Combined Apertureless Near-Field Optical Second-Harmonic Generation/Atomic Force Microscopy Imaging and Nanoscale Limit of Detection

Meyer, Kent A.; Ng, Kin C.; Gu, Zhanjun; Pan, Zhengwei; Whitten, William B.; Shaw, Robert W.

doi:10.1366/000370210790572070

Cited by 10 publications

(15 citation statements)

References 20 publications

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“…The observed overall decrease in SHG signal is consistent with previous reports using SHG imaging techniques to study ZnO nanowire corrosion, where the formation of carbonates, which are not SHG active, resulted in a decrease in SHG intensity. 92,93 In the case of CdSe QDs, oxidation can form SeO 2 and CdO products, 87 thereby producing a layer of SHG inactive material at the surface. The formation of interfacial oxides changes the nonlinear susceptibilities of surface-like states more severely than those consisting mostly of contributions from interior atoms of the QDs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Probing Interfacial Electronic States in CdSe Quantum Dots Using Second Harmonic Generation Spectroscopy

Doughty

Shaw

2015

J. Phys. Chem. C

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Understanding and rationally controlling the properties of nanomaterial surfaces is a rapidly expanding field of research due to the dramatic role they play on the optical and electronic properties vital to light harvesting, emitting, and detection technologies. This information is essential to the continued development of synthetic approaches designed to tailor interfaces for optimal nanomaterial-based device performance. In this work, closely spaced electronic excited states in model CdSe quantum dots (QDs) are resolved using second harmonic generation (SHG) spectroscopy, and the corresponding contributions from surface species to these states are assessed. Two distinct spectral features are observed in the SHG spectra, which are not readily identified in linear absorption and photoluminescence excitation spectra. These features include a weak band at 395 ± 6 nm, which coincides with transitions to the 2S1/2 1Se state, and a much more pronounced band at 423 ± 4 nm arising from electronic transitions to the 1P3/2 1Pe state. Chemical modification of the QD surfaces through oxidation resulted in disappearance of the SHG band corresponding to the 1P3/2 1Pe state, indicating prominent surface contributions. Signatures of deep trap states localized on the surfaces of the QDs are also observed. We further find that the SHG signal intensities depend strongly on the electronic states being probed and their relative surface contributions, thereby offering additional insight into the surface specificity of SHG signals from QDs.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Probing Interfacial Electronic States in CdSe Quantum Dots Using Second Harmonic Generation Spectroscopy

Doughty

Shaw

2015

J. Phys. Chem. C

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“…The gold-coated tip, of diameter 70 nm, was reported to enhance the SHG signal from individual ZnO nanowire by a factor of 2000, after accounting for the far-field background signal. 289 A strong polarization dependence was observed on the SHG signal. 283-286, 289, 290 Excitation with p-polarization resulted in a stronger near-field SHG signal.…”

Section: Second-harmonic Generationmentioning

confidence: 91%

Invited Review Article: Combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

Lucas

Riedo

2012

Review of Scientific Instruments

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This is a comprehensive review of the combination of scanning probe microscopy (SPM) with various optical spectroscopies, with a particular focus on Raman spectroscopy. Efforts to combine SPM with optical spectroscopy will be described, and the technical difficulties encountered will be examined. These efforts have so far focused mainly on the development of tip-enhanced Raman spectroscopy, a powerful technique to detect and image chemical signatures with single molecule sensitivity, which will be reviewed. Beyond tip-enhanced Raman spectroscopy and/or topography measurements, combinations of SPM with optical spectroscopy have a great potential in the characterization of structure and quantitative measurements of physical properties, such as mechanical, optical, or electrical properties, in delicate biological samples and nanomaterials. The different approaches to improve the spatial resolution, the chemical sensitivity, and the accuracy of physical properties measurements will be discussed. Applications of such combinations for the characterization of structure, defects, and physical properties in biology and materials science will be reviewed. Due to the versatility of SPM probes for the manipulation and characterization of small and/or delicate samples, this review will mainly focus on the apertureless techniques based on SPM probes.

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“…A ZnO NW was characterized before and after exposure to carbon dioxide and water vapor using a NF, tip-enhanced SHG imaging microscope. This nonlinear imaging instrument 26 provides FF, NF, and AFM images of nanoscale objects. The resolution of the microscope allowed discovery of an unexpected nonuniform degradation of the ZnO NW.…”

Section: ■ Introductionmentioning

confidence: 99%

Nanoscale Chemical Imaging of Zinc Oxide Nanowire Corrosion

et al. 2012

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The ability to monitor corrosion on a nanometer scale is a powerful tool for a fundamental understanding of surface chemical processes. Nanoscale chemical images of individual bare and alumina-coated zinc oxide nanowires (NWs) were recorded using tip-enhanced second harmonic generation (SHG) spectroscopy before and after exposure to carbon dioxide and water vapor. Images were collected for the same bare nanowire after each successive two-day exposure period. Corrosion of the bare ZnO NW to zinc carbonate was evident from far-field and near-field SHG images and simultaneously recorded atomic force microscopy (AFM) data. The expected zinc carbonate corrosion product is SHG inactive. The AFM profile of the NW showed vertical and lateral expansion in different regions of the nanowire. The lower resolution far-field SHG signal decreased gradually and uniformly. The near-field SHG signal provided a profile of the evolving NW with a spatial resolution approaching 100 nm. In contrast, exposed alumina-coated ZnO NWs showed reduced, but still observable, degradation. The 3 nm thick alumina protective layer may have been insufficient to fully protect the NW, or the coating may have been incomplete. Thicker coatings preclude the tip-enhanced method. Further nanometer-scale imaging should lead to the discovery of protective layers to prevent or delay ZnO degradation.

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Combined Apertureless Near-Field Optical Second-Harmonic Generation/Atomic Force Microscopy Imaging and Nanoscale Limit of Detection

Cited by 10 publications

References 20 publications

Probing Interfacial Electronic States in CdSe Quantum Dots Using Second Harmonic Generation Spectroscopy

Probing Interfacial Electronic States in CdSe Quantum Dots Using Second Harmonic Generation Spectroscopy

Invited Review Article: Combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

Nanoscale Chemical Imaging of Zinc Oxide Nanowire Corrosion

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