[Show abstract][Hide abstract] ABSTRACT: The discontinuous Vertical Evaporation-driven Colloidal Deposition (dVECD) method has been used as a green technique for formatting nanoparticle wires by the direct deposition of nanoparticles from colloid suspensions onto hydrophilic substrates, without any lithographic procedures. Gold nanoparticles of different sizes are deposited into wire arrays for electronic detection of biological molecules. A sensitive detection of DNA molecules as low as ∼1 pM is achieved due to a high surface to volume ratio of the porous structures. The effects of the gold nanoparticles' size, DNA concentration, and DNA length on detection sensitivity of these gold nanoparticle wire sensors are discussed. Moreover, we can also detect the interaction between DNAs and proteins. Gold nanoparticle wires prepared by the nontoxic and simple dVECD are promising for detecting viruses involved in diseases.
[Show abstract][Hide abstract] ABSTRACT: The effect of applied pressure on event duration distributions in 3 kb dsDNA translocation is systematically investigated. The effects of pressure magnitude and nanopore size on the length discrimination between 615 bp and 1.14 kbp dsDNA is studied. The pressure-controlled DNA translocation in solid-state nanopores makes a significant contribution to improve the temporal resolution in DNA single-molecule detection.
[Show abstract][Hide abstract] ABSTRACT: The first electronic measurement of DNA translocation through ultrathin BN nanopores is demonstrated. BN nanopores show much higher detection sensitivity compared with SiN nanopores. BN has as high a spatial resolution as graphene. The ultrathin BN nanopores provide substantial opportunities in realizing high-spatial-sensitivity nanopore electrical devices for various applications.
[Show abstract][Hide abstract] ABSTRACT: Building bridges: Molecular functionalities can be installed into electronic devices having graphene-molecule junctions generated by the dash-line lithographic (DLL) method. When a sulfonic acid modified azobenzene unit served as the bridge, the conductance could be switched reversibly by irradiation with light of different wavelengths and by exposure to solutions of different pH. Other molecular transport junctions were generated by metal ion coordination.
Angewandte Chemie International Edition 03/2013; · 13.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Quasi-one-dimensional electroactive materials with zigzag shape are fabricated by supramolecular self-assembly of a tetrathiafulvalene (TTF) derivative and metal ions under mild conditions. This is the first time that self-assembled organic conductors with zigzag shape are reported.
Chemical Communications 12/2012; · 6.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A molecular-scale gap array is introduced into a single-layer graphene sheet by a lithographic dash-line cutting process. Electrically active molecules are then covalently wired into these point contacts in high yield, thus forming stable molecular devices that for example are able to reversibly switch their conductance by chemical treatment.
Angewandte Chemie International Edition 11/2012; · 13.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbon nanomaterials field-effect transistor (FET)-based electrical biosensors provide significant advantages over the current gold standards, holding great potential for realizing direct, label-free, real-time electrical detection of biomolecules in a multiplexed manner with ultrahigh sensitivity and excellent selectivity. The feasibility of integrating them with current complementary metal oxide semiconductor platform and a fluid handling module using standard microfabrication technology opens up new opportunities for the development of low-cost, low-noise, portable electrical biosensors for use in practical future devices. In this article, we review recent progress in the rapidly developing area of biomolecular interaction detection using FET-based biosensors based on the carbon nanomaterials single-walled carbon nanotubes (SWNTs) and graphene. Detection scenarios include DNA–DNA hybridization, DNA–protein interaction, protein function and cellular activity. In particular, we will highlight an amazing property of SWNT- or graphene-FETs in biosensing: their ability to detect biomolecules at the single-molecule level or at the single-cell level. This is due to the size comparability and the surface compatibility of the carbon nanomaterials with biological molecules. We also summarize some current challenges the scientific community is facing, including device-to-device heterogeneity and the lack of system integration for uniform device array mass production.
[Show abstract][Hide abstract] ABSTRACT: The stability and surface evolution of solid-state nanopores in aqueous solutions are extremely important since they would get immersed in solutions during DNA translocation experiment for DNA analyses. In this work, we systematically studied the size evolution of SiN nanopores in ethanol, deionized water and potassium chloride (KCl) solutions by careful surface characterization and composition analyses using a transmission electron microscope. Surprisingly, we found that nanopores closed up completely in ethanol in an hour and showed a 30% and 20% size decrease in deionized water and KCl solutions, respectively. Strong evidence of surface oxidation was found by composition analyses in the nanopore area. Nanopore size evolution was strongly dependent on initial pore size and solution pH value. In pH = 13 KCl solution, SiN nanopores were observed to increase in size instead of decrease. The results not only provide useful information for DNA detection based on solid-state nanopores, but can also guide design and application of other nanodevices exposed to electrolyte-solvent systems such as cell-on-a-chip devices and biosensors.
[Show abstract][Hide abstract] ABSTRACT: A poly(methyl methacrylate) assisted dry transfer method was developed to transfer graphene microflake onto a suspended SiN chip in an effective and efficient way for further graphene nanopore drilling for DNA analysis. Graphene microflakes can be patterned by e-beam lithography to a designed shape and size on a large scale of a few thousands simultaneously. Subsequently, individual graphene microflakes can be picked up and transferred to a target hole on a suspended SiN membrane with 1 µm precision via a site-specific transfer-printing method. Nanopores with different diameters from 3 to 20 nm were drilled on the as-transferred graphene membrane in a transmission electron microscope. This method offers a fast and controllable way to fabricate graphene nanopores for DNA analyses.
[Show abstract][Hide abstract] ABSTRACT: We detail a facile fabrication and testing method of functionalizing single-layer graphenes (SLGs) by photoactive TiO2 thin films as test-beds for building efficient multifunctional optoelectronic devices. Interestingly, tuning the photoactivity of TiO2 enables us to realize fast and significant photoswitching effects in TiO2-graphene devices. More importantly, using the hybrid devices as solid-state gas sensors, we have demonstrated a reversible and linear electrical sensitivity towards oxygen gas in the full concentration range (5–100%) at room temperature and ambient pressure, with a calculated minimum detection limit (MDL) of 0.01% oxygen. The unique oxygen sensitivity of the devices is attributed to the synergetic effect of the photoactivity of TiO2 and the environmental ultrasensitivity of SLGs. These results form the basis for new types of future ultrasensitive multifunctional integrated devices for a variety of possible detection and/or sensing applications.
Chemical Science 08/2011; 2(9):1860-1864. · 8.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Solution-processed photodetectors with high sensitivity over a broad spectral range are highly desirable for low-cost, large-area sensing applications in both industrial and scientific communities. In general, the detector sensitivities are limited by inefficient carrier dissociation and transport of materials and high contact Schottky barriers. Here we detail a combined method to make ultrasensitive water-processed photodetectors based on high-performance Langmuir–Blodgett (LB) monolayer transistors of semiconducting copper phthalocyanine (CuPc), using quasi one-dimensional (1D) ballistically-conductive single-walled carbon nanotubes (SWNTs) as point contacts. Operating at low biases, the monolayer photodetectors exhibit responsivities greater than 108 A W−1, detectivities greater than 7 × 1015 Jones, and high reproducibility. These results form the basis for new types of high-performance photodetectors for a variety of possible sensor applications.
Chemical Science 03/2011; 2(4):796-802. · 8.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The controllable deformation of nanopores was realized by moving a convergent electron beam in a high-resolution transmission electron microscope. Nanostructures with the desired geometries were successfully fabricated from the original nanopores in 100 nm-thick and 260 nm-thick Si(3)N(4) membranes. The formation dynamics is a competition process between the knock-on effect of the high-energy electron beam and surface tension driven shrinkage. This approach can be used to finely tune critical dimensions and deform nanopores to particular desired geometries with single-nanometer precision, which offers substantial opportunities in flexibly fabricating nanostructures for various applications such as nanoelectronics and nanofluidics.
[Show abstract][Hide abstract] ABSTRACT: Filling in the gap: Label-free, real-time electrical detection of proteins is achieved with high selectivity and real single-molecule sensitivity by using aptamer-functionalized molecular electronic devices with single-walled carbon nanotubes as point contacts.
Angewandte Chemie International Edition 03/2011; 50(11):2496-502. · 13.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Problems associated with intrinsically destructive sensing mechanisms of organic field-effect transistors constitute one of the main obstacles to using them for the practical applications in sensing and switching. Here we report a smart system, in which a photochromic spiropyran (SP) combined with polymethyl methacrylate (PMMA) is used as a gate dielectric, to develop functional molecular devices capable of photoswitching their electrical conductivity in a noninvasive manner. Significant and reversible capacitance and current transitions in devices are generally demonstrated experimentally when the SP molecules undergo their documented reversible photoisomerization. This concept of conformation-induced capacitive coupling offers attractive new prospects for the development of functional devices by utilizing other stimuli-responsive molecular materials.