Hunsang Jung

Organic memory device with polyaniline nanoparticles embedded as charging elements

Polyaniline nanoparticles (PANI NPs) were synthesized and fabricated as charging elements for organic memory devices. The PANI NPs charging layer was self-assembled by epoxy-amine bonds between 3-glycidylpropyl trimethoxysilane functionalized dielectrics and PANI NPs. A memory window of 5.8 V (ΔVFB) represented by capacitance-voltage hysteresis was obtained for metal-pentacene-insulator-silicon capacitor. In addition, program/erase operations controlled by gate bias (−/+90 V) were demonstrated in the PANI NPs embedded pentacene thin film transistor device with polyvinylalcohol dielectric on flexible polyimide substrate. These results can be extended to development of fully organic-based electronic device.

Robust ZnO nanoparticle embedded memory device using vancomycin conjugate and its biorecognition for electrical charging node

Conjugation of antibiotic vancomycin (VAN) on nanoparticles (NPs) has recently initiated novel works in the nanobiotechnology field. In this study, a bioelectronic structure using VAN conjugated zinc oxide (ZnO) NPs as charge storing elements on metal-pentacene-insulator-silicon (MPIS) device is demonstrated. Highly specific molecular recognition between the VAN and membrane protein unit mimicked from VAN-resistant bacteria is employed as the formation mechanism of self-assembly monolayers (SAMs) of ZnO NPs. The insulator surface is modified with the VAN cognate peptide of L-Ala-D-Glu-L-Lys-D-Ala-D-Ala by chemical activator coupling. Hysteretic behaviors in capacitance versus voltage (C-V) curves are obtained for the charged ZnO NPs exhibiting flatband voltage shifts, which demonstrate the charge storage on the VAN conjugated ZnO NPs. The potential perspective of this study will be a tangible progress of biomolecular electronics implemented by the interface between biomolecules and electronics.

Organic memory device with self-assembly monolayered aptamer conjugated nanoparticles

An organic memory structure using monolayered aptamer conjugated gold nanoparticles (Au NPs) as charge storage nodes was demonstrated. Metal-pentacene-insulator-semiconductor device was adopted for the non-volatile memory effect through self assembly monolayer of A10-aptamer conjugated Au NPs, which was formed on functionalized insulator surface with prostate-specific membrane antigen protein. The capacitance versus voltage (C-V) curves obtained for the monolayered Au NPs capacitor exhibited substantial flat-band voltage shift (ΔVFB) or memory window of 3.76 V under (+/-)7 V voltage sweep. The memory device format can be potentially expanded to a highly specific capacitive sensor for the aptamer-specific biomolecule detection.

Electrical charging characteristics of Au NPs embedded by sequence specific complementary DNA hybridization in metal-pentacene-insulator-silicon device

It was demonstrated that an organic device structure using self-assembly monolayers (SAMs) gold nanoparticles (Au NPs) formed by complementary hybridization between probe DNA and target DNA. The device was fabricated in a form of metal-pentacene-insulator-silicon capacitor. Dielectric SiO2 layer was modified with 3-glycidylpropyl-trimethoxysilane (GPTMS) for SAMs formation of amine terminated probe oligo-DNA. The Au NPs conjugated by thiol terminated target oligo-DNA were charging elements, which were complementarily hybridized on the probe DNA SAMs. Capacitance versus voltage (C-V) curves exhibited flatband voltage shifts, which demonstrated the presence of charging effect. Charging behavior showed volatile effect which potentially was targeted to sensor application and utilization of DNA as material for biomolecule-based electronic device.

Affinity characteristic of terminal sequence in vancomycin resistant Enterococcus (VRE) membrane peptides on nanobiosensor chip using localized surface plasmon resonance

In this study, specific binding affinity between vancomycin (VAN) conjugated 40-50 nm gold nanoparticles (Au NPs) implemented on a sensor chip and pentapeptide mimicking pathogenic VAN resistant Enterococcus (VRE) wall membrane was employed as nanosensor format based on localized surface plasmon resonance (LSPR). Two pentapeptides, which were also anchored to 5 nm Au NPs, having two different terminal sequences of d-Ala-d-Ala and d-Ala-d-Lac respectively were compared in specific binding affinity toward the VAN conjugated nanosensor. Binding affinity difference identified by the LSPR characteristic in the nanosensor was shown in absorbance intensity and absorption wavelength shift between the two different terminal pentapeptides. The absorbance intensity clearly indicated that the pentapeptide having terminal d-Ala-d-Lac showed less affinity toward VAN conjugated nanosensor chip than that having terminal d-Ala-d-Ala. It indicates that the VRE itself has relatively weak binding strength towards the VAN, which may be used as a probe molecule for the VRE. Therefore, in order to design a VRE sensor using the VAN affinity, an indirect LSPR method can be devised instead of direct LSPR method.

Direct immune-detection of cortisol by chemiresistor graphene oxide sensor

In this study, a biosensor to detect a stress biomarker of cortisol using cortisol monoclonal antibody (c-Mab) covalently immobilized on reduced graphene oxide (rGO) channel as electrical sensing element was demonstrated. Highly specific immune-recognition between the c-Mab and the cortisol was identified and characterized on a basis of resistance change at the rGO channel based chemiresistor sensor achieving the limit of detection of 10pg/mL (27.6 pM). In addition, cortisol concentrations of real human salivary sample and buffer solution of rat adrenal gland acute slices, which could secret the cortisol induced by adrenocorticotropic hormone (ACTH), were directly measured by the chemiresistor corresponding to the specific sensing of the cortisol. The rGO chemiresistor could selectively measure the cortisol levels in spite of diverse neuroendocrines existence. The potential perspective of this study can be a protocol of new cortisol sensor development, which will be applicable to point-of-care testing (POCT) targeted for salivary cortisol, in vitro psychobiological study on cortisol induction, and implantable sensor chip in the future.

Surface Plasmon Resonance Characteristics of Au Nanoparticles Layered Sensor Chip for Direct Detection of Stress Hormone Conjugated by Nanoparticles

In this study, localized surface plasmon resonance (LSPR) effect was characterized for immuneassay to detect cortisol conjugated nanoparticles (NPs) using a cuvette-compatible Au NPs layered sensor chip. A neuro stress hormone, cortisol, as target molecule was conjugated to 2 nm, 5 nm, 30 nm, and 40 nm Au NPs or 14 nm zinc oxide (ZnO) NPs to enhance the LSPR detection signals as plasmonic coupling elements with respect to cortisol monoclonal antibody (c-Mab) of probe molecule, which was immobilized on the Au NPs layered sensor. The cortisol conjugated 2 nm and 5 nm Au NPs and 14 nm ZnO NPs, which were selectively immune- bound to the c-Mab coated Au NPs sensor, showed LSPR effects to induce absorbance increases under UV-Vis spectroscopy. Also, the cortisol conjugated 2 nm, 5 nm, 30 nm and 40 nm Au NPs could show disparate plasmonic coupling effects to shift maximum absorbance wavelength peaks. Even though the cortisol conjugated 14 nm ZnO NPs could show increased absorbance only, the conjugation of cortisol to both Au and ZnO NPs was proved to enhance direct LSPR detection of the cortisol, which could not be explicitly sensed by itself for direct LSPR signal.