Our research efforts are aimed at satisfying both in vivo and in vitro biological applications.
We achieve this by placing strong emphasis on understanding biomaterials surface science and applying the concepts of biosurface engineering in the development of our nanomaterials. Implantable neural prostheses and optical bioanalytical platforms represent the two main drivers for investigations in our lab.
Micro/nanoscale upconversion materials
Lanthanide trivalent ions (Ln3+) embedded in an inorganic host solid are capable of “upconversion”, which is the fascinating ability to convert multiple low-energy photons into a higher-energy photon. Micro/nanoscale upconversion materials gave birth to the promising applications, such as energy harvesting for solar cells, high-contrast bioimaging and deep tissue optogenetics.
We study the complex interaction between Ln3+ and host matrix to further improve the upconversion efficiency and to manipulate the upconversion emission spectrum exquisitely. We exploit several promising approaches, such like plasmonic local-field enhancement, light-matter interactions in optical cavities and breaking symmetry of host ions’ crystal-fields.
We struggle to realize the significant impact not only for scientific fields but also in real world applications by overcoming the intrinsic limitations of the conventional approaches. We believe that our findings will pave the ways of upconversion materials to the future technologies, such as anti-Stokes shift microlasers or all-photonic integrated circuit devices.
Systematic Investigation of the Wavelength-Dependent Upconversion Enhancement Induced by Single Plasmonic Nanoparticles. G Yi, DH Kim*, Journal of Physical Chemistry C 2018
Broadband Plasmonic Antenna Enhanced Upconversion and Its Application in Flexible Fingerprint Identification. W Xu, DH Kim*, Advanced Optical Materials 2018
Ultrafast Single-Band Upconversion Luminescence in a Liquid-Quenched Amorphous Matrix. BS Moon, DH Kim*, Advanced Materials 2018
Nanometric Manipulation of mesoscopic objects
Optical tweezers, which trap small objects like atoms, nanoparticles, DNA and cells in a highly focused optical field, can hold and move objects in three-dimensional space without a physical contact. We develop two-dimensional optical trapping systems to investigate novel phenomena of the systems and create new fields using the systems.
Raman spectroscopy of two-dimensional materials and biological samples.
We develop a Raman spectroscopy system combined Raman spectroscopy and optical tweezer to measure Raman scattering of two-dimensional materials or biological samples like exosomes and cells. The combined system would be high spatial resolution by overcoming the diffraction limit via near-field of trapped plasmonic nanoparticles and also enhance Raman intensities compared to conventional Raman spectroscopy.
Raman spectroscopy of two-dimensional materials and biological samples
Optical printing of plaasmonic nanoparticles
We push the limits of printing precision caused by the diffraction limit through the development of multi-wavelength optical tweezer systems. Optical printing of trapped plasmonic nanoparticles can be achieved by pushing the trapped nanoparticles to the substrates. We strive to enhance the printing precision to create unique and novel nanostructures and nanodevices with desired functions.
Optical Printing of Plasmonic Nanoparticles
In-situ preparation and evaluation of AgNPs- cored-shelled with environmental poly tannic acid for wound healing: In vitro study
Various metallic nanoparticles have been rapidly developed recently and used in many applications such as localized surface plasmon resonance (LSPR), sensors, medicine, electronics, and optics because of their unique chemical properties. Among those nanoparticles, silver nanoparticles (AgNPs) have been studied and analyzed extensively because of their exceptionally remarkable physical, chemical, and biological properties. AgNPs are known to possess such superiority which depends on their particle size, composition, and structure. Therefore, many strenuous efforts to develop AgNPs with the enhanced property for the designated application.
The AgNPs have a high tendency to undergo oxidation and aggregation because of their high surface energy, which suggests a need for enhancement of their colloidal stability with high concentration for their applicability in large scale in industry.
Herein, we attempted to prepare highly stable AgNP-core shell with high yield using environmental tannic acid as both reducing agent and capping agent with forming a core-shell layer around the surface of the AgNPs. The synthesized AgNPs were applied on the activated fiber for wound dressing application, to can help in the wound healing by killing the associated bacteria causing wound inflammation.
Synthesis of Core-Shell Silver Nanoparticles (Ag@PTA)
Schematic of Wound Dressing
TEM images of the prepared AgNPs capped with Tannic Acid
Bioanalytical platforms play an important role in health monitoring, early disease detection and disease prognostics. It is therefore crucial that these platforms have excellent sensitivity and selectivity.
At BSE lab, we develop biofunctionalized nanomaterials capable of detecting, from complex biological fluids, chemicals and biological molecules of interest with high levels of sensitivity and selectivity. We rely on localized surface plasmon resonance (LSPR) and surface-enhance Raman spectroscopy (SERS) for detection conducted both in solution as well as on solid substrates. Our plasmon-active materials range from single nanoparticles and nanoparticle dimers to long-range nanoparticle assemblies and hierarchical organic-inorganic nanocomposites. They are capable of translating molecular binding events to an optical signal that can even be visible via naked eye. Most notably, we have shown that the controlled formation of nanoparticle dimers in solution for the purpose of DNA sensing via LSPR-based colorimetry can tremendously improve the detection sensitivity by four orders of magnitude.
We continuously strive to formulate new strategies for convenient and direct detection without compromising our figures of merit. In relation, we are also committed to devise straightforward and cost-effective nanomaterial fabrication methodologies in the attainment of plasmonic sensing platforms. This will facilitate large-scale production at lower cost, which is relevant especially for point-of-care diagnostics.
Dark-field image of Au NanoRods and Plasmonic Detection Set-up
Distance-Mediated Plasmonic Dimers for Reusable Colorimetric Switches
: A Measurable Peak Shift of More than 60 nm. Guo L, Kim DH*, Small 2013
Oriented Gold Nanoparticle Aggregation for Colorimetric Sensors with Surprisingly High Analytical Figures of Merit for the detection of Vibrio cholera. Guo L, Kim DH*
Journal of the American Chemical Society 2013
A single-nanoparticle NO2 gas sensor constructed using active molecular plasmonics. Chen L, Kim DH*
Chemical Communications 2015
Tunable scattered colors over a wide spectrum from a single nanoparticle. Huang Y and Kim DH* Nanoscale 2012
Hierarchically structured one-dimensional TiO2 for protein immobilization, direct electrochemistry and mediator-free glucose sensing, Si P, Kim DH*
ACS Nano 2011
Immune-modulating surface coatings
to enhance long term performance of neural prostheses
We engineer surfaces that present immune-modulating biomolecules at molecular levels and exploit their functional effects on cellular behavior. This research is motivated by the realization that protein layers non-specifically adsorbed to the surface of implanted biomaterials differ substantially in composition and conformation from the proteins that comprise the extracellular matrix and the surfaces of cells. As a result, these non-specifically adsorbed layers both induce inflammation and lack the ligands that reduce inflammation.