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Nanomaterials in Analytical Chemistry

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A particularly intriguing incentive for developing new approaches to nanomaterials fabrication is the potential for creating new constructs with nanoscale order and unique functional properties. Nanomaterials for analysis can be constructed with the manipulation of one or more components. Single-component architectures for sensing include metal organic frameworks for detection of explosives, metal organic polymers for enzyme immobilization, steam-etched graphene oxide networks for NO2 detection, carbon ring microelectrode arrays for single cell imaging, and 2D photonic crystal sensors. Assemblies of single components include gold nanoclusters for detection of dopamine, layered graphene coatings for microextraction, polymer nanoparticles embedded in a membrane for sensing lead, and carefully spaced silver nanoparticles for surface enhanced Raman spectroscopy. An example of a recognition molecule attached to such a single-component nanomaterial is provided by the description of recognition by a molecular beacon attached to graphene oxide. As the tools for assembling single-component architectures become available, multiple materials are combined to form more complex nanomaterials designed to perform a greater diversity of measurements. Gold nanoparticles are welded to graphitic templates for sensing hydrogen sulfide, linked with quantum dots to produce a fluorescent signal in the presence of TNT or linked with cadmium sulfide films and aptamers for thrombin detection by electrochemiluminescence. Clusters of polymer micelles are formed using block copolymers and multiple fluorophores for pH sensing and proteins direct the formation of clusters of silver nanoparticles for sensing mercury. Even more complex assemblies of nanostructure components include the construction of light-controlled quantum dot electrodes for oxygen measurements and the lining of solid-state nanochannels with DNA to create nanofluidic logic structures. As better and better nanomaterials are developed for analysis, the resolution of possible analyses gets finer and finer. Single molecule analysis is a familiar goal, and success in this area is exemplified by single-molecule electrochemical gating in ionic liquids, screening of electrocatalysts using bipolar electrodes, and nanopores for measuring single DNA−polymerase complexes. In addition, surfaces are being interrogated using molecular rulers and real-time NMR to probe the electrical double layer and shell-isolated gold nanoparticles for enhancing Raman signals. Many analyses for which nanomaterials have been used are highly creative and just plain fun. Enjoy the descriptions of nanoparticles for imaging bank notes or the use of DNA as an invisible ink. Considerations of energetic properties of nanomaterials has led to biofuel cells implanted in living insects, nanomotors based on metallic nanobatteries, and ice as a platform for attoliter reactors. Chemiluminescent nanoparticles have been incorporated into paper-based microfluidic diagnostic systems. We challenge you to use the new scientific

he societal impact of materials structured at the nanometer scale is enormous and continues to increase at a remarkable pace. Particles of wide ranging chemistries are now routinely engineered and synthesized at the nanometer length scale to provide integral components for systems as diverse as medical therapeutics and diagnostics, energy harvesting and storage, textiles and construction, electronics and optics, and chemical synthesis and purification. It is thus not surprising that new methods of chemical analyses and sensing that take advantage of the unique properties of nanomaterials, as well as new methods for the analysis of nanomaterials themselves, are intense research areas for discovery. Nanomaterials have triggered the development of both new ways of performing target concentration and detection, and new analytical methods and instrumentation for measuring the properties of nanomaterials sensitive to changes at the nanometer or single molecule level. The optical and electronic properties of nanomaterials are often dominated by their surface chemistry and this makes the task of analyzing nanomaterials immensely more challenging than bulk materials or homogeneous solutions. Wolfgang Pauli’s quote “God made the bulk; surfaces were invented by the Devil” aptly describes both the challenges of analyzing nanoparticles and nanostrutures and the advantages of employing them in chemical analyses. This Virtual Issue assembles innovative papers from Analytical Chemistry and the Journal of the American Chemical Society in 2011 and 2012 that highlight discoveries in the assembly of nanomaterials, intriguing applications, and insightful methods of nanoscale analysis. By necessity, the ability to analyze nanoparticles has developed in concert with the fabrication of nanoparticles. In other words, to make reproducible nanomaterials for analysis, it is critical to be able to perform analyses at the nanometer scale. Very different approaches include the use of in situ X-ray diffraction and transmission microscopy to characterize particle changes in lithium−sulfur batteries, measurements of nanoparticle properties as they are transported through nanopores, and detection of collisions of single nanoparticles with ultramicroelectrodes. If subtle changes in nanoparticles can be measured, the nanoparticles can then be used for making measurements of interactive analytes in their immediate environment. Nanoparticles have been demonstrated to be useful for incredibly different kinds of analytes, including pH, ATP, microRNA, pesticides, proteins, and bacteria. Readout methods include impedance, colorimetry, fluorescence, Raman, and surface plasmon resonance. Nanoparticles are also proving extremely valuable in terms of providing new tools for analyzing targets in living cells and even in whole animals. Several papers describe new ways of addressing the tricky issue of getting the nanoparticles into the cells or attached to the cell surface, while other authors focus on the intracellular measurements. In several cases, the particles were modified to produce multiplexed measurements of multiple targets. © 2013 American Chemical Society

Published: December 3, 2013 11161

dx.doi.org/10.1021/ac403331m | Anal. Chem. 2013, 85, 11161−11162

Analytical Chemistry

Editorial

and analytical principles introduced in the papers referenced in this Virtual Issue to create unique and valuable analytical capabilities for the future.

Frances S. Ligler,† Associate Editor, Analytical Chemistry, Lampe Distinguished Professor of Biomedical Engineering Henry S. White,‡ Associate Editor, Journal of the American Chemical Society, Distinguished Professor and Chair †

Biomedical Engineering Department, North Carolina State University and University of North Carolina at Chapel Hill ‡ Department of Chemistry, The University of Utah

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dx.doi.org/10.1021/ac403331m | Anal. Chem. 2013, 85, 11161−11162

Nanomaterials in analytical chemistry.

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