Bio-inspired photoresponse of porphyrin-attached gold nanoparticles on a field-effect transistor.

A bio-inspired photoresponse was engineered in porphyrin-attached Au nanoparticles (AuNPs) on a field-effect transistor (FET). The system mimics photosynthetic electron transfer, using porphyrin derivatives as photosensitizers and AuNPs as photoelectron counting devices. Porphyrin-protected AuNPs were immobilized onto the gate of an FET via the formation of self-assembled monolayers. Photoinduced electron transfer from the porphyrin led to single electron transfer at the Au nanoparticles, which was monitored via a changing gate voltage on the FET in the presence of organic electrolyte. The further attachment of other functional molecules to this system should enable various other potential functionalities. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.

π-Conjugated nickel bis(dithiolene) complex nanosheet.

A π-conjugated nanosheet comprising planar nickel bis(dithiolene) complexes was synthesized by a bottom-up method. A liquid-liquid interfacial reaction using benzenehexathiol in the organic phase and nickel(II) acetate in the aqueous phase produced a semiconducting bulk material with a thickness of several micrometers. Powder X-ray diffraction analysis revealed that the crystalline portion of the bulk material comprised a staggered stack of nanosheets. A single-layer nanosheet was successfully realized using a gas-liquid interfacial reaction. Atomic force microscopy and scanning tunneling microscopy confirmed that the π-conjugated nanosheet was single-layered. Modulation of the oxidation state of the nanosheet was possible using chemical redox reactions.

Arranging Diamagnetic Particles in a Modulated Magnetic Field Originating in Microelectromechanical Systems Compatible with an Integrated Circuit upon Halbach Array Magnet.

In this study, we attempted to expand the applicability of the mechanism for arranging diamagnetic particles in a modulated magnetic field. A Halbach array magnet was prototyped as a portable device for generating a high magnetic field. Despite the magnet being palm-size with dimensions of 50 × 50 × 20 mm, the magnetic field is 1.31 T at 1 mm from the surface. Additionally, an Si substrate on which an Fe thin film is formed and patterned to be compatible with the integrated circuit (IC)-utilizing the microelectromechanical systems process technology-is prototyped as a tool to generate a modulated magnetic field. Regarding the deposition condition of the Fe thin film, holes with diameters of 30 µm are arranged in an array at intervals of 60 µm, and the thickness is approximately 0.5 µm. Finally, a particle magnetic-adsorption experiment was conducted using the prototypes. The diamagnetic particles (diameter: 25 µm) dispersed in the paramagnetic surrounding medium were observed to be arranged in the hole portions. This result indicates that the microparticles are absorbed in their arbitrary positions by the modulated magnetic field. In the end, we succeeded in achieving the portability and implementation on IC for the particle arrangement magnetic mechanism.

Solution-processed organometallic quasi-two-dimensional nanosheets as a hole buffer layer for organic light-emitting devices.

Two-dimensional (2D) vdW materials have been integrated into optoelectronic devices to achieve exceptional functionality. However, the integration of large-area 2D thin films into organic light-emitting devices (OLEDs) remains challenging because of the finite number of inorganic 2D materials and the high-temperature requirements of their deposition process. The construction of 2D organometallic materials holds immense potential because of their solution synthesis and unlimited structural and functional diversity. Here, we report a facile route using an oil-water interfacial coordination reaction between organic ligands and divalent metal ions to synthesize crystalline quasi-2D organometallic bis(dithiolato)nickel (NiDT) nanosheets with a centimeter scale and a tunable thickness. The NiDT nanosheets can be directly integrated into OLEDs for use as a hole buffer layer and a fluorescent mounting medium without the aid of a transfer process. Moreover, OLEDs with NiDT nanosheets show not only comparable efficiency to conventional OLEDs but also prolonged device lifetime by nearly 2 times. These results open up a new dimension to use quasi-2D organometallic nanosheets as functional layers in large-area organic devices.

An Integrated ISFET Sensor Array.

A monolithically integrated ISFET sensor array and interface circuit are described. A new high-density, low-power source-drain follower was developed for the sensor array. ISFETs were formed by depositing Au/Ti extended-gate electrodes on standard MOSFETs, then thin silicon nitride layers using catalytic chemical vapor deposition and/or SU-8 protective layers were formed on the extended-gate electrodes. Applications for the array include: (1) pH detection by statistical distribution observing time and space fluctuations; (2) DNA detection using thiol-modified or silane-coupled oligonucleotides; (3) bio-image sensing by converting photons to electrons using Photosystem I of Thermosynechococcus elongatus, and sensing the converted electric charges by ISFETs.

A 65-nm CMOS Fully Integrated Analysis Platform Using an On-Chip Vector Network Analyzer and a Transmission-Line-Based Detection Window for Analyzing Circulating Tumor Cell and Exosome.

A fully integrated CMOS circuit based on a vector network analyzer and a transmission-line-based detection window for circulating tumor cell (CTC) and exosome analysis is presented for the first time. We have introduced a fully integrated architecture, which eliminates the undesired parasitic components and enables high-sensitivity, to analyze extremely low-concentration CTC in blood. The detection window was designed on the high-sensitive coplanar waveguide line. To validate the operation of the proposed system, a test chip was fabricated using 65-nm CMOS technology. Measurements were performed after adding a tiny lump of silicone or a droplet of water on its detection window. The measured results show |S_21| degradation of -1.96 dB and -6.04 dB for the silicone and the droplet, respectively, at 1.4 GHz. In addition, in another measurement using magnetic beads, it is confirmed that the proposed circuit can analyze even low concentrations of 20 beads/µL. As well as microbeads, measurement with CTCs was successfully demonstrated.

Design and Experimental Verification of a 0.19 V 53 µW 65 nm CMOS Integrated Supply-Sensing Sensor With a Supply-Insensitive Temperature Sensor and an Inductive-Coupling Transmitter for a Self-Powered Bio-sensing System Using a Biofuel Cell.

In this paper, we present a self-powered bio-sensing system with the capability of proximity inductive-coupling communication for supply sensing and temperature monitoring. The proposed bio-sensing system includes a biofuel cell as a power source and a sensing frontend that is associated with the CMOS integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, a supply-insensitive time-domain temperature sensor, and a current-driven inductive-coupling transmitter and achieves low-voltage operation. The timer converts the output voltage from a biofuel cell to frequency. The temperature sensor provides a pulse width modulation (PWM) output that is not dependent on the supply voltage, and the associated inductive-coupling transmitter enables proximity communication. A test chip was fabricated in 65 nm CMOS technology and consumed 53 µW with a supply voltage of 190 mV. The low-voltage-friendly design satisfied the performance targets of each integrated sensor without any trimming. The chips allowed us to successfully demonstrate proximity communication with an asynchronous receiver, and the measurement results show the potential for self-powered operation using biofuel cells. The analysis and experimental verification of the system confirmed their robustness.

Development of Microelectrode Arrays Using Electroless Plating for CMOS-Based Direct Counting of Bacterial and HeLa Cells.

The development of two new types of high-density, electroless plated microelectrode arrays for CMOS-based high-sensitivity direct bacteria and HeLa cell counting are presented. For emerging high-sensitivity direct pathogen counting, two technical challenges must be addressed. One is the formation of a bacteria-sized microelectrode, and the other is the development of a high-sensitivity and high-speed amperometry circuit. The requirement for microelectrode formation is that the gold microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the dimensions of the microelectrodes on a CMOS sensor chip in this work were successfully reduced to 1.2 µm × 2.05 µm. This is 1/20th of the smallest size reported in the literature. Since a bacteria-sized microelectrode has a severe limitation on the current flow, the amperometry circuit has to have a high sensitivity and high speed with low noise. In this work, a current buffer was inserted to mitigate the potential fluctuation. Three test chips were fabricated using a 0.6- µm CMOS process: two with 1.2 µm × 2.05 µm (1024 × 1024 and 4 × 4) sensor arrays and one with 6- µm square (16 × 16) sensor arrays; and the microelectrodes were formed on them using electroless plating. The uniformity among the 1024 × 1024 electrodes arranged with a pitch of 3.6 µm × 4.45 µm was optically verified. For improving sensitivity, the trenches on each microelectrode were developed and verified optically and electrochemically for the first time. Higher sensitivity can be achieved by introducing a trench structure than by using a conventional microelectrode formed by contact photolithography. Cyclic voltammetry (CV) measurements obtained using the 1.2 µm × 2.05 µm 4 × 4 and 6- µm square 16 × 16 sensor array with electroless-plated microelectrodes successfully demonstrated direct counting of the bacteria-sized microbeads and HeLa cells.

Chemistry integrated circuit: chemical system on a complementary metal oxide semiconductor integrated circuit.

By integrating chemical reactions on a large-scale integration (LSI) chip, new types of device can be created. For biomedical applications, monolithically integrated sensor arrays for potentiometric, amperometric and impedimetric sensing of biomolecules have been developed. The potentiometric sensor array detects pH and redox reaction as a statistical distribution of fluctuations in time and space. For the amperometric sensor array, a microelectrode structure for measuring multiple currents at high speed has been proposed. The impedimetric sensor array is designed to measure impedance up to 10 MHz. The multimodal sensor array will enable synthetic analysis and make it possible to standardize biosensor chips. Another approach is to create new functional devices by integrating molecular systems with LSI chips, for example image sensors that incorporate biological materials with a sensor array. The quantum yield of the photoelectric conversion of photosynthesis is 100%, which is extremely difficult to achieve by artificial means. In a recently developed process, a molecular wire is plugged directly into a biological photosynthetic system to efficiently conduct electrons to a gold electrode. A single photon can be detected at room temperature using such a system combined with a molecular single-electron transistor.

Low-temperature fabrication of ZnO nanorods/ferrocenyl-alkanethiol bilayer electrode and its application for enzymatic glucose detection.

A novel ZnO nanorods/ferrocenyl-alkanethiol (FcC11SH) bilayer structure was prepared and applied for the fabrication of glucose enzymatic biosensor. ZnO nanorod matrix was synthesized by low temperature aqueous method and provided a favorable environment for the immobilization of glucose oxidase (GOx). A monolayer of FcC11SH molecular was self-assembled on the surface of gold electrode and introduced a shuttling way for electronic communication between GOx and electrode. The morphology and structure of prepared ZnO nanorods were characterized by employing scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). Electrochemcial measurements of the sensor revealed a high and reproducible sensitivity of 27.8 µA cm(-2) mM(-1), and a linear range from 0.05 to 1.0mM with a detection limit of 20 µM. A relatively low value of Michaelis-Menten constant about 2.95 mM indicates the enhanced affinity of GOx to glucose. To the best of our knowledge, this is the first time to fabricate the glucose biosensor by using ZnO and FcC11SH bilayer structure.

Fabrication of microspheres from phthalimide-substituted porphyrin derivatives.

Microspheres were fabricated from phthalimide-substituted porphyrin derivatives. Microscopic analysis showed that the structures of the supramolecular assemblies synthesized in the present study were spherical, with diameters in the sub-micrometer to micrometer range. The size of the microspheres could be controlled by changing the concentration of the casting solution. The spectroscopic properties of the microspheres were measured to determine the influence of their structural components. Thermal studies indicated that the temperature at which these structures became unstable was lower than the bulk melting point. During I-V measurements on devices composed of these microspheres, it was found that the current increased upon light irradiation, and the characteristic photoresponse properties of these devices were reproducible.

A photosensing system composed of photosystem I, molecular wire, gold nanoparticle, and double surfactants in water.

Photosensing performance of a system composed of photosystem I (PSI), vitamin K(1) (VK(1))-like molecular wire, and gold nanoparticles (AuNPs) in an aqueous solution was increased considerably by the addition of double surfactants, hexylamine and dodecylbenzenesulfonate.

Preparation of organic nanoscrews from simple porphyrin derivatives.

Twisted supramolecular assemblies "nanoscrews", were prepared by using simple porphyrin derivatives and acetonitrile solvent. The electrical properties of the assemblies were measured by using microgap electrodes. The nanoscrew had conductivity and showed photo-current. By changing the solvent, the pitch of the screws and their aggregation shapes could be controlled.

Photosensor based on an FET utilizing a biocomponent of photosystem I for use in imaging devices.

We have investigated a photosensor that consists of a field emission transistor (FET) utilizing the biocomponent of the photosystem I (PSI) protein complex for use in an imaging device. The PSI was immobilized on a gold electrode via the self-assembling monolayer (SAM) of 3-mercapto-1-propanesulfonic acid sodium salt to obtain a PSI-modified gold electrode. As for the PSI-modified gold electrode, the basic photoresponses originating from the excitation of PSI, including the photocurrent (106 nA) and the photoresponse of the open-circuit voltage (photo-Voc: 28.6 mV), were characterized. Then, the PSI-modified gold electrode was linked to the gate of the FET using a lead line, and the device was successfully driven by the photoelectric signals from the PSI like a voltage follower circuit. Further, we successfully demonstrated that the PSI-based FET acts as a photosensor in imaging devices.