Metamaterials and metasurfaces can be seen as a novel approach for constructing practical quantum photonic systems. In this talk, we present our recent advances in controlling single-photon emission from nitrogen-vacancy (NV) color centers in nanodiamonds using CMOS-compatible hyperbolic metamaterials. Further, we discuss how an increased photonic density of states affects the optical readout of the NV center spin-state. These results can be useful for engineering on-chip room-temperature quantum registers.
KEYWORDS: Luminescence, Diamond, Quantum information, Plasmonics, Solid state electronics, Information technology, Nanocrystals, Video, Metamaterials, Current controlled current source
Diamond based nitrogen-vacancy (NV) centers are promising solid state defects for applications in quantum information technologies. On the one hand, there is a growing interest in enhancing their single-photon emission by coupling them to plasmonic structures. On the other hand, the dependence of emission intensity on the electron spin state enables room temperature quantum information readout. We study the fluorescence contrast resulting from the spin resonance in the conditions of an increased photonic density of states. Fluorescence observations from NV center ensembles in diamond nanocrystals coupled to structures supporting plasmonic modes experimentally confirm the analytical results.
Fluorescence-based single molecule techniques to interrogate gene expression in tissues present a very low signal-to-noise ratio due to the strong autofluorescence and other background signals from tissue sections. This report presents a background-free method using second-harmonic generation (SHG) nanocrystals as probes to quantify the messenger RNA (mRNA) of human epidermal growth receptor 2 (Her2) at single molecule resolution in specific phenotypes at single-cell resolution directly in tissues. Coherent SHG emission from individual barium titanium oxide (BTO) nanoprobes was demonstrated, allowing for a stable signal beyond the autofluorescence window. Her2 surface marker and Her2 mRNA were specifically labeled with BTO probes, and Her2 mRNA was quantified at single copy sensitivity in Her2 expressing phenotypes directly in cancer tissues. Our approach provides the first proof of concept of a cross-platform strategy to probe tissues at single-cell resolution in situ.
Cell-specific information on quantity and localization of key mRNA transcripts in single-cell level are critical to the assessment of cancer risk, therapy efficacy, and effective prevention strategies. However, most available technologies for mRNA detection rely on cell extraction that inherently destroys the tissue context and provide only average expression levels from cell populations or whole tissues. In this paper, we proposed a novel super resolution concept, second harmonic generation (SHG) super-resolution microscopy (SHaSM), and apply that to detect single short mRNA transcript, Her2 mRNA, beyond the diffraction limit. Nano-sized SHG crystals, barium titanium oxide BaTiO3 (BTO), were functionalized with two complimentary strands of Her2 mRNA after the chemical surface-modification. Dimer schematic was used to improve the specificity of detection and quantification, where two BTO monomers bind to the Her2 mRNA to form a dimer and being visualized via the SHaSM. SHaSM is able to detect single BTO nanocrystal with ~20 nm spatial resolution, and differentiate BTO dimers (Her2 mRNA) from BTO monomers (non-specific bounded BTO nanocrystal) with high specificity.
Engineering of quantum emissions is regarded as the heart of nano-optics and photonics; local density of optical states (LDOS) around the quantum emitters are critical to engineer quantum emissions, thus detection of the LDOS will impact areas related to illumination, communication, energy, and even quantum-informatics. In this report, we demonstrated a far-field approach to detect and quantify the near-field LDOS of a nanorod via using CdTe quantum dots (QDs) tethered to the surface of nanorods as beacons for optical read-outs. The spontaneous decay of QD emission in the proximity of nanorod was used as a ruler for elucidating the LDOS. Our analysis indicates that the LDOS of the nanorod at its ends is 2.35 times greater than that at the waist. Our approach can be applied for further evaluation and elucidation of the optical states of other programmed nanostructures.
KEYWORDS: 3D modeling, Tumor growth modeling, Breast cancer, Raman spectroscopy, Cancer, Data modeling, Principal component analysis, Chemical analysis, Statistical analysis, Tumors
We demonstrate the first application of Raman spectroscopy in diagnosing nonmalignant, premalignant, malignant, and metastatic stages of breast cancer in a three-dimensional (3-D) cell culture model that closely mimics an in vivo environment. Comprehensive study comparing classification in two-dimensional (2-D) and 3-D cell models was performed using statistical methods composed of principal component analysis for exploratory analysis and outlier removal, partial least squares discriminant analysis, and elastic net regularized regression for classification. Our results show that Raman spectroscopy with an appropriate classification tool has excellent resolution to discriminate the four stages of breast cancer progression, with a near 100% accuracy for both 2-D and 3-D cell models. The diversity in chemical groups related to nucleic acids, proteins, and lipids, among other chemicals, were identified by appropriate peaks in the Raman spectra that correspond to the correct classification of the different stages of tumorigenesis model comprising of MCF10A, MCF10AneoT, MCF10CA1h, and MCF10CA1a cell lines. An explicit relationship between wavenumber and the stages of cancer progression was identified by the elastic net variable selection.
A one-step rapid and ultrasensitive immunoassay capable of detecting proteins in blood serum is developed using gold nanoprobes and fluorescence correlation spectroscopy (FCS). In this approach we take advantage of the inherent photoluminescence property of gold nanoparticles (GNPs) to develop a fluorophore-free assay to observe binding entities by monitoring the diffusion of bound versus unbound molecules in a limited confocal volume. 40-nm GNPs conjugated separately with rabbit anti-IgG (Fc) and goat anti-IgG (Fab) when incubated in blood serum containing IgG forms a sandwich structure constituting dimers and oligomers that can be differentiated by to detect IgG in blood serum at a limit of detection (LOD) of 5 pg/ml. The novelty of integrating GNPs with FCS to develop a sensitive blood immunoassay brings single molecule methods one step closer to the clinic.
Gold nanoparticles grown within the intracellular confines of living cells are introduced as potential surface-enhanced Raman scattering (SERS) substrates for confocal Raman spectrometry. Electron microscopy and a silver-enhanced reflectance laser scanning confocal microscopic approach were used to visualize the size, shape, and distribution of intracellularly grown gold nanoparticles (IGAuN) as small as 1 nm. Passive uptake as the conventional approach for delivering nanoparticles inside cells faces the insurmountable challenge of escaping the endosomal/lysosomal pathway. In contrast, IGAuN provides an unprecedented advantage of providing access to cytoplasm and nucleus.
Thin film multi-layered chalcogenide glass waveguide structures have been fabricated for evanescent wave sensing of bio toxins and other applications. Thin films of Ge containing chalcogenides have been deposited onto Si substrates, with a-GeSe2 as the cladding layer and a-GeSbSe as the core layer to form the slab waveguide. Channel waveguides have been written in the slab waveguides by appropriate light the through a mask. The photo-induced structural changes in the core layer selectively enhance refractive index at the portions of interest and thus confining the light to the channels. The waveguides have been characterized and tested for the guiding of light.
The purpose of this study is to produce a platform device with the ability to detect a variety of pathogens based upon antigen-antibody interactions. The sensor comprises a nanoporous GeSe channel waveguide fabricated on a substrate, with an intermediate cladding buffer layer [GeSe2], which is required when the substrate does not transmit at the desired λ. The light from a laser source is then coupled through a fiber and prism into the waveguide and collected with the help of a lens into a detector. The top cladding layer is a Ge28Sb12Se60 thin film in which biomolecules can be 'tethered' via functionalization of the surface. Therefore the surface chemistry of the thin film and the specificity of antibody to its antigen are important considerations. This paper will focus primarily on the surface characterization of the top cladding layer using XPS, AFM, ellipsometry, contact angle measurements and diffuse reflectance analysis.
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