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High density of crystal defects is formed in Si layers during their growth on the nanostructured surface composed of dense arrays of Ge islands grown on oxidized Si substrates. Although these defect-rich Si layers exhibit intense photoluminescence only at low temperatures, the forward-biased diodes with the Si layers located in the region of the p-i-n+ junction can emit light at room temperature. The difference suggests that the influence of thermal emission of carriers from defect states on the light emission intensity is essentially reduced when the spatial distribution of carrier density is governed by the bias voltage and band bending. The results show that Si layers emitting light in the 1.4–1.7 μm range at room temperature can be prepared by means of growth. [ABSTRACT FROM AUTHOR]

We show that it is possible to detect specifically adsorbed bacteriophage directly by breaking the interactions between proteins displayed on the phage coat and ligands immobilized on the surface of a quartz crystal microbalance (QCM). This is achieved through increasing the amplitude of oscillation of the QCM surface and sensitively detecting the acoustic emission produced when the bacteriophage detaches from the surface. There is no interference from nonspecifically adsorbed phage. The detection is quantitative over at least 5 orders of magnitude and is sensitive enough to detect as few as 20 phage. The method has potential as a sensitive and low-cost method for virus detection.

In the present work we use a thickness shear mode resonator-QCM operating at variable amplitude. Not frequency shift is recorded during the measurement but a sharp signal generated during the rupture of nanoparticles from the surface under smoothly increasing amplitude of oscillations. We consider the process of nanoparticle rupture from the QCM surface. The nature of signal formation is described, the motion of the nanoparticle and forces affecting it are considered. A connection between the properties of the ruptured particle with signal form (shape) is revealed. A sharp single peak is observed during the rupture of a rigid spherical nanoparticle, while the separation of long nanometer-sized particles bound along their length is accompanied by peak broadening. If a nanoparticle composed of separate smaller particles is detached from the surface, the particle decomposes into fragments, and the signal appears as a set of separate peaks. [ABSTRACT FROM AUTHOR]

A new method based on the use of quartz crystal microbalance (QCM) as an active sensing element is developed, optimized and tested in a model system to measure the rupture force and deduce size distribution of nanoparticles. As suggested by model predictions, the QCM is shaped as a strip. The ratio of rupture signals at the second and the third harmonics versus the geometric position of a body on QCM surface is investigated theoretically. Recommendations concerning the use of the method for measuring the nanoparticle size distribution are presented. It is shown experimentally for an ensemble of test particles with a characteristic size within 20-30 nm that the proposed method allows one to determine particle size distribution. On the basis of the position and value of the measured rupture signal, a histogram of particle size distribution and percentage of each size fraction were determined. The main merits of the bond-rupture method are its rapid response, simplicity and the ability to discriminate between specific and non-specific interactions. The method is highly sensitive with respect to mass (the sensitivity is generally dependent on the chemical nature of receptor and analyte and may reach 8×10(-14) g mm(-2)) and applicable to measuring rupture forces either for weak bonds, for example hydrogen bonds, or for strong covalent bonds (10(-11)-10(-9) N). This procedure may become a good alternative for the existing methods, such as AFM or optical methods of determining biological objects, and win a broad range of applications both in laboratory research and in biosensing for various purposes. Possible applications include medicine, diagnostics, environmental or agricultural monitoring., (Copyright © 2010 Elsevier B.V. All rights reserved.)

We have developed a sensitive, economical method that directly detects viruses by making use of the interaction between type 1 herpes simplex virus (HSV1) and specific antibodies covalently attached to the oscillating surface of a quartz crystal microbalance (QCM). The virions were detached from the surface by monotonously increasing the amplitude of oscillation of the QCM, while using the QCM to sensitively detect the acoustic noise produced when the interactions were broken. We term this process rupture event scanning (REVS). The method is quantitative over at least six orders of magnitude, and its sensitivity approaches detection of a single virus particle.