This paper demonstrates a novel facile method for fabrication of patterned arrays of gold nanoparticles on Si/SiO2 by combining electron beam lithography and self-assembly techniques. Our strategy is to use direct-write electron beam patterning to convert nitro functionality in self-assembled monolayers of 3-(4-nitrophenoxy)-propyltrimethoxysilane to amino functionality, forming chemically well-defined surface architectures on the 100 nm scale. These nanopatterns are employed to guide the assembly of citrate-passivated gold nanoparticles according to their different affinities for amino and nitro groups. This kind of nanoparticle assembly offers an attractive new option for nanoparticle patterning a silicon surface, as relevant, for example, to biosensors, electronics, and optical devices.

The three-dimensional ultrasound-assessed thigh volume has better accuracy in predicting birth weight than the commonly used formulas by two-dimensional ultrasound, and it may improve fetal weight prediction in clinical practice. However, a large-scale prospective validation study may be needed to confirm our conclusions.

Time-lapse studies of a film of passivated gold nanoparticles under electron beam irradiation have been performed using a transmission electron microscope, revealing the microscopic dynamics of the sintering process at the single nanoparticle level. It is found that the sintering of individual passivated gold nanoparticles under electron irradiation is local and mainly depends on the sensitivity of the passivating ligands to the electron beam. A multilayer film is less stable than monolayer film, consistent with the enhanced generation of secondary electrons. The observations also reveal a significant difference between the sintering of passivated nanoparticles and bare metal particles, especially regarding the size effect on the sintering rate. The formation of a neck between adjacent nanoparticles further indicates a mechanism driven by surface diffusion rather than Ostwald ripening at the initial sintering stage.