editorial
Nanoparticles: An Emerged and Lasting Frontier
T
his Editorial is another in the series that applauds emerging frontiers of science and analytical chemistry. In this instance, the emergence neither occurred just yesterday nor will it end tomorrow; nanoparticles (NPs) will be part of the heart and soul of analytical chemistry and science at large, far off into the future. Although nanoscience has long been important, what has changed to make it even more meaningful is a combination of innovations in NP synthesis and measurement capabilities and increased federal support, based on the promise of the field. This is a potent combination. Analytical chemists have been significant innovators in NP synthesis and measurement capabilities. What are some essential features of NPs that provide them with important analytical and scientific capacity? For reactions or applications dependent on interfacial interactions, NPs offer large specific surface areas, whether they are organized into a film or dispersed as a solution. Many NPs form true solutions, a flexibility that allows especially easy access to their surfaces. NPs’ small dimensions allow them access to small spaces, which is particularly significant in biological contexts such as blood circulation, cell transfection, and excretion, and in molecular electronics contexts where small-space scaling is a driver of innovation. In biological and therapeutic contexts, smallness is insufficientOnegligible toxicity to the host is also vital. In any application, from catalysis to electrocatalysis to analytical sensors to biological cell transfection, NPs (whether composed of semiconductor, metallic, metal oxide, or polymeric materials) must offer a stable composition or behavior, or one that can be predictably altered. NPs should be reasonably priced and easy to synthesize; this can make or break an application. At some size, NPs transition from bulk material to individual molecules, which leads to size-dependent (as opposed to composition-dependent) properties that have both fundamental and technological importance. In an analytical context, NP design must include a readout analyte response property, either directly or through some other chemical system. Exploration and application of NPs are advancing science in quite diverse areas. The strong, adjustable optical absorbance of an NP can allow it to intensely absorb and thermally
10.1021/AC900238P 2009 AMERICAN CHEMICAL SOCIETY
Published on Web 02/11/2009
disperse laser pulses, as is desired in MALDI MS. The sensitivities of surface plasmon excitations to the dielectric properties of the adjacent medium allow detection of surface binding events. In electrocatalysis and energy storage, the large area and chemically adjustable surfaces of NPs provide important energy technology for fuel cells, batteries, and supercapacitors. NPs can be tools in tissue imaging, through their effects on NIR emission, electron beam scattering, and nuclear spin relaxation, among others. NPs can be loaded with multiple reagents and highly specific binding sites. When such multiplicity is partnered with enzymes or metal depositions, it can strongly amplify analyte binding and yield extraordinarily large sensitivities. NPs coated with monolayer stationary phases can be used to aid separations in CE in a manner similar to micellar hosts. Many other examples exist. As important as these applications are or may become, researchers sometimes charge into NP use with inadequate attention to what the NPs actually are. When used as chemical substances, or carriers thereof, NPs should not be deployed in ignorance of their composition and, ultimately, structure. NP analysis can be challenging, but advances are steadily being made, and providing solely a transmission electron microscopy-based diameter should no longer be an acceptable practice. Analytical chemists should feast on the numerous opportunities to contribute in this arena. The American Chemical Society journal family has strongly capitalized on nanoscience as a theme, including in recent new journals. Analytical Chemistry has a long-standing interest in nanoscienceOit is a terrifically important part of measurement science. This Editor wants to make it abundantly clear to authors of papers on analytical and measurement nanoscience that Analytical Chemistry welcomes submission of their research progress.
MARCH 1, 2009 / ANALYTICAL CHEMISTRY
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