Biomedical subjects

Haohua Tu

Publications and source records attributed to Haohua Tu.

3 recordsLinked to original sources

PubMed2006

Investigation of concentrically and eccentrically layered droplets by light scattering.

Two pairs of immiscible liquid compounds are chosen to prepare levitated layered droplets with and without density difference between core and layer phases. The droplets are examined by light scattering along two orthogonal directions. A layered droplet without phase density difference is unambiguously identified as a concentric sphere by matching the observed scattering spectra with those calculated from the Aden-Kerker extension of Mie theory. For layered droplets with phase density difference, only the scattering spectrum from one of the scattering directions can be matched theoretically. These observations suggest that a static layered droplet is predominantly eccentric even though the embedded core is large by volume, as predicted from fluid mechanics. The consistency of the light-scattering characterization with the diffusion theory governing the evaporation of concentrically and eccentrically layered droplets is also established.

Journal Article↗

PubMed2006

Photoinduced direct electron transfer from InSe to GaSe semiconductor nanoparticles.

Direct electron transfer from InSe nanoparticles to GaSe nanoparticles in mixed solution-phase aggregates has been found to occur upon photoexcitation. Mixed aggregates exhibit a strong charge-transfer absorption band at an energy slightly higher than the InSe band gap. Photoexcitation of this band results in a polarized transient absorption spectrum and transient absorption kinetics characteristic of InSe valence-band holes and GaSe conduction-band electrons. The kinetics indicate that charge separation persists for at least several hundred picoseconds.

Journal Article↗

PubMed2005

Charge limits on droplets during evaporation.

We have examined charge stability limits of single evaporating microdroplets that were suspended in an electrodynamic balance. A high precision light scattering technique based on optical resonances was used to determine the size and the size change of a droplet at a charge instability induced breakup. The charge level and the charge loss at the breakup were obtained from the dc voltages required to balance the droplet prior to and following the breakup. The results on droplets of diethyl phthalate (DEP), diethylene glycol (DEG), triethylene glycol (TEG), and hexadecane show that breakups due to the charge instability occur at the Rayleigh charge limit. The observed charge losses during breakups range from about 15.3% for hexadecane droplets to about 41.1% for TEG droplets. Hexadecane droplets lose about 1.5% of their mass, while DEP droplets, about 2.3%. Within the detectable limit of 0.03%, no mass losses were observed during breakups of DEG and TEG droplets. The observation of extremely low mass losses that accompany high charge losses from DEG and TEG droplets suggests that the process of breakups of DEG and TEG droplets is distinct from that of DEP and hexadecane droplets. An analysis of the results indicates that breakups of DEP and hexadecane droplets result in the formation of a few large progeny droplets, while TEG and DEG droplets produce thousands of fine progeny droplets.

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