Detection of nanoparticles suspended in a light scattering medium

Intentionally intensifying the light scattering of medium molecules can allow the detection of suspended nanoparticles under conditions not suitable for conventional optical microscopies or laser particle counters. Here, we demonstrate how the collective light scattering of medium molecules and nanoparticles is imaged in response to the power, frequency, and oscillating direction of the incident light wave electric field, and how this response can be used to distinguish between nanoparticles and microparticles, such as viruses or bacteria. Under conditions that the medium light scattering is intensified, suspended nanoparticles appear as magnified shiny moving dots superimposed on the quasi-steady background of medium light scattering. Utilizing the visual enlargement resulted from the enhanced light scattering and possible light interference, we can detect directly suspended nanoparticles that are much smaller than visible light wavelengths even in unopened water bottles or other large containers. This suggests new approaches for detecting nanoparticles with many potential applications.

2D Octagon-Structure Carbon and Its Polarization Resolved Raman Spectra

We predict a new phase of two-dimensional carbon with density functional theory (DFT). It was found to be semimetal with two Dirac points. The vibrational properties and the polarization resolved Raman spectra of the carbon monolayer are predicted. There are five Raman active modes: 574 cm−1 (Eg), 1112 cm−1 (B1g), 1186 cm−1 (B2g), 1605 cm−1 (B2g) and 1734 cm−1 (A1g). We consider the incident light wave vector to be perpendicular and parallel to the plane of the carbon monolayer. By calculating Raman tensor of each Raman active mode, we obtained polarization angle dependent Raman intensities. Our results will help materials scientists to identify the existence and orientation of octagon-structure carbon monolayer when they are growing it.

Fourier Analysis of Digital STEM Images in the Study of Transparency in Human Cornea And Sclera

The structure of transparent human cornea is similar to that of the opaque human sclera, and they both consist of collagen fibers embedded in a mucopolysaccharide matrix.[1] This similarity in structure and composition, in contrast to a large difference in turbidity, presents an important question regarding the basis of transparency in the cornea.In general, a transparent structure permits most of the incident light to be transmitted, whereas an opaque structure scatters it. Scattering of an incident light wave occurs when the spatial fluctuations in the index of the refraction of the medium have dimensions close to the wavelength of visible light.[2] To analyze spatial fluctuations in cornea and sclera we have developed techniques based on Fourier analysis of digital STEM images.Fourier analysis allows direct quantitative measurements of the fluctuations in any signal. The signal is resolved into its constituent sinusoids or Fourier components. Amplitude, and frequency of each component are quantitatively obtained using the Fourier Transform (FT).