Publications by authors named "Yung Doug Suh"

48 Publications

Purcell-enhanced photoluminescence of few-layer MoS transferred on gold nanostructure arrays with plasmonic resonance at the conduction band edge.

Nanoscale 2021 Mar;13(10):5316-5323

Laboratory for Advanced Molecular Probing (LAMP), Korea Research Institute of Chemical Technology, Daejeon 34114, South Korea. and School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, South Korea.

Plasmonic coupling of metallic nanostructures with two-dimensional molybdenum disulfide (MoS2) atomic layers is an important topic because it provides a pathway to manipulate the optoelectronic properties and to overcome the limited optical cross-section of the materials. Plasmonic enhanced light-matter interaction of a MoS2 layer is known to be mainly governed by optical field enhancement and the Purcell effect, while the discrimination of the contribution from each mechanism to the plasmonic enhancement is challenging. Here, we investigate photoluminescence (PL) enhancement from few-layer MoS2 transferred on Au nanostructure arrays with controlled localized surface plasmon resonance (LSPR) spectral positions that were detuned from the excitation wavelengths. Two distinctive regimes in LSPR mode-dependent PL enhancement were revealed showing a maximum enhancement (∼40-fold) with zero detuning and a modest enhancement (∼10-fold) with the red-shift detuned LSPR from the excitation wavelength, which were attributed to LSPR-induced optical field enhancement and the Purcell effect, respectively. By applying the experimental parameters into the Purcell effect formalism, an effective mode volume of ∼0.016λ03 was estimated. Our work provides an insight into how to utilize few-layer MoS2 as a base material for optoelectronics by harnessing Purcell-enhanced optical responsivity.
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http://dx.doi.org/10.1039/d0nr08158bDOI Listing
March 2021

Fabrication of plasmonic arrays of nanodisks and nanotriangles by nanotip indentation lithography and their optical properties.

Nanoscale 2021 Mar;13(8):4475-4484

Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science, Daejeon 34113, South Korea.

Fabrication of plasmonic nanostructures in a precise and reliable manner is a topic of huge interest because their structural details significantly affect their plasmonic properties. Herein, we present nanotip indentation lithography (NTIL) based on atomic force microscopy (AFM) indentation for the patterning of plasmonic nanostructures with precisely controlled size and shape. The size of the nanostructures is controlled by varying the indentation force of AFM tips into the mask polymer; while their shapes are determined to be nanodisks (NDs) or nanotriangles (NTs) depending on the shapes of the AFM tip apex. The localized surface plasmon resonance of the NDs is tailored to cover most of the visible-wavelength regime by controlling their size. The NTs show distinct polarization-dependent plasmon modes consistent with full-wave optical simulations. For the demonstration of the light-matter interaction control capability of NTIL nanostructures, we show that photoluminescence enhancement from MoS2 layers can be deliberately controlled by tuning the size of the nanostructures. Our results pave the way for the AFM-indentation-based fabrication of plasmonic nanostructures with a highly precise size and shape controllability and reproducibility.
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http://dx.doi.org/10.1039/d0nr08398dDOI Listing
March 2021

Giant nonlinear optical responses from photon-avalanching nanoparticles.

Nature 2021 01 13;589(7841):230-235. Epub 2021 Jan 13.

Department of Mechanical Engineering, Columbia University, New York, NY, USA.

Avalanche phenomena use steeply nonlinear dynamics to generate disproportionately large responses from small perturbations, and are found in a multitude of events and materials. Photon avalanching enables technologies such as optical phase-conjugate imaging, infrared quantum counting and efficient upconverted lasing. However, the photon-avalanching mechanism underlying these optical applications has been observed only in bulk materials and aggregates, limiting its utility and impact. Here we report the realization of photon avalanching at room temperature in single nanostructures-small, Tm-doped upconverting nanocrystals-and demonstrate their use in super-resolution imaging in near-infrared spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave lasers, and exhibit all of the defining features of photon avalanching, including clear excitation-power thresholds, exceptionally long rise time at threshold, and a dominant excited-state absorption that is more than 10,000 times larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of the pump intensity, owing to induced positive optical feedback in each nanocrystal. This enables the experimental realization of photon-avalanche single-beam super-resolution imaging with sub-70-nanometre spatial resolution, achieved by using only simple scanning confocal microscopy and without any computational analysis. Pairing their steep nonlinearity with existing super-resolution techniques and computational methods, ANPs enable imaging with higher resolution and at excitation intensities about 100 times lower than other probes. The low photon-avalanching threshold and excellent photostability of ANPs also suggest their utility in a diverse array of applications, including sub-wavelength imaging and optical and environmental sensing.
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http://dx.doi.org/10.1038/s41586-020-03092-9DOI Listing
January 2021

Nanorods with multidimensional optical information beyond the diffraction limit.

Nat Commun 2020 Nov 27;11(1):6047. Epub 2020 Nov 27.

Institute for Biomedical Materials & Devices (IBMD), Faculty of Science, University of Technology Sydney, Ultimo, NSW, 2007, Australia.

Precise design and fabrication of heterogeneous nanostructures will enable nanoscale devices to integrate multiple desirable functionalities. But due to the diffraction limit (~200 nm), the optical uniformity and diversity within the heterogeneous functional nanostructures are hardly controlled and characterized. Here, we report a set of heterogeneous nanorods; each optically active section has its unique nonlinear response to donut-shaped illumination, so that one can discern each section with super-resolution. To achieve this, we first realize an approach of highly controlled epitaxial growth and produce a range of heterogeneous structures. Each section along the nanorod structure displays tunable upconversion emissions, in four optical dimensions, including color, lifetime, excitation wavelength, and power dependency. Moreover, we demonstrate a 210 nm single nanorod as an extremely small polychromatic light source for the on-demand generation of RGB photonic emissions. This work benchmarks our ability toward the full control of sub-diffraction-limit optical diversities of single heterogeneous nanoparticles.
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http://dx.doi.org/10.1038/s41467-020-19952-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695702PMC
November 2020

Effectual Labeling of Natural Killer Cells with Upconverting Nanoparticles by Electroporation for In Vivo Tracking and Biodistribution Assessment.

ACS Appl Mater Interfaces 2020 Nov 13;12(44):49362-49370. Epub 2020 Oct 13.

Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Korea.

Natural killer (NK) cells, which are cytotoxic lymphocytes of the innate immune system and recognize cancer cells via various immune receptors, are promising agents in cell immunotherapy. To utilize NK cells as a therapeutic agent, their biodistribution and pharmacokinetics need to be evaluated following systemic administration. Therefore, in vivo imaging and tracking with efficient labeling and quantitative analysis of NK cells are required. However, the lack of the phagocytic capacity of NK cells makes it difficult to establish breakthroughs in cell labeling and subsequent in vivo studies. Herein, an effective labeling of upconverting nanoparticles (UCNPs) in NK cells is proposed using electroporation with high sensitivity and stability. The labeling performance of UCNPs functionalized with carboxy-polyethylene glycol (PEG) is better than with methoxy-PEG or with amine-PEG. The labeling efficiency becomes higher, but cell damage is greater as electric field increases; thus, there is an optimum electroporation condition for internalization of UCNPs into NK cells. The tracking and biodistribution imaging analyses of intravenously injected NK cells show that the labeled NK cells are initially distributed primarily in lungs and then spread to the liver and spleen. These advances will accelerate the application of NK cells as key components of immunotherapy against cancer.
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http://dx.doi.org/10.1021/acsami.0c12849DOI Listing
November 2020

Discrimination between target and non-target interactions on the viral surface by merging fluorescence emission into Rayleigh scattering.

Nanoscale 2020 Apr 13;12(14):7563-7571. Epub 2020 Mar 13.

Laboratory for Advanced Molecular Probing (LAMP), Bio Platform Technology Research Center, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeong-ro, Yuseong-gu, Daejeon 34114, South Korea.

Direct and quantitative determination of antibodies or cellular receptors dynamically binding to the surface of viral particles is the key issue for predicting the efficacy of therapeutic materials or host susceptibility to a new emerging pathogen. However, targeted visualization of infectious viruses is still highly challenging owing to their nanoscopic sizes and uncontrollable nonspecific interactions with loading molecules responsible for false signals. Here we present a multimodal single-molecule and single-particle (SMSP) visualization capable of simultaneously yet independently tracking Rayleigh scattering and fluorescence that, respectively, are generated from viruses (approximately 100 nm) and labeled interacting molecules. By analyzing real-time trajectories of fluorescent antibodies against a virus surface protein with reference to single virus-derived Rayleigh scattering, we determined heterogeneous binding stoichiometry of virus-antibody couplings irrespective of the nonspecific binder population. Therefore, our multimodal (or multi-level) SMSP assay visually identifies and selectively quantifies specific interactions between them with single binding event accuracy. As a 'specific-binding quantifier' to assess variable host susceptibility to a virus, it was further applied for distinguishing ratiometric bindings and spontaneous dissociation kinetics of synthesized isomeric receptors to influenza virus. The present framework could offer a solid analytical foundation for the development of a direct-acting antiviral agent inhibiting an integral viral enveloped protein and for nanobiological investigation for dissecting spatiotemporal nanoparticle-molecule interactions, which have been scarcely explored compared to those among plasmonic nanoparticles or among molecules only.
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http://dx.doi.org/10.1039/c9nr07415eDOI Listing
April 2020

SERS-based particle tracking and molecular imaging in live cells: toward the monitoring of intracellular dynamics.

Nanoscale 2019 Nov;11(45):21724-21727

Center for Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon 34114, South Korea.

Although diverse endogenous biomolecules involved in life processes are of major interest in cell biology, there is still a lack of suitable methods for studying biomolecules within live cells without labelling. Herein, we describe a near-infrared (NIR) surface-enhanced Raman scattering (SERS)-based particle tracking technique gathering chemical information inside live cells for monitoring their intracellular dynamics. The wide-field SERS imaging spectroscopy system facilitates high temporal resolution (200 ms) under high spatial resolution (512 × 512 pixels) for one live cell. With high spatiotemporal resolution and signal-to-background ratio, we show that the Raman signal from intracellular cargoes in live cells is sporadically observed and localized to a vesicular level.
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http://dx.doi.org/10.1039/c9nr05159gDOI Listing
November 2019

A smart tumor microenvironment responsive nanoplatform based on upconversion nanoparticles for efficient multimodal imaging guided therapy.

Biomater Sci 2019 Feb;7(3):951-962

Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin, 150001, P. R. China.

Near-infrared (NIR) light-induced imaging-guided cancer therapy has been studied extensively in recent years. Herein, we report a novel theranostic nanoplatform by modifying polyoxometalate (POM) nanoclusters onto mesoporous silica-coated upconversion nanoparticles (UCNPs), followed by loading doxorubicin (DOX) in the mesopores and coating a folate-chitosan shell onto the surface. In this nanoplatform, the core-shell structured UCNPs (NaYF4:Yb,[email protected]:Yb,Nd) showed special upconverting luminescence (UCL) when irradiated with high-penetration 808 nm NIR light, and the doped Yb and Nd ions endowed the sample with CT imaging properties, thus achieving a dual-mode imaging function. Moreover, the simultaneously generated heat mediated by the 808 nm NIR light may coordinate with the chemotherapy generated from the released DOX to realize an efficient synergistic therapy, verified by diverse in vitro and in vivo assays. The coated folate-chitosan shell can target the platform to tumor tissues when it was transported in the blood vessels and accumulated in tumor sites via the enhanced permeability and retention effect (EPR). Due to the acidic and reductive microenvironment of the tumor, the DOX released quickly with the dissolved folate-chitosan shell, exhibiting obvious tumor microenvironment (TME) responsive properties. The smart imaging-guided therapeutic nanoplatform should be highly promising in TME responsive therapy.
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http://dx.doi.org/10.1039/c8bm01243aDOI Listing
February 2019

Virus-mimetic polymer nanoparticles displaying hemagglutinin as an adjuvant-free influenza vaccine.

Biomaterials 2018 11 23;183:234-242. Epub 2018 Aug 23.

Department of Polymer Science and Engineering, Pusan National University, Busan, 46241, Republic of Korea. Electronic address:

The generation of virus-mimetic nanoparticles has received much attention in developing a new vaccine for overcoming the limitations of current vaccines. Thus, a method, encompassing most viral features for their size, hydrophobic domain and antigen display, would represent a meaningful direction for the vaccine development. In the present study, a polymer-templated protein nanoball with direction oriented hemagglutinin1 on its surface (H1-NB) was prepared as a new influenza vaccine, exhibiting most of the viral features. Moreover, the concentrations of antigen on the particle surface were controlled, and its effect on immunogenicity was estimated by in vivo studies. Finally, H1-NB efficiently promoted H1-specific immune activation and cross-protective activities, which consequently prevented H1N1 infections in mice.
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http://dx.doi.org/10.1016/j.biomaterials.2018.08.036DOI Listing
November 2018

Carboxymethyl dextran-based hypoxia-responsive nanoparticles for doxorubicin delivery.

Int J Biol Macromol 2018 Apr 11;110:399-405. Epub 2017 Nov 11.

Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul 06351, Republic of Korea; School of Chemical Engineering, College of Engineering, Sungkyunkwan University, Suwon 14619, Republic of Korea. Electronic address:

In an attempt to develop the hypoxia-responsive nanoparticles for cancer therapy, a polymer conjugate, consisting of carboxymethyl dextran (CMD) and black hole quencher 3 (BHQ3), was prepared. The polymer conjugate can self-assemble into nanoparticles (CMD-BHQ3 NPs) under aqueous conditions. The anticancer drug, doxorubicin (DOX), was loaded in CMD-BHQ3 NPs to prepare [email protected] NPs. The CMD-BHQ3 NPs released DOX in a sustained manner under physiological conditions, whereas the release rate of DOX remarkably increased under hypoxic conditions throughout the cleavage of the azo bond in BHQ3. In vitro cytotoxicity study revealed that [email protected] NPs showed higher toxicity under hypoxic conditions than normoxic conditions. Confocal microscopic images indicated oxygen-dependent intracellular release of DOX from [email protected] In vivo biodistribution study demonstrated that CMD-BHQ3 NPs were preferentially accumulated in the tumor after systemic administration into tumor-bearing mice. Overall, CMD-BHQ3 might be a promising carrier for selective drug release in the hypoxic tumor.
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http://dx.doi.org/10.1016/j.ijbiomac.2017.11.048DOI Listing
April 2018

Gold-stabilized carboxymethyl dextran nanoparticles for image-guided photodynamic therapy of cancer.

J Mater Chem B 2017 Sep 23;5(35):7319-7327. Epub 2017 Aug 23.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea.

Photodynamic therapy (PDT) has been extensively investigated to treat cancer since it induces cell death through the activation of photosensitizers by light. However, its success has been hampered by the insufficient selectivity of photosensitizers to tumor tissues. In an attempt to increase the therapeutic efficacy of PDT by targeting the photosensitizer specifically to the tumor site, we prepared chlorin e6 (Ce6)-loaded gold-stabilized carboxymethyl dextran nanoparticles (Ce6-GS-CNPs). Ce6-GS-CNPs possessed highly stable nanostructures and no significant change was observed in their particle size in the presence of serum for 6 days. When Ce6-GS-CNPs were intravenously injected into tumor-bearing mice, they exhibited prolonged circulation in the body and gradually accumulated in the tumor tissue. Under laser irradiation of the tumor site which could be recognized by the near-infrared fluorescence imaging system, Ce6-GS-CNPs effectively suppressed tumor growth. Overall, Ce6-GS-CNPs might have potential as nanomedicine for image-guided photodynamic cancer therapy.
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http://dx.doi.org/10.1039/c7tb01099kDOI Listing
September 2017

Convenient and effective ICGylation of magnetic nanoparticles for biomedical applications.

Sci Rep 2017 08 18;7(1):8831. Epub 2017 Aug 18.

Bioimaging Research Team, Korea Basic Science Institute, Cheongju, 28119, Korea.

Nanoprobes used for biomedical applications usually require surface modifications with amphiphilic surfactants or inorganic coating materials to enhance their biocompatibility. We proposed a facile synthetic approach for the phase transfer of hydrophobic magnetic nanoparticles by the direct adherence of fluorescent probes, without any chemical modifications, for use as a magnetic resonance (MR)/near-infrared (NIR) fluorescence bimodal imaging contrast agent. Indocyanine green (ICG) was used not only as an optical component for NIR imaging, but also as a surfactant for phase transfer with no superfluous moiety: we therefore called the process "ICGylation". Cell labeling and tracking in vivo with ICGylated magnetic nanoparticles were successfully performed by MR/NIR dual-mode imaging for three days, which showed remarkable biostability without any additional surface functionalization. We expect that this novel MR/NIR contrast agent demonstrating sensitive detection and simultaneous imaging capability can be used in diverse fields, such as the imaging and tracking of immune cells to confirm immunotherapeutic efficacy. The approach used could also be applied to other kinds of nanoparticles, and it would promote the development of advanced functional multimodal nanobioprobes.
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http://dx.doi.org/10.1038/s41598-017-09627-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5562755PMC
August 2017

Tuning 2D Light Upconversion Emission by Modulating Phonon Relaxation.

Chem Asian J 2017 Aug 26;12(16):2038-2043. Epub 2017 Jul 26.

Department of Chemistry, Kookmin University, 77, Jeongneung-ro, Seongbuk-gu, Seoul, 02707, Korea.

The photonic upconversion in rare earth atoms is widely used to convert "invisible" near infrared photons to "visible" photons with continuous wave light. By using a patterned substrate, upconversion become a route for creating new information-incorporating security codes. The amount of information in the cipher increases in proportion to the number of emission colors as well as the pattern structure. Subsequently, changing the chemical composition of upconversion phosphors on 2 D substrates is required to manufacture information-rich upconversion cryptography. In this study, we exploited temperature-controlled thermal reaction on upconversion films deposited on a quartz substrate to prepare security information codes. Multiple color emission was generated from upconversion films as the result of inserting high-frequency molecular oscillators into the film structures. Fourier-transform infrared (FTIR) and time-resolved study corroborated the mechanism of spectral variation of upconversion films.
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http://dx.doi.org/10.1002/asia.201700782DOI Listing
August 2017

Plasmonic Nanogap-Enhanced Raman Scattering with Nanoparticles.

Acc Chem Res 2016 12 8;49(12):2746-2755. Epub 2016 Nov 8.

Research Center for Convergence NanoRaman Technology (RC2NT), Korea Research Institute of Chemical Technology (KRICT) , DaeJeon 34114, South Korea.

Plasmonic coupling-based electromagnetic field localization and enhancement are becoming increasingly important in chemistry, nanoscience, materials science, physics, and engineering over the past decade, generating a number of new concepts and applications. Among the plasmonically coupled nanostructures, metal nanostructures with nanogaps have been of special interest due to their ultrastrong electromagnetic fields and controllable optical properties that can be useful for a variety of signal enhancements such as surface-enhanced Raman scattering (SERS). The Raman scattering process is highly inefficient, with a very small cross-section, and Raman signals are often poorly reproducible, meaning that very strong, controllable SERS is needed to obtain reliable Raman signals with metallic nanostructures and thus open up new avenues for a variety of Raman-based applications. More specifically, plasmonically coupled metallic nanostructures with ultrasmall (∼1 nm or smaller) nanogaps can generate very strong and tunable electromagnetic fields that can generate strong SERS signals from Raman dyes in the gap, and plasmonic nanogap-enhanced Raman scattering can be defined as Raman signal enhancement from plasmonic nanogap particles with ∼1 nm gaps. However, these promising nanostructures with extraordinarily strong optical signals have shown limited use for practical applications, largely due to the lack of design principles, high-yield synthetic strategies with nanometer-level structural control and reproducibility, and systematic, reliable single-molecule/single-particle-level studies on their optical properties. All these are extremely important challenges because even small changes (<1 nm) in the structure of the coupled plasmonic nanogaps can significantly affect the plasmon mode and signal intensity. In this Account, we examine and summarize recent breakthroughs and advances in plasmonic nanogap-enhanced Raman scattering with metal nanogap particles with respect to the design and synthesis of plasmonic nanogap structures, as well as ultrasensitive and quantitative Raman signal detection using these structures. The applications and prospects of plasmonic nanogap particle-based SERS are also discussed. In particular, reliable synthetic and measurement strategies for plasmonically coupled nanostructures with ∼1 nm gap, in which both the nanogap size and the position of a Raman-active molecule in the gap can be controlled with nanometer/sub-nanometer-level precision, can address important issues regarding the synthesis and optical properties of plasmonic nanostructures, including structural and signal reproducibility. Further, single-molecule/single-particle-level studies on the plasmonic properties of these nanogap structures revealed that these particles can generate ultrastrong, quantifiable Raman signals in a highly reproducible manner.
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http://dx.doi.org/10.1021/acs.accounts.6b00409DOI Listing
December 2016

White-light-emitting magnetite nanoparticle-polymer composites: photonic reactions of magnetic multi-granule nanoclusters as photothermal agents.

Nanoscale 2016 Oct;8(39):17136-17140

Department of Materials Science and Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea.

Magnetite nanoparticles combined with polymers produce white-light emission under multiphoton laser irradiation. Understanding the photonic reaction in magnetite-polymer composites is critical for application of magnetite NPs as photothermal agents. Laser irradiated magnetite nanoparticle-poly(methyl methacrylate) (PMMA) composites exhibit fluorescence due to the carbon double-bond formation resulting from the oxidation of the PMMA.
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http://dx.doi.org/10.1039/c6nr04408eDOI Listing
October 2016

Clear-cut observation of clearance of sustainable upconverting nanoparticles from lymphatic system of small living mice.

Sci Rep 2016 06 6;6:27407. Epub 2016 Jun 6.

Bioimaging Research Team, Korea Basic Science Institute, Cheongju 28119, Korea.

The significance of lymphatic system has gathered great attention for immunotechnology related to cancer metastasis and immunotherapy. To develop innovative immunodiagnostics and immunotherapy in in vivo environments, it is very important to understand excretion pathways and clearance of injected cargoes. Herein, we employed Tm(3+)-doped upconverting nanoparticles (UCNPs) with versatile advantages suitable for long-term non-invasive in vivo optical imaging and tracking. Transport and retention of the UCNPs in the lymphatic system were evaluated with high-quality NIR-to-NIR upconversion luminescence (UCL) imaging. We obtained their kinetic luminescence profiles for the injection site and sentinel lymph node (SLN) and observed luminescence signals for one month; we also examined UCL images in SLN tissues, organs, and faeces at each time point. We speculate that the injected UCNPs in a footpad of a small mouse are transported rapidly from the lymphatic system to the blood system and then eventually result in an efficient excretion by the hepatobiliary route. These results will support development of novel techniques for SLN biopsy as well as immunotechnology.
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http://dx.doi.org/10.1038/srep27407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4893699PMC
June 2016

Synthesis, Optical Properties, and Multiplexed Raman Bio-Imaging of Surface Roughness-Controlled Nanobridged Nanogap Particles.

Small 2016 Sep 29;12(34):4726-34. Epub 2016 Mar 29.

Department of Chemistry, Seoul National University, Seoul, 08826, South Korea.

Plasmonic nanostructures are widely studied and used because of their useful size, shape, composition and assembled structure-based plasmonic properties. It is, however, highly challenging to precisely design, reproducibly synthesize and reliably utilize plasmonic nanostructures with enhanced optical properties. Here, we devise a facile synthetic method to generate Au surface roughness-controlled nanobridged nanogap particles (Au-RNNPs) with ultrasmall (≈1 nm) interior gap and tunable surface roughness in a highly controllable manner. Importantly, we found that particle surface roughness can be associated with and enhance the electromagnetic field inside the interior gap, and stronger nanogap-enhanced Raman scattering (NERS) signals can be generated from particles by increasing particle surface roughness. The finite-element method-based calculation results support and are matched well with the experimental results and suggest one needs to consider particle shape, nanogap and nanobridges simultaneously to understand and control the optical properties of this type of nanostructures. Finally, the potential of multiplexed Raman detection and imaging with RNNPs and the high-speed, high-resolution Raman bio-imaging of Au-RNNPs inside cells with a wide-field Raman imaging setup with liquid crystal tunable filter are demonstrated. Our results provide strategies and principles in designing and synthesizing plasmonically enhanced nanostructures and show potential for detecting and imaging Raman nanoprobes in a highly specific, sensitive and multiplexed manner.
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http://dx.doi.org/10.1002/smll.201600289DOI Listing
September 2016

Nanoparticles based on quantum dots and a luminol derivative: implications for in vivo imaging of hydrogen peroxide by chemiluminescence resonance energy transfer.

Chem Commun (Camb) 2016 Mar;52(22):4132-5

Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Suwon 440-746, Republic of Korea. and Research Center for Convergence Nanobiotechnology (RC2NT), Korea Research Institute of Chemical Technology (KRICT), Daejeon 305-600, Republic of Korea. and School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.

Overproduction of hydrogen peroxide is involved in the pathogenesis of inflammatory diseases such as cancer and arthritis. To image hydrogen peroxide via chemiluminescence resonance energy transfer in the near-infrared wavelength range, we prepared quantum dots functionalized with a luminol derivative.
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http://dx.doi.org/10.1039/c5cc09850eDOI Listing
March 2016

Rapid Hepatobiliary Excretion of Micelle-Encapsulated/Radiolabeled Upconverting Nanoparticles as an Integrated Form.

Sci Rep 2015 10 23;5:15685. Epub 2015 Oct 23.

Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea.

In the field of nanomedicine, long term accumulation of nanoparticles (NPs) in the mononuclear phagocyte system (MPS) such as liver is the major hurdle in clinical translation. On the other hand, NPs could be excreted via hepatobiliary excretion pathway without overt tissue toxicity. Therefore, it is critical to develop NPs that show favorable excretion property. Herein, we demonstrated that micelle encapsulated (64)Cu-labeled upconverting nanoparticles (micelle encapsulated (64)Cu-NOTA-UCNPs) showed substantial hepatobiliary excretion by in vivo positron emission tomography (PET) and also upconversion luminescence imaging (ULI). Ex vivo biodistribution study reinforced the imaging results by showing clearance of 84% of initial hepatic uptake in 72 hours. Hepatobiliary excretion of the UCNPs was also verified by transmission electron microscopy (TEM) examination. Micelle encapsulated (64)Cu-NOTA-UCNPs could be an optimal bimodal imaging agent owing to quantifiability of (64)Cu, ability of in vivo/ex vivo ULI and good hepatobiliary excretion property.
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http://dx.doi.org/10.1038/srep15685DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4616227PMC
October 2015

Quantitative Plasmon Mode and Surface-Enhanced Raman Scattering Analyses of Strongly Coupled Plasmonic Nanotrimers with Diverse Geometries.

Nano Lett 2015 Jul 22;15(7):4628-36. Epub 2015 Jun 22.

†Laboratory for Advanced Molecular Probing (LAMP), Research Center for Convergence Nanobiotechnology, Korea Research Institute of Chemical Technology (KRICT), Daejeon 305-600, South Korea.

Here, we quantitatively monitored and analyzed the spectral redistributions of the coupled plasmonic modes of trimeric Au nanostructures with two ∼1 nm interparticle gaps and single-dye-labeled DNA in each gap as a function of varying trimer symmetries. Our precise Mie scattering measurement with the laser-scanning-assisted dark-field microscopy allows for individual visualization of the orientations of the radiation fields of the coupled plasmon modes of the trimers and analyzing the magnitude and direction of the surface-enhanced Raman scattering (SERS) signals from the individual plasmonic trimers. We found that the geometric transition from acute-angled trimer to linear trimer induces the red shift of the longitudinally polarized mode and the blue shift of the axially polarized mode. The finite element method (FEM) calculation results show the distinct "on" and "off" of the plasmonic modes at the two gaps of the trimer. Importantly, the single-molecule-level systematic correlation studies among the near-field, far-field, and surface-enhanced Raman scattering reveal that the SERS signals from the trimers are determined by the largely excited coupled plasmon between the two competing plasmon modes, longitudinal and axial modes. Further, the FEM calculation revealed that even 0.5 nm or smaller discrepancy in the sizes of two gaps of the linear trimer led to >10-fold difference in the SERS signal. Granted that two gap sizes are not likely to be completely the same in actual experiments, one of two gaps plays a more significant role in generating the SERS signal. Overall, this work provides the knowledge and handles for the understanding and systematic control of the magnitude and polarization direction of the both plasmonic response and SERS signal from trimeric nanostructures and sets up the platform for the optical properties and the applications of plasmonically coupled trimers and higher multimeric nanostructures.
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http://dx.doi.org/10.1021/acs.nanolett.5b01322DOI Listing
July 2015

The preferred upconversion pathway for the red emission of lanthanide-doped upconverting nanoparticles, NaYF4:Yb(3+),Er(3.).

Phys Chem Chem Phys 2015 May;17(20):13201-5

Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea.

Lanthanide-doped upconverting nanoparticles (UCNPs, NaYF4:Yb(3+),Er(3+)) are well known for emitting visible photons upon absorption of two or more near-infrared (NIR) photons through energy transfer from the sensitizer (Yb(3+)) to the activator (Er(3+)). Of the visible emission bands (two green and one red band), it has been suggested that the red emission results from two competing upconversion pathways where the non-radiative relaxation occurs after the second energy transfer (pathway A, (4)I15/2 → (4)I11/2 → (4)F7/2 → (2)H11/2 → (4)S3/2 → (4)F9/2 → (4)I15/2) or between the first and the second energy transfer (pathway B, (4)I15/2 → (4)I11/2 → (4)I13/2 → (4)F9/2 → (4)I15/2). However, there has been no clear evidence or thorough analysis of the partitioning between the two pathways. We examined the spectra, power dependence, and time profiles of UCNP emission at either 980 nm or 488 nm excitation, to address which pathway is preferred. It turned out that the pathway B is predominant for the red emission over a wide range of excitation powers.
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http://dx.doi.org/10.1039/c5cp01634gDOI Listing
May 2015

Bioreducible core-crosslinked hyaluronic acid micelle for targeted cancer therapy.

J Control Release 2015 Feb 27;200:158-66. Epub 2014 Dec 27.

School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea; Department of Health Sciences Technology, SAIHST, Sungkyunkwan University, Suwon 440-746, Republic of Korea; NanoBio Fusion Research Center, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea. Electronic address:

For drug delivery nanocarriers to be a safe and effective therapeutic option, blood stability, tumor-targetability, and intracellular drug release features should be considered. In this study, to develop a potent drug delivery carrier that can meet the multiple requirements, we engineered a bioreducible core-crosslinked polymeric micelle based on hyaluronic acid (CC-HAM) by a facile method using d,l-dithiothreitol in aqueous conditions. The CC-HAM exhibited enhanced structural stability under diluted conditions with PBS containing FBS or sodium dodecyl sulfates. We also successfully encapsulated doxorubicin (DOX), chosen as a hydrophobic anti-cancer drug, in CC-HAMs with high loading efficiency (>80%). The drug release rate of CC-HAMs was rapidly accelerated in the presence of glutathione, whereas the drug release was significantly retarded in physiological buffer (pH7.4). An in vivo biodistribution study demonstrated the superior tumor targetability of CC-HAMs to that of non-crosslinked HAMs, primarily ascribed to robust stability of CC-HAMs in the bloodstream. Notably, these results correspond with the improved pharmacokinetics and tumor accumulation of DOX-loaded CC-HAMs as well as their excellent therapeutic efficacy. Overall, these results suggest that the robust, bioreducible CC-HAM can be applied as a potent doxorubicin delivery carrier for targeted cancer therapy.
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http://dx.doi.org/10.1016/j.jconrel.2014.12.032DOI Listing
February 2015

Thiolated DNA-based chemistry and control in the structure and optical properties of plasmonic nanoparticles with ultrasmall interior nanogap.

J Am Chem Soc 2014 Oct 23;136(40):14052-9. Epub 2014 Sep 23.

Department of Chemistry, Seoul National University , Seoul 151-747, South Korea.

The design, synthesis and control of plasmonic nanostructures, especially with ultrasmall plasmonically coupled nanogap (∼1 nm or smaller), are of significant interest and importance in chemistry, nanoscience, materials science, optics and nanobiotechnology. Here, we studied and established the thiolated DNA-based synthetic principles and methods in forming and controlling Au core-nanogap-Au shell structures [Au-nanobridged nanogap particles (Au-NNPs)] with various interior nanogap and Au shell structures. We found that differences in the binding affinities and modes among four different bases to Au core, DNA sequence, DNA grafting density and chemical reagents alter Au shell growth mechanism and interior nanogap-forming process on thiolated DNA-modified Au core. Importantly, poly A or poly C sequence creates a wider interior nanogap with a smoother Au shell, while poly T sequence results in a narrower interstitial interior gap with rougher Au shell, and on the basis of the electromagnetic field calculation and experimental results, we unraveled the relationships between the width of the interior plasmonic nanogap, Au shell structure, electromagnetic field and surface-enhanced Raman scattering. These principles and findings shown in this paper offer the fundamental basis for the thiolated DNA-based chemistry in forming and controlling metal nanostructures with ∼1 nm plasmonic gap and insight in the optical properties of the plasmonic NNPs, and these plasmonic nanogap structures are useful as strong and controllable optical signal-generating nanoprobes.
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http://dx.doi.org/10.1021/ja504270dDOI Listing
October 2014

Hyaluronan nanoparticles bearing γ-secretase inhibitor: in vivo therapeutic effects on rheumatoid arthritis.

J Control Release 2014 Oct 7;192:295-300. Epub 2014 Aug 7.

Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Suwon 440-746, Republic of Korea; School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea; NanoBio Fusion Research Center, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea. Electronic address:

γ-Secretase inhibitors which prevent Notch activation are emerging as potent therapeutics for various inflammatory diseases, including ischemic stroke and rheumatoid arthritis. However, their indiscriminate distribution in the body causes serious side effects after systemic administration, since Notch proteins are ubiquitous receptors that play an important role in cellular functions such as differentiation, proliferation, and apoptosis. In this study, hyaluronan nanoparticles (HA-NPs) bearing a γ-secretase inhibitor (DAPT) were prepared as potential therapeutics for rheumatoid arthritis. In vivo biodistribution of the DAPT-loaded HA-NPs (DNPs), labeled with near-infrared dye, were observed using a non-invasive optical imaging system after systemic administration to a collagen-induced arthritis (CIA) mouse model. The results demonstrated that DNPs were effectively accumulated at the inflamed joint of the CIA mice. From the in vivo therapeutic efficacy tests, DNPs (1mg DAPT/kg) significantly attenuated the severity of RA induction compared to DAPT alone (2mg/kg), which was judged from clinical scores, tissue damage, and neutrophil infiltration. In addition, DNPs dramatically reduced the production of pro-inflammatory cytokines (TNF-α, IFN-γ, MCP-1, and IL-6, -12, -17) and collagen-specific auto-antibodies (IgG1 and IgG2a) in the serum of the CIA mice. These results suggest that DNPs have potential as therapeutics for rheumatoid arthritis.
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http://dx.doi.org/10.1016/j.jconrel.2014.07.057DOI Listing
October 2014

Upconverting nanoparticles: a versatile platform for wide-field two-photon microscopy and multi-modal in vivo imaging.

Chem Soc Rev 2015 Mar;44(6):1302-17

Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 151-742, Korea.

Lanthanide-doped upconverting nanoparticles (UCNPs) have recently attracted enormous attention in the field of biological imaging owing to their unique optical properties: (1) efficient upconversion photoluminescence, which is intense enough to be detected at the single-particle level with a (nonscanning) wide-field microscope setup equipped with a continuous wave (CW) near-infrared (NIR) laser (980 nm), and (2) resistance to photoblinking and photobleaching. Moreover, the use of NIR excitation minimizes adverse photoinduced effects such as cellular photodamage and the autofluorescence background. Finally, the cytotoxicity of UCNPs is much lower than that of other nanoparticle systems. All these advantages can be exploited simultaneously without any conflicts, which enables the establishment of a novel UCNP-based platform for wide-field two-photon microscopy. UCNPs are also useful for multimodal in vivo imaging because simple variations in the composition of the lattice atoms and dopant ions integrated into the particles can be easily implemented, yielding various distinct biomedical activities relevant to magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET). These multiple functions embedded in a single type of UCNPs play a crucial role in precise disease diagnosis. The application of UCNPs is extended to therapeutic fields such as photodynamic and photothermal cancer therapies through advanced surface conjugation schemes.
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http://dx.doi.org/10.1039/c4cs00173gDOI Listing
March 2015

Bioreducible carboxymethyl dextran nanoparticles for tumor-targeted drug delivery.

Adv Healthc Mater 2014 Nov 17;3(11):1829-38. Epub 2014 Apr 17.

School of Chemical Engineering, College of Engineering, Sungkyunkwan University, Suwon, 440-746, Republic of Korea.

Bioreducible carboxymethyl dextran (CMD) derivatives are synthesized by the chemical modification of CMD with lithocholic acid (LCA) through a disulfide linkage. The hydrophobic nature of LCA allows the conjugates (CMD-SS-LCAs) to form self-assembled nanoparticles in aqueous conditions. Depending on the degree of LCA substitution, the particle diameters range from 163 to 242 nm. Doxorubicin (DOX), chosen as a model anticancer drug, is effectively encapsulated into the nanoparticles with high loading efficiency (>70%). In vitro optical imaging tests reveal that the fluorescence signal of DOX quenched in the bioreducible nanoparticles is highly recovered in the presence of glutathione (GSH), a tripeptide capable of reducing disulfide bonds in the intracellular compartments. Bioreducible nanoparticles rapidly release DOX when they are incubated with 10 mm GSH, whereas the drug release is greatly retarded in physiological buffer (pH 7.4). DOX-loaded bioreducible nanoparticles exhibit higher toxicity to SCC7 cancer cells than DOX-loaded nanoparticles without the disulfide bond. Confocal laser scanning microscopy observation demonstrate that bioreducible nanoparticles can effectively deliver DOX into the nuclei of SCC7 cells. In vivo biodistribution study indicates that Cy5.5-labeled CMD-SS-LCAs selectively accumulate at tumor sites after systemic administration into tumor-bearing mice. Notably, DOX-loaded bioreducible nanoparticles exhibit higher antitumor efficacy than reduction-insensitive control nanoparticles. Overall, it is evident that bioreducible CMD-SS-LCA nanoparticles are useful as a drug carrier for cancer therapy.
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http://dx.doi.org/10.1002/adhm.201300691DOI Listing
November 2014

Time-gated pre-resonant femtosecond stimulated Raman spectroscopy of diethylthiatricarbocyanine iodide.

Phys Chem Chem Phys 2014 Mar;16(11):5312-8

Department of Bio & Nano Chemistry, Kookmin University, Seoul 136-702, Republic of Korea.

We present time-gated femtosecond stimulated Raman spectroscopy (fSRS) under the pre-resonance Raman conditions of diethylthiatricarbocyanine (DTTC) iodide. A 'pseudo emission-free' condition is achieved by delivering the probe beam ahead of the pump beam. Regeneratively amplified pulse trains are employed to create an angle-geometry (non-collimated) mixing between the pump and probe beams, leading to highly sensitive measurement of the stimulated Raman gain. Time-integrated spectroscopy allows for a more quantitative distinction between the contributions of stimulated Raman scattering and stimulated emission. We successfully obtain a highly sensitive (signal-to-noise ratio >100) stimulated Raman spectrum under the optimized conditions, which compares favourably to results obtained using two-dimensional correlation spectroscopy (2DCOS). Given the optical pre-resonance of ∼0.1 eV, the background signals mostly originate from the stimulated emission of excited electrons and are significantly reduced by partial overlapping of the pump and probe beams; a genuine fSRS spectral profile is obtained for a temporal delay of ∼0.2 ps between the two beams.
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http://dx.doi.org/10.1039/c3cp54870hDOI Listing
March 2014

Enhanced splicing correction effect by an oligo-aspartic acid-PNA conjugate and cationic carrier complexes.

J Control Release 2014 Feb 22;175:54-62. Epub 2013 Dec 22.

Department of Biochemistry, Chungnam National University, Daejeon 305-764, Republic of Korea. Electronic address:

Peptide nucleic acids (PNAs) are synthetic structural analogues of DNA and RNA. They recognize specific cellular nucleic acid sequences and form stable complexes with complementary DNA or RNA. Here, we designed an oligo-aspartic acid-PNA conjugate and showed its enhanced delivery into cells with high gene correction efficiency using conventional cationic carriers, such as polyethylenimine (PEI) and Lipofectamine 2000. The negatively charged oligo-aspartic acid-PNA (Asp(n)-PNA) formed complexes with PEI and Lipofectamine, and the resulting Asp(n)-PNA/PEI and Asp(n)-PNA/Lipofectamine complexes were introduced into cells. We observed significantly enhanced cellular uptake of Asp(n)-PNA by cationic carriers and detected an active splicing correction effect even at nanomolar concentrations. We found that the splicing correction efficiency of the complex depended on the kind of the cationic carriers and on the number of repeating aspartic acid units. By enhancing the cellular uptake efficiency of PNAs, these results may provide a novel platform technology of PNAs as bioactive substances for their biological and therapeutic applications.
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http://dx.doi.org/10.1016/j.jconrel.2013.12.015DOI Listing
February 2014

Hypoxia-responsive polymeric nanoparticles for tumor-targeted drug delivery.

Biomaterials 2014 Feb 26;35(5):1735-43. Epub 2013 Nov 26.

Department of Polymer Science and Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea; School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea; NanoBio Fusion Research Center, Korea Research Institute of Chemical Technology, Daejeon 305-600, Republic of Korea; Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Suwon 440-746, Republic of Korea. Electronic address:

Hypoxia is a condition found in various intractable diseases. Here, we report self-assembled nanoparticles which can selectively release the hydrophobic agents under hypoxic conditions. For the preparation of hypoxia-responsive nanoparticles (HR-NPs), a hydrophobically modified 2-nitroimidazole derivative was conjugated to the backbone of the carboxymethyl dextran (CM-Dex). Doxorubicin (DOX), a model drug, was effectively encapsulated into the HR-NPs. The HR-NPs released DOX in a sustained manner under the normoxic condition (physiological condition), whereas the drug release rate remarkably increased under the hypoxic condition. From in vitro cytotoxicity tests, it was found the DOX-loaded HR-NPs showed higher toxicity to hypoxic cells than to normoxic cells. Microscopic observation showed that the HR-NPs could effectively deliver DOX into SCC7 cells under hypoxic conditions. In vivo biodistribution study demonstrated that HR-NPs were selectively accumulated at the hypoxic tumor tissues. As consequence, drug-loaded HR-NPs exhibited high anti-tumor activity in vivo. Overall, the HR-NPs might have a potential as nanocarriers for drug delivery to treat hypoxia-associated diseases.
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http://dx.doi.org/10.1016/j.biomaterials.2013.11.022DOI Listing
February 2014

Single-molecule and single-particle-based correlation studies between localized surface plasmons of dimeric nanostructures with ~1 nm gap and surface-enhanced Raman scattering.

Nano Lett 2013 25;13(12):6113-21. Epub 2013 Nov 25.

Laboratory for Advanced Molecular Probing (LAMP), Research Center for Convergence Nanotechnology, Korea Research Institute of Chemical Technology , Daejeon 305-600, South Korea.

Understanding the detailed electromagnetic field distribution inside a plasmonically coupled nanostructure, especially for structures with ~ 1 nm plasmonic gap, is the fundamental basis for the control and use of the strong optical properties of plasmonic nanostructures. Using a multistep AFM tip-matching strategy that enables us to gain the optical spectra with the optimal signal-to-noise ratio as well as high reliability in correlation measurement between localized surface plasmon (LSP) and surface-enhanced Raman scattering (SERS), the coupled longitudinal dipolar and high-order multipolar LSPs were detected within a dimeric structure, where a single Raman dye is located via a single-DNA hybridization between two differently sized Au-Ag core-shell particles. On the basis of the characterization of each LSP component, the distinct phase differences, attributed to different quantities of the excited quadrupolar LSPs, between the transverse and longitudinal regimes were observed for the first time. By assessing the relative ratio of dipolar and quadrupolar LSPs, we found that these LSPs of the dimer with ~ 1 nm gap were simultaneously excited, and large longitudinal bonding dipolar LSP/longitudinal bonding quadrupolar LSP value is required to generate high SERS signal intensity. Interestingly, a minor population of the examined dimers exhibited strong SERS intensities along not only the dimer axis but also the direction that arises from the interaction between the coupled transverse dipolar and longitudinal bonding quadrupolar LSPs. Overall, our high-precision correlation measurement strategy with a plasmonic heterodimer with ~ 1 nm gap allows for the observation of the characteristic spectral features with the optimal signal-to-noise ratio and the subpopulation of plasmonic dimers with a distinct SERS behavior, hidden by a majority of dimer population, and the method and results can be useful in understanding the whole distribution of SERS enhancement factor values and designing plasmonic nanoantenna structures.
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http://dx.doi.org/10.1021/nl4034297DOI Listing
September 2014