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With arms radiating from a central core, gold nanostars represent a unique and fascinating class of nanomaterials from which extraordinary plasmonic properties are derived. Despite their relevance to sensing applications, methods for fabricating homogeneous populations of nanostars on large-area planar surfaces in truly periodic arrays is lacking. Herein, the fabrication of nanostar arrays is demonstrated through the formation of hexagonal patterns of near-hemispherical gold seeds and their subsequent exposure to a liquid-state chemical environment that is conducive to colloidal nanostar formation. Three different colloidal nanostar protocols were targeted where HEPES, DMF, and ascorbic acid represent a key reagent in their respective redox chemistries. Only the DMF-driven synthesis proved readily adaptable to the substrate-based platform but nanostar-like structures emerged from the other protocols when synthetic controls such as reaction kinetics, the addition of Ag + ions, and pH adjustments were applied. Because the nanostars were derived from near-hemispherical seeds, they acquired a unique geometry that resembles a conventional nanostar that has been truncated near its midsection. Simulations of plasmonic properties of this geometry reveal that such structures can exhibit maximum near-field intensities that are as much as seven-times greater than the standard nanostar geometry, a finding that is corroborated by surface-enhanced Raman scattering (SERS) measurements showing large enhancement factors. The study adds nanostars to the library of nanostructure geometries that are amenable to large-area periodic arrays and provides a potential pathway for the nanofabrication of SERS substrates with even greater enhancements. 

Falsified antimalarial pharmaceuticals are a worldwide problem with negative public health implications. Here, we develop a surface-enhanced Raman scattering (SERS) protocol to recognize substandard and falsified antimalarial drugs present in commercially available tablets. After recording SERS spectra for pure chloroquine, primaquine, and doxycycline, SERS is used to measure these drugs formulated as active pharmaceutical ingredients (APIs) in the presence of common pharmaceutical caplet excipients. To demonstrate the viability of our approach, a red team study was also performed where low-quality and falsified formulations of all three drugs presented as unknowns were identified. These data in conjunction with promising results from a portable Raman spectrometer suggest that SERS is a viable technique for on-site analysis of drug quality.