aggregate. To do this, we used super resolution spectral SERS imaging that simultaneously captures the SERS images and spectra while varying the incident laser polarization. Intensity fluctuations inherent of SERS enabled super resolution algorithms to be applied which revealed sub-diffraction limited differences in the localization with respect to polarization direction for both particles. Interestingly, however, only the traditional bipyramid aggregates experienced a strong polarization dependence in their SERS intensity and in the plasmon-induced conversion of NTP to dimercaptoazobenzene (DMAB), which was localized with nanometer precision to regions of intense electromagnetic fields. The lack of polarization dependence (validated through electromagnetic simulations) and surface reactions from the bipyramid-GERTs suggest that the emissions arising from the bipyramid-GERTs are less influenced by confined fields. 

SERS substrates with silver nanosheets (AgNS) on a copper surface were synthesized. A quantitative analysis of the pesticide imidacloprid was then performed by applying a PLSR chemometric model. 

Advances in nanotechnology enable the detection of trace molecules from the enhanced Raman signal generated at the surface of plasmonic nanoparticles. We have developed technology to enable super-resolution imaging of plasmonic nanoparticles, where the fluctuations in the surface enhanced Raman scattering (SERS) signal can be analyzed with localization microscopy techniques to provide nanometer spatial resolution of the emitting molecule’s location. Additional work now enables the super-resolved SERS image and the corresponding spectrum to be acquired simultaneously. Here we will discuss how this approach can be applied to provide new insights into biological cells. 

Fouling at interfaces deteriorates the efficiency and hygiene of processes within numerous industrial sectors, including the oil and gas, biomedical device, and food industries. In the food industry, the fouling of a complex food matrix to a heated stainless steel surface reduces production efficiency by increasing heating resistance, pumping requirements, and the frequency of cleaning operations. In this work, quartz crystal microbalance with dissipation (QCM-D) was used to study the interface formed by the fouling of milk on a stainless steel surface at different flow rates and protein concentrations at high temperatures (135 °C). Subsequently, the QCM-D response was recorded during the cleaning of the foulant. Two phases of fouling were identified. During phase-1, the fouling rate was dependent on the flow rate, while the fouling rate during phase-2 was dependent on the flow rate and protein concentration. During cleaning, foulants deposited at the higher flow rate swelled more than those deposited at the lower flow rate. The composition of the fouling deposits consisted of both protein and mineral species. Two crystalline phases of calcium phosphate, β-tricalcium phosphate and hydroxyapatite, were identified at both flow rates. Stratification in topography was observed across the surface of the QCM-D sensor with a brittle and cracked structure for deposits formed at 0.2 mL/min and a smooth and close-packed structure for deposits formed at 0.1 mL/min. These stratifications in the composition and topography were correlated to differences in the reaction time and flow dynamics at different flow rates. This high-temperature application of QCM-D to complex food systems illuminates the initial interaction between proteins and minerals and a stainless steel surface, which might otherwise be undetectable in low-temperature applications of QCM-D or at larger bench and industrial scales. The methods and results presented here have implications for optimizing processing scenarios that limit fouling formation while also enhancing removal during cleaning.