Interaction with electron donor and acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.

Changes in the electronic structure and properties of graphene induced by molecular charge-transfer

Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-005031.pdf

Black Phosphorus Field-effect Transistors

WSe2 2D p-type semiconductor-based electronic devices for information technology: Design, preparation, and applications

Exosomal miRNA is an ideal source of noninvasive biomarker for the diagnosis of cancer. Sensitive and accurate analysis of exosomal miRNA plays an important role in facilitating clinical applications. Herein, we have developed a novel electrochemical method for exosomal miRNA assay coupling strand displacement amplification (SDA) and dumbbell hybridization chain reaction (DHCR). The target triggered isothermal SDA process generates a large number of single-stranded DNA products to assist the formation of the three-way junction structure on the electrode surface. In addition, dumbbell DNA fuel strands (DHP1 and DHP2) are designed for the hybridization chain reaction. This novel form of HCR produces DNA nanostructures with a tight conformation, which facilitates the enhancement of the electrochemical response. The combination of the dual signal amplification significantly improves the sensitivity for the exosomal miRNA assay, resulting in a limit of detection (LOD) as low as 7.3 aM. More importantly, the method is successfully applied in the analysis of cells and human serum samples, which demonstrates the potential utility in point-of-care testing (POCT) applications.

Dumbbell Hybridization Chain Reaction Based Electrochemical Biosensor for Ultrasensitive Detection of Exosomal miRNA.

Synthesis of Wafer-Scale Graphene with Chemical Vapor Deposition for Electronic Device Applications

A flexible graphene field-effect transistor (Gr-FET) biosensor for ultrasensitive and specific detection of miRNA without labeling and functionalization is reported. The flexible biosensor presents...

Ultrasensitive Label-free MiRNA Sensing Based on a Flexible Graphene Field-Effect Transistor without Functionalization

Non-invasive early diagnosis is of great significance in disease pathologic development and subsequent medical treatments, and microRNA (miRNA) detection has attracted critical attention in early cancer screening and diagnosis. High-throughput, sensitive, economic, and fast miRNA sensing platforms are necessary to realize the low-concentration miRNA detection in clinical diagnosis and biological studies. Here, we developed an attomolar-level ultrasensitive, rapid, and multiple-miRNA simultaneous detection platform enabled by nanomaterial locally assembled microfluidic biochips. This platform presents a large linear detection regime of 1 aM-10 nM, an ultralow detection limit of 0.146 aM with no amplification, a short detection time of 35 min with multiplex miRNA sensing capability, and a small sample volume consumption of 2 μL. The detection results of five miRNAs in real samples from breast cancer patients and healthy humans indicate its excellent capacity for practical applications in early cancer diagnosis. The proposed ultrasensitive, rapid, and multiple-miRNA detection microfluidic biochip platform is a universal miRNA detection approach and an important and valuable tool in early cancer screening and diagnosis as well as biological studies.

Attomolar-Level Ultrasensitive and Multiplex microRNA Detection Enabled by a Nanomaterial Locally Assembled Microfluidic Biochip for Cancer Diagnosis.

Lead (Pb2+) is the most common toxic heavy metal ion in the natural environment and causes enormous harm to public health for its non-metabolic accumulation. Therefore, it is essential to develop sensitive and robust system for detecting lead ions. Here, we provide a dual-enhancement (DE) surface-enhanced Raman scattering (SERS) strategy, that integrate the chemical enhancement of monolayer graphene and the electromagnetic enhancement of hybrid metal nanostructure, for sensitive quantitative detection of Pb2+ through enzyme-linked reaction principle. The enhancement factor (EF) of 3.85 × 108 of the DE SERS substrate was achieved. Pb2+ ions in water can be detected quantitatively through recording the Raman signal intensity of the Cy3. The results show that the developed SERS sensor owns a wide dynamic response range between 10 pM and 100 nM with a detection limit of 4.31 pM for Pb2+ detection. Furthermore, this high-quality SERS sensor possesses high Pb2+ specificity and can be recycled at least three times. In addition, the sensing mechanism of the SERS sensor is discussed and validated by the experiments and finite-difference time-domain (FDTD) simulations. The proposed dual-enhancement, reusable SERS sensor provides an effective approach for heavy ion detection and gene analysis in the field of environmental and life science and technology.

Reusable dual-enhancement SERS sensor based on graphene and hybrid nanostructures for ultrasensitive lead (II) detection

Saxitoxin (STX) is one of the most important marine toxins which affects the safety of domestic water. Rapid, sensitive and selective recognition of STX is crucial in environment monitoring. Here, we demonstrate a facile and ultrasensitive colorimetric sensor based on gold nanoparticles (Au NPs) and aptamer (Au NPs-aptamer biosensor) for specific and quantitative detection of STX. The aptamer reacts specifically with STX, resulting in the aggregation of Au NPs and the color change of the Au NP solution. The lowest detection concentration of the colorimetric sensor is 10 fM (3 fg mL−1), and a good linear relationship (R2 = 0.9852) between the absorbance ratio and STX concentrations (10 fM to 0.1 μM) indicates that our Au NPs-aptamer biosensor can be used for quantitative sensing of STX. The detection time of STX is 30 minutes, and the sensor is successfully applied in the specific detection of STX in seawater. The Au NP-aptamer biosensor shows great potential in practical applications to monitor environmental pollution, marine aquaculture pollution, and seafood safety.

/pdf/a-rapid-and-ultrasensitive-colorimetric-biosensor-based-on-1l1jqg68dc.pdf

Yakun Gao

Papers

Ultrasensitive Label-free MiRNA Sensing Based on a Flexible Graphene Field-Effect Transistor without Functionalization

Attomolar-Level Ultrasensitive and Multiplex microRNA Detection Enabled by a Nanomaterial Locally Assembled Microfluidic Biochip for Cancer Diagnosis.

Reusable dual-enhancement SERS sensor based on graphene and hybrid nanostructures for ultrasensitive lead (II) detection

A rapid and ultrasensitive colorimetric biosensor based on aptamer functionalized Au nanoparticles for detection of saxitoxin

Rapid and sensitive triple-mode detection of causative SARS-CoV-2 virus specific genes through interaction between genes and nanoparticles.