The Pharmacological Basis of Therapeutics A Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. By Prof. Louis Goodman and Prof. Alfred Gilman. Pp. xiii + 1383. (New York: The Macmillan Company, 1941.) 50s. net.

The Pharmacological Basis of Therapeutics

http://nathan.instras.com/documentDB/paper-69.pdf

Porous silicon: a quantum sponge structure for silicon based optoelectronics

Conducting polymers in chemical sensors and arrays

Basic tools of analytical chemistry the language of analytical chemistry evaluating analytical data calibrations, standardizations, and blank corrections equilibrium chemistry obtaining and preparing samples for analysis gravimetric methods of analysis titrimetric methods of analysis spectroscopic methods of analysis electrochemical methods of analysis chromatographic and electrophoretic methods kinetic methods of analysis developing a standard method quality assurance.

Modern Analytical Chemistry

Research in the field of biosensors has enormously increased over the recent years. Since the development of the first biosensor by Clark in 1962, where an amperometric oxygen electrode was immobilised with an enzyme (glucose oxidase),1 many efforts have been invested to create functional hybrid systems. These functional hybrid systems often benefit from the coupling of the unique recognition and signal-amplification abilities of biological systems, that have been developed and optimised during millions of years of evolution, with an artificial man-made signal detection and amplification system. Thus, the combination of knowledge in bioand electrochemistry, solid-state and surface physics, bioengineering, integrated circuit silicon technology and data processing offers the possibility of a new generation of highly specific, sensitive, selective and reliable micro (bio-)chemical sensors and sensor arrays. Moreover, the rapid development of silicon technology has stimulated the fabrication of miniaturised analytical systems such as mTAS (micro total analysis system), ‘lab on chip’ sensors, electronic tongue devices and electronic noses.2–17 Among the variety of proposed concepts and different types of biosensors, the integration of biologically active materials together with an ISFET (ion-selective field-effect transistor) is one of the most attractive approaches. The ISFET was invented by Bergveld18 in 1970 and has been introduced as the first miniaturised silicon-based chemical sensor. In spite of distinct difficulties with regard to practical applications, the great interest in ISFET-based biosensors, so-called biologically modified field-effect transistors (BioFETs), has generated a great number of publications, a flow that shows no sign of diminishing. The reason therefore is that silicon-based fieldeffect devices are currently being the basic structural element in a new generation of micro biosensors; they provide a lot of potential advantages such as small size and weight, fast response, high reliability, low output impedance, the possibility of automatic packaging at wafer level, on-chip integration of biosensor arrays and a signal processing scheme with the future prospect of low-cost mass production of portable microanalysis systems; moreover, their possible field of applications reaches from medicine, biotechnology and environmental monitoring through food and drug industries to defence and security. This paper gives a review of recent and significant advances in the research and development of BioFETs. In planing this review, we have chosen to focus mainly upon developments occurring during the last six years (from 1995 to the end of 2001). A computer search of the Science Citation Index has found that more than 400 publications concerning ISFETs and BioFETs have appeared from January 1995 to December 2001, indicating the intensity of research activities devoted to this important task. This review is in general limited to journal articles and usually does not include patents, conference proceedings, reports or PhD theses. Some references to important works reported prior to 1995 have also been added to provide additional source material. The review is organised as follows: The principles of the ISFET and BioFET are described in section 2. Recent advances in the development of various types of BioFETs are reviewed in section 3. Here, some examples of current applications of BioFETs are presented, too. Concluding points and future prospects of BioFETs are discussed in section 4. Michael J. Schöning was born in Bruchsal, Germany, in 1962. He received his diploma in 1989 and Ph.D. in 1993, both in electrical engineering, from the Technical University (TH) Karlsruhe. In 1989 he joined the Institute of Radiochemistry at the Research Centre Karlsruhe, Germany. Since 1993 he has been with the Institute of Thin Films and Interfaces at the Research Centre Jülich, and since 1999 he has been a Professor of applied physics at the University of the Applied Sciences Aachen, Germany. His research interests include silicon-based chemical and biological sensors, thin film techniques, solid-state physics, semiconductor devices and microsystem technology.

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Recent advances in biologically sensitive field-effect transistors (BioFETs)

Nanoscale science and technology is today mainly focused on the fabrication of nanodevices. Our approach makes use of lithography processes to build the desired nanostructures directly. The fabrication process involves an electron-beam lithography technique to define metallic microstructures onto which nanometre scale patterning is performed using an atomic force microscope (AFM) as a mechanical modification tool. Both direct material removal and AFM-assisted mask patterning are applied in order to achieve the smallest possible separation between electrode pairs. The sample preparation involves a polymer deposition process that results in conformal growth and in surface roughness comparable to that of the substrate. The results of the application of this technique show that the process is reproducible and exhibits a good operation control during the lithographic steps, both ensured by the imaging facilities of the AFM. The nanolithography technique has been used to fabricate nanogap electrodes to be used for molecular devices. The study reported here can be considered as a reliable starting point for the development of more complex nanodevices, such as single-electron transistors.

https://iopscience.iop.org/article/10.1088/0957-4484/10/4/317/pdf

Atomic force microscopy lithography as a nanodevice development technique

Sequential addition of a polyanion, poly(styrene sulfonate), and a polycation, polyaniline, lead to the formation of layer-by-layer films at different solid surfaces. The prime variables which determine the films formation of poly(styrene sulfonate) (PSS)/polyaniline (PANI) were the polymer charge and ionic strength. The films were deposited by selecting organic/inorganic acid media at pH 2.8. The building up of such multilayer films was characterized by the increment of the adsorbed amount through UV−visible spectroscopy. A linear increase in the absorption magnitude was measured from 1 to 25 bilayers. The uniformity of the PSS/PANI layer-by-layer (LBL) films could be well-maintained, undoping the films in NaOH for obtaining an emeraldine base form of polyaniline. The built-up multilayers were investigated by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetric and electrical conductivity measurements. The interesting feature of the nearly equal grain size was noticed between 4...

Physical Properties of Polyaniline Films: Assembled by the Layer-by-Layer Technique

An in situ self-assembly technique with nanometre control over thicknesses and multilayered structures was used to manufacture the ultrathin films of polypyrrole (PPY). The PPY film was deposited on a polyanion, poly(styrene sulfonate) (PSS) modified surface as a function of time, previously PSS had been deposited on various substrates (glass, mica, indium-tin-oxide coated glass plates). Later, alternate PPY and PSS films were fabricated on such substrates using a layer-by-layer (LBL) technique. The glucose oxidase (GOD) molecules were also deposited on such self-assembled PPY films by the LBL technique. The PSS/PPY/GOD, PPY/PPY/GOD/poly(ethylene imine) (PEI)/GOD etc, film configurations were fabricated, and functionally as well as structurally characterized by UV-visible, electrochemical and scanning probe microscopy techniques, respectively. The results of a scanning probe microscopic study on the films were analysed to understand the molecular orientation of GOD on the PPY surface, and the dependence of the enzyme concentration for the depositing solutions. Moreover, the electrochemical studies performed provided information with respect to the electron transfer processes on the spatial arrangement of GOD molecules on the PPY surfaces. The immobilization of GOD on a conductive PPY represented a crucial and important step, and allowed us to construct the glucose-responsive biosensors.

http://iopscience.iop.org/article/10.1088/0957-4484/11/2/312/pdf

Nano-assembly of glucose oxidase on the in situ self-assembled films of polypyrrole and its optical, surface and electrochemical characterizations

Alternating photocurrent measurements with light-addressable potentiometric sensors (LAPSs) have been used to monitor pH, redox potential, and ionic concentrations at discrete locations in an electrolyte in contact with LAPS devices. We report here the results of AC photocurrent measurements with insulated semiconductor LAPS devices where the semiconductor either is illuminated through the insulator (frontside) or alternatively from the opposite side (backside). Such comparative AC photocurrent measurements were made with semiconductors of varied thickness, at varied frequency of light intensity modulation, and at several different photoexcitation wavelengths. The results are fit to a theoretical expression which predicts the dependence of photocurrent on modulation frequency, wafer thickness, bulk minority carrier lifetime, and surface recombination velocity. The results are useful to optimize the design of LAPS devices with regard to these parameters. The results also predict optimal conditions for minimal lateral spacing of adjacent sensing areas in LAPS devices.

Minority carrier diffusion length effects on light-addressable potentiometric sensor (LAPS) devices

Measurement of the ac photocurrent in metal/insulator/semiconductor capacitors can be used as a tool to measure minority‐carrier diffusion and lifetime. The amplitude of the ac photocurrent generated at a silicon surface biased into inversion depends on the number of excess minority carriers present at that surface. By comparing this amplitude when intensity‐modulated light is directed to each side of the same device, minority‐carrier diffusion from the back to the front of the device can be characterized. An analytical model of this transport process predicts the dependence of the ac photocurrent on frequency and wafer thickness, and allows the determination of a value of the bulk lifetime free of the influence of surface recombination. Measurements under low‐light intensity levels are presented on n‐type silicon wafers with lifetimes in the 10–100 μs range. Lifetimes are found about a factor of 2 lower than those measured with noncontact photoconductive decay, at high‐light intensity levels. This is exp...

Manuela Adami

Papers

Atomic force microscopy lithography as a nanodevice development technique

Physical Properties of Polyaniline Films: Assembled by the Layer-by-Layer Technique

Nano-assembly of glucose oxidase on the in situ self-assembled films of polypyrrole and its optical, surface and electrochemical characterizations

Minority carrier diffusion length effects on light-addressable potentiometric sensor (LAPS) devices

Investigation of carrier transport through silicon wafers by photocurrent measurements