Silicon diffused diodes with nearly ideal current-voltage characteristics

It is shown that nearly ideal current-voltage characteristics (I-V curves) can be obtained for small-area, shallow silicon diffused p-n junctions irradiated with ⁶⁰Co gamma rays in the dose range 10³–5×10⁵ Gy. In the irradiated diodes the current transfer mechanism is observed to shift from generation-recombination to diffusion. The nonideality factor on the forward branch of the I-V curve decreases from 1.68 in the unirradiated diode to 1.17 in a diode irradiated to a dose of 5×10⁵ Gy. A saturation current is observed on the reverse branch of the I-V curves of irradiated diodes at room temperature. Zh. Tekh. Fiz. 68, 131–132 (October 1998)     

Effect of the local environment and state of the immobilized ligand on its reaction with a macromolecular receptor

We consider a simple statistical model for interaction between a macromolecular receptor and a surface functionalized with low molecular weight ligands of the same type. For the example of the reaction between immobilized sulfamethoxazole and a selective antibody, we have used surface plasmon resonance to demonstrate that the proposed approach is appropriate for describing the dependence of the adsorption capacity on the surface density of the immobilized ligand and its charge state. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 210–216, July–August, 2006.     

Interface functional architecture using mixed thiol monolayers: Effect of the composition and spatial organization on the immobilization of low-molecular-weight ligands

A simple procedure is examined for forming a selective sensor coating using mixed self-assembling thiol monolayers functionalized by molecules of the sulfanilamide antibiotic, sulfamethoxazol (SMX). A model is proposed for the interface processes, which accounts for the complex dependence of the adsorption capacity of the coatings obtained on the surface density of the reactive groups and the low adsorption capacity at high reaction site concentrations. The model was supported by competitive inhibition analysis. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 158–164, May–June, 2008.     

Simple analytical model of biosensor competition analysis for detection of low-molecular-weight analytes

A steady-state model of competition inhibitor analysis and its application to the detection of sulfamethoxazole in aqueous solutions (0.01–100 μg/mL) using surface plasmon resonance are examined. An analytical expression (logistic curve) relating the equilibrium response of the biosensor to the concentration of the low-molecular-weight analyte, its immobilized analogue, and the biological receptor was obtained. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 96–101, March–April, 2006.     

The effect of low pH on the glycitein-BSA conjugate interaction with specific antiserum: competitive inhibition study using surface plasmon resonance technique

Competitive inhibition serological assay for detection of the phytoestrogen glycitein (Glyc) was developed using surface plasmon resonance (SPR) technique with protein conjugates and polyclonal antibodies initially designed for the enzyme-linked immunosorbent assays (ELISA). The efficiency of the approach to the quantification of the soy isoflavone glycitein in water was investigated using the competitive reaction of analyte (free Glyc)and immobilized Glyc-BSA-conjugate with polyclonal antibodies. It was shown that the efficiency to detect Glyc drastically depends on the pH level of the probe solution. With the decrease in pH from 7.4 to 4.0, (i) the affinity of the specific reaction increases and (ii) the level of unspecific sorption becomes saturated. Non-specific adsorption to a SPR sensor surface obscures the specific component and shaded specific response at higher pH (6.0-7.4) when used serum for the quantification of specific analytes. The standard curves obtained in acidic solutions (pH 4-5) indicate that the linear part of the dependence completely covers the range between detection limit (0.1 μg/ml) and Glyc solubility in water (0.9 μg/ml). The difference in SPR- and ELISA-based analytical protocols as well as the requirements for increasing the efficiency in quantitative SPR analysis using purified antibodies is discussed.     

Measurement uncertainty in analytical studies based on surface plasmon resonance

The sensitivity of surface plasmon resonance (SPR) transducers depends on the thickness and spatial organization of interfacial structures at their surfaces. This is because the response of the SPR sensor is determined by integrating the distance-dependent refractive index (spatial interfacial architectures), weighted by the square of the electromagnetic field, from zero to infinite distance. The effect of SPR transducer sensitivity variation on the accuracy of SPR analysis is considered. Our quantitative estimation (based on the results of refractometric studies) gave a value for sensitivity variation of about 3% for the formation of a self-assembled thiocyanate layer or a trypsin-soybean trypsin inhibitor surface complex. The estimated accuracy in measured variation (i.e., by 0.01) for the refractive index of the external medium was 3 × 10⁻⁴. This restriction, which follows immediately from the physical mechanism of the SPR phenomenon, should be taken into account when analyzing data obtained with the above technique.     

Phase interactions in TiN<Subscript>x</Subscript>(TiB<Subscript>x</Subscript>)-<Emphasis Type="Italic">n</Emphasis>-Si-<Emphasis Type="Italic">n</Emphasis><Superscript>+</Superscript>-Si contacts and their thermal degradation due to rapid thermal annealing

The temperature stability of TiN_x(TiB_x)-n-Si-n ⁺-Si, Au-TiN_x(TiB_x)-n-Si-n ⁺-Si, and Au-Ti(Mo)-TiN_x(TiB_x)-n-Si-n ⁺-Si Schottky-barrier contacts subjected to rapid thermal annealing in hydrogen at temperatures T=400, 600, and 800°C is studied. It is shown that structural and morphological transformations and the related degradation of electrophysical characteristics in interstitial alloys (titanium nitrides and borides) start at 600°C. Reasons for the degradation of the barrier properties of titanium borides and nitrides are discussed.     

SPR Study of the Blocking Activity of Soybean Trypsin Inhibitor by Macrocyclic Complexes of Nickel Immobilized on a Gold Surface

A method is proposed for the modification of metallic gold surfaces by self-organization of a nickel(II) macrocyclic complex containing a thiol substituent. Effective blocking of biologically active soybean trypsin inhibitor by the immobilized complex was observed. The prospects of using the given surface to create sensitive elements for sensors capable of detecting both small molecules (thiocyanate ions) and some protein substrates is demonstrated.     

Integrated microwave (centimeter-range) modulator on polycrystalline diamond layers

Measuring data for the parameters of a microstrip switching superhigh-frequency integrated circuit on a 100-μm-thick polycrystalline diamond film are reported. Measurements are taken in the frequency range 3–7 GHz. It is shown that the decay in developmental modulators is no greater than 1.5 dB in the on state and no less than 29 dB in the off state. Physicochemical analysis of the multilayer contact metallization technology as applied to synthetic diamond and a silicon p-i-n diode is carried out. The metallization is shown to be stable up to 400°C.     

Nanosized magnetic composite for extraction of γ-immunoglobulins from biological media

By immobilization of protein A on the surface of magnetic Fe₃O₄ nanoparticles, coated with a tin(IV) hydroxide shell, we have obtained a magnetic nanosorbent selectively interacting with immunoglobulins. We have demonstrated that the sorbent obtained can be used to selectively extract immunoglobulins from biological media. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 204–209, July–August, 2006.