Welcome to Yong Il Park's Laboratory
"We develop well-designed functional nanomaterials
for the biomedical or energy device applications."
Our lab has open positions for graduate and undergraduate researchers.
기능성 나노재료 연구실에서 연구를 함께 수행할 대학원생 및 학부연구생을 모집합니다.
LATEST RESEARCH
We developed a facile and simple approach for the synthesis of alloy-based Sb nanoparticles embedded in a nitrogen-enriched carbon matrix (denoted as Sb@NC) through a straightforward chelation process. By incorporating NaCl as a sacrificial template, we successfully reduced the overall size of the carbon matrix, further mitigating volume change during charge–discharge process, and formed pores in the composite that facilitate the transport of sodium ions (denoted as s-Sb@NC). Through in-situ analyses, we determined the charge–discharge mechanism, and ex-situ cross-sectional imaging revealed the causes behind the decreased performance of commercial Sb and Sb@NC with the progress of the charge–discharge cycle.
We report increased rate capability and cycle stability achieved by introducing transition metal substitution and surface coating strategies. By substituting a portion of Ni and Mn with Cu and Mg (the sample name was denoted as NMCM), the P2–O2 transition which occurs at high voltages was alleviated. Additionally, a thin and uniform sodium phosphate coating layer suppressed surface side reactions occurring during charge–discharge processes, as observed through ex-situ X-ray photoelectron spectroscopy and ex-situ transmission electron microscopy. Compared to the pristine sample, the capacity improved by 48% at a high current density of 4 A g–1. After 100 cycles, the sodium-phosphate-coated sample (NMCM@P) retained about 90% of its capacity, whereas NMCM had a capacity retention of 63%. When evaluating the longer stability of SIC full cells, NMCM@P exhibited an outstanding stability of 71% after 5000 cycles. This was higher than that of NMCM, which retained only 17% of its initial capacity.
This study proposes encapsulating Ni2P with carbon nanofibers (Ni2P@CNF) using a simple electrospinning method to produce an anode material suitable for high-performance SIHCs. The three-dimensional (3D) network of CNF interconnections delivers improved electrical conductivity and ion diffusivity. The CNF can efficiently reduce the stress repeatedly inflicted on the Ni2P because of the volume change, leading to superior stability. In the half cell, the Ni2P@CNF reveals a high specific capacity of 184 mAh g−1 than Ni2P (40 mAh g−1) and Ni2P/CNF (92 mAh g−1) at a current density of 0.1 A g−1. The Ni2P@CNF possesses a high-rate capability of 81 mAh g−1 at a current density of 2 A g−1. Furthermore, the ion diffusivity and electrochemical properties were investigated using electrochemical impedance spectroscopy. By integrating the Ni2P@CNF anode with an activated carbon (AC) cathode, the SIHC exhibits a high energy density of 136 Wh kg−1 and a high power density of 16.3 kW kg−1. The fabricated SIHC demonstrates high long-term stability with a capacity retention of 80% over 3,500 cycles.
One-pot hydrothermal method is adopted for novel in situ preparation of upconversion nanoparticles (UCNPs)@Au composites using a binary functional EDTA salt, which is employed as a surfactant and reducing agent. The composites are electrostatically conjugated with metal-coordinated Prussian blue (PB) to yield UCNP@Au+PB nanocomposites (NCs), which demonstrated 21-fold upconversion emission quenching by FRET compared to UCNPs. Additionally, the PB, UCNP@Au, and NCs demonstrated synergistically reduced trap (α ~0.85) and enhanced ultrasensitive broadband (432 nm to 980 nm) photodetection. The NCs-based gate-free epitaxial graphene device demonstrated excellent high photoresponsivity (5.9 × 105 AW-1), detectivity (2.17 × 1014 ), and normalized gain (2.06 × 10−4 m2V-1) at 318 nWcm-2 (532 nm) and a bias voltage of 1 V. The Au plasmons enhanced the one-photon-enabled visible absorption of Er3+ ions, and PB exhibited broad absorption and enhanced the carrier density of the device, resulting in an ultrahigh photoresponse. The obtained device performance is the highest to date among their class of nanohybrids. Also, these NCs can readily detect polychromatic light and signals from daily-use appliances, indicating their potential for applications in consumer electronics.
We engineered lanthanide-doped core-shell and core-shell-shell NCs using the thermal decomposition method. These core-shell NCs exhibit blue and green emissions from Er/Tm ions when sensitized by Yb ions under 980 nm laser irradiation. Similar emissions are observed from core-shell-shell NCs, where Yb and Nd ions sensitize emissions under 980 and 800 nm excitations, respectively. We improved the upconversion luminescence efficiency by introducing an active inert layer as a shell on the core and core-shell NCs. This active inert layer, doped with Eu/Tb ions, acts as a protective layer, enhancing radiant efficiency by mitigating defects on the NC surface. Moreover, we functionalized the NC surface with 2,6-PDA ligands using the hydrothermal method, enabling excitation of the NCs under UV light irradiation. Upon 282 nm excitation, strong red/green emissions are observed from Eu/Tb ions via 2,6-PDA ligand sensitization.
We have successfully developed a rational and effective method for detecting glyphosate concentrations in the nanomolar range through luminescence enhancement. For this purpose, we synthesized NH2-MIL-88B (Fe) MOF NCs. The MOF NCs contain coordinative ligands and metal clusters. The Fe clusters act as luminescence quenchers, suppressing emission from the MOF due to photoinduced electron transfer from the ligand to Fe3+ ions. The phosphate group of glyphosate competes with the carboxylate of the ligand in the MOF. As a result, the coordination between ligand molecules and Fe metal clusters in the MOF weakens, causing the ligand molecules to separate from the Fe cluster. This process diminishes the PET and regenerates the ligand emission at 450 nm. The luminescence enhancement exhibits high selectivity toward glyphosate and shows minimal interference from various pesticides and metal ions. The limit of detection was calculated as 198 nM, and the performance of the detection probe was evaluated in drinking water.
This study reports a NaTi2(PO4)3/MXene (NTP/MXene) composite as a battery-type anode material for high-performance SICs. The NTP/MXene composite is synthesized via the in situ growth of NTP, with poor electrical conductivity, on the surface of MXene, with a two-dimensional structure and high electrical conductivity. The in situ synthesized NTP/MXene composite exhibits better rate performance and cyclic stability than NTP or MXene. These improved electrochemical properties are attributed to the synergistic effect of the pseudocapacitive characteristics of MXene and the battery characteristics of NTP. An SIC assembled with the NTP/MXene composite and activated carbon affords a high energy density of 112.1 Wh kg−1 and a high power density of 9.5 kW kg−1. Furthermore, it exhibits excellent long-term capacity retention of 78% even after 10000 cycles.
The key to increasing photocatalytic activity is to maximize solar spectrum utilization and minimize the recombination of photosynthetic carriers. Along with ZnFe2O4 for visible light absorption, we designed a novel heterojunction photoelectrode using upconversion nanoparticles (UCNPs) with near-infrared (NIR) light absorption to improve solar absorption efficiency. The UCNP-ZFO/TiO2 exhibited a significantly higher photocurrent density of 0.795 mA cm-2 compared to that of the pristine TiO2 (0.260 mA cm-2). The applied bias photon-to-current efficiency of UCNP-ZFO/TiO2 was 4.1 times higher than that of TiO2, and its photoanode had the lowest charge transfer resistance and highest charge density among the prepared photoelectrodes. This implies that the combination of UCNPs and ZFO on the TiO2 photoanode can be an effective strategy to significantly improve photoelectrochemical performance owing to the synergetic utilization of NIR light by UCNPs and that of visible light by the ZFO nanoparticles.
