3 research outputs found
Volumetric Temperature Mapping Using Light-Sheet Microscopy and Upconversion Fluorescence from Micro- and Nano-Rare Earth Composites
We present a combination of light-sheet excitation and two-dimensional fluorescence intensity ratio (FIR) measurements as a simple and promising technique for three-dimensional temperature mapping. The feasibility of this approach is demonstrated with samples fabricated with sodium yttrium fluoride nanoparticles co-doped with rare-earth ytterbium and erbium ions (NaYF4:Yb3+/Er3+) incorporated into polydimethylsiloxane (PDMS) as a host material. In addition, we also evaluate the technique using lipid-coated NaYF4:Yb3+/Er3+ nanoparticles immersed in agar. The composite materials show upconverted (UC) fluorescence bands when excited by a 980 nm near-infrared laser light-sheet. Using a single CMOS camera and a pair of interferometric optical filters to specifically image the two thermally-coupled bands (at 525 and 550 nm), the two-dimensional FIR and, hence, the temperature map can be readily obtained. The proposed method can take optically sectioned (confocal-like) images with good optical resolution over relatively large samples (up to the millimetric scale) for further 3D temperature reconstruction
Physicochemical Study of Viral Nanoparticles at the Air/Water Interface
The assembly of most single-stranded
RNA (ssRNA) viruses into icosahedral
nucleocapsids is a spontaneous process driven by proteinâprotein
and RNAâprotein interactions. The precise nature of these interactions
results in the assembly of extremely monodisperse and structurally
indistinguishable nucleocapsids. In this work, by using a ssRNA plant
virus (cowpea chlorotic mottle virus [CCMV]) as a charged nanoparticle
we show that the diffusion of these nanoparticles from the bulk solution
to the air/water interface is an irreversible adsorption process.
By using the Langmuir technique, we measured the diffusion and adsorption
of viral nucleocapsids at the air/water interface at different pH
conditions. The pH changes, and therefore in the net surface charge
of the virions, have a great influence in the diffusion rate from
the bulk solution to the air/water interface. Moreover, assembly of
mesoscopic and microscopic viral aggregates at this interface depends
on the net surface charge of the virions and the surface pressure.
By using Brewsterâs angle microscopy we characterized these
structures at the interface. Most common structures observed were
clusters of virions and soap-frothlike micron-size structures. Furthermore,
the CCMV films were compressed to form monolayers and multilayers
from moderate to high surface pressures, respectively. After transferring
the films from the air/water interface onto mica by using the LangmuirâBlodgett
technique, their morphology was characterized by atomic force microscopy.
These viral monolayers showed closed-packing nano- and microscopic
arrangements