Jiadong Li

Investigation of Halide-Induced Aggregation of Au Nanoparticles into Spongelike Gold

We present a facile method for fabricating spongelike Au structures by halide-induced aggregation and fusion of gold nanoparticles (AuNPs). Halide ions (F(-), Cl(-), Br(-), and I(-)) showed distinctly different effects on the synthesized AuNPs, which were characterized by localized surface plasmon resonance (LSPR) and dynamic light scattering measurements. A noticeable red-shift in the LSPR peak was found after Br(-) and I(-) ion treatment, which indicates the adsorption of halide atoms or ions on the AuNPs. The surface potential of AuNPs varied by treatment with different types of halides; this finding indicates that different halide ions have different effects on the AuNPs. Br(-) and I(-) ions showed strong affinity toward the AuNPs. The different affinities of halide ions toward the AuNPs play an important role in controlling the formation process of spongelike gold. Citrate ions adsorbed on AuNPs were displaced by halide ions to different extents. Such displacement determined the aggregation and fusion behaviors of the AuNPs and eventually the formation of different spongelike structures.

Detection of prostate-specific antigen with biomolecule-gated AlGaN/GaN high electron mobility transistors

In order to improve the sensitivity of AlGaN/GaN high electron mobility transistor (HEMT) biosensors, a simple biomolecule-gated AlGaN/GaN HEMT structure was designed and successfully fabricated for prostate specific antigen (PSA) detection. UV/ozone was used to oxidize the GaN surface and then a 3-aminopropyl trimethoxysilane (APTES) self-assembled monolayer was bound to the sensing region. This monolayer serves as a binding layer for attachment of the prostate specific antibody (anti-PSA). The biomolecule-gated AlGaN/GaN HEMT sensor shows a rapid and sensitive response when the target prostate-specific antigen in buffer solution was added to the antibody-immobilized sensing area. The current change showed a logarithm relationship against the PSA concentration from 0.1 pg/ml to 0.993 ng/ml. The sensitivity of 0.215% is determined for 0.1 pg/ml PSA solution. The above experimental result of the biomolecule-gated AlGaN/GaN HEMT biosensor suggested that this biosensor might be a useful tool for prostate cancer screening.

Ultrasensitive detection of Hg2+ using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg2+. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg2+ and thymines were combined. The current response of this Hg2+ ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg2+ ions on the surface by the highly specific thymine-Hg2+-thymine recognition. The dynamic linear range for Hg2+ detection has been determined in the concentrations from 10−14 to 10−8 M and a detection limit below 10−14 M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg2+ detection till now.

An AuNPs-functionalized AlGaN/GaN high electron mobility transistor sensor for ultrasensitive detection of TNT

Herein, an ultrasensitive sensor based on a AlGaN/GaN high electron mobility transistor (HEMT) was developed for the detection of 2,4,6-trinitrotoluene (TNT). The sensing surface of the AlGaN/GaN HEMT grid was covalently bonded with a layer of gold nanoparticles which were functionalized with cysteamine for specific electrostatic interaction with TNT. The binding of TNT to cysteamine through donor–acceptor interactions could affect the surface charge on the gate area of the AlGaN/GaN HEMT, resulting in a gate voltage change and density changes of the 2-dimensional electron gas (2EDG) at the interface of AlGaN/GaN. By the merit of the high electron mobility of the AlGaN/GaN transistor and robust binding between cysteamine and TNT, the sensor demonstrated a fast response and excellent performance with quantitative ranges at ppt levels (from 0.1 ppt to 10 ppb) with good selectivity towards TNT. This HEMT sensor showed attractive properties for TNT detection in terms of speed, sensitivity and miniaturization.

Enhanced thermoelectric performance of SnSe based composites with carbon black nanoinclusions

Recently, a single crystalline SnSe and its sodium doped compound are reported to have an ultralow thermal conductivity and a high thermoelectric figure of merit. However, the highest thermoelectric figure of merit for polycrystalline SnSe-based materials is not larger than 1. In this study, we report a high thermoelectric figure of merit 1.21 at 903 K for poly-crystalline SnSe, realized by incorporating a proper proportion of carbon black as nano-inclusions. The exceptional performance arises from the enhanced power factor, coming from an increased electrical conductivity at high temperatures.

Highly sensitive extended gate-AlGaN/GaN high electron mobility transistor for bioassay applications

Herein, an extended gate-AlGaN/GaN high electron mobility transistor (EG-AlGaN/GaN HEMT) with a high sensitivity for bioassay has been developed. The major difference between the EG-AlGaN/GaN HEMT transducer and a traditional AlGaN/GaN HEMT transducer is the sensing region. By extending the gate electrode and separating the sensing region from the channel of the AlGaN/GaN HEMT, our EG-AlGaN/GaN HEMT has a much larger sensing area and therefore achieves a low limit of detection (0.1 pg mL−1). Additionally, our transducer exhibits excellent linearity (R2 = 0.9934) with a wide range (from 0.1 pg mL−1 to 100 ng mL−1). We also demonstrate that the larger area of the extended sensing region can provide a larger current response of the transducer. The results give a proof-of-concept demonstration of the utilization of the EG-AlGaN/GaN HEMT for trace-level biological detection.