The Zink Group
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Click on a person to see his/her research interest.
From left to right, top to bottom: Yan-Li Zhao, James Teh, Monty Liong, Rachel Stephenson, Dr. Zink, Li Du, Daniel Ferris, Zongxi Li, Travis Pecorelli, Tania Guardado, Philip Rutkowski, Eunshil Choi, Matt Kiesz, Yaroslav Klichko, Min Xue, Yuen Lau, Courtney Thomas, Marcelle Dibrell, Sanaz Kabehie, Bryana Henderson, Ryan Hoekstra, Melissa Russell
Camera shy: Derrick Tarn
Last Updated: June, 2009
Eunshil Choi
echoi@chem.ucla.edu
Mesoporous organic-inorganic hybrid materials are attractive because of their symbiotic properties that result from the organic functionalities and the thermal stablilties of the silica frameworks. Based on such advantages of hybrid materials, my research is focused on the syntheses and applications of molecular machines attached to the pore walls of the mesoporous silica materials. Specifically, I am interested in the light-induced molecular impellers which respond to specific wavelengths so as to control the trap and the release of guest molecules. Especially to apply such photo-responsive machines as a nano-valve in the living cells, my research is paid attention to the syntheses of smaller particles with the molecular machines.
Marcelle Dibrell
mdibrell@chem.ucla.edu
My research is concerned with Excited State Mixed Valence molecules, that is, molecules that have two or more equivalent sites that have different oxidation numbers in the excited state, but symmetrical charge distribution in the ground state. To study this phenomenon, the charge transfer region of the absorption spectrum is examined, showing the characteristic multiple bands due to the coupling that can exist between the excited states. It is the goal of the project to calculate this region of the absorption spectrum by using the relationship between the absorption spectrum and the molecular vibrations that are enhanced in a resonance raman spectrum, that is the vibrations that also play a role in electronic transitions.
Li Du
lidu@chem.ucla.edu
The research I am currently working on in the Zink group involves the synthesis and study of functional hollow mesoporous silica nanoparticles. The hollow materials with large volume space are derivatized with functional molecules to produce useful supramolecular nanovalves with a variety of interesting applications. I am currently interested in trying to design a pH-responsive nanovalves so that they are bio-friendly for use in drug delivery applications.
Daniel Ferris
dferris@chem.ucla.edu
The functional mesostructured materials for controlled release division of the Zink group focuses on three general aims. First, work continues on the nano-particles itself by changing the structure of the MCM-41 to increase its versatility. Second, many new organic molecules are being tested as nano-valves for controlled release. Lastly, different molecules are being attached to the surface of the particles in order to generate a cellular response that can lead to a cell targeting system. My work in the Zink group deals with both the nano-valve project as well as the cell-targeting project.
My primary research project deals with the generation of a light responsive nano-valve. A light controlled system has many advantages, including the dependence on the specific wavelength of light to induce motion (so that the release is not spontaneous) as well as the low invasiveness of light as an external control mechanism. The current design deals with a light sensitive organic molecule that is positioned at the MCM-41 pore entrance. The particle can be loaded with drug, which is held in the pore by introducing a capping agent that blocks the pore by associating with the organic thread. The organic thread absorbs light at a specific wavelength, and in doing so undergoes a photo-physical change, causing the release of the capping agent. This allows the drug to diffuse out of the MCM-41.
Of equal importance to how a drug is released is the ability to control where the drug is released. In order to send these drug containing particles to where they are needed, a specific chemical signal needs to be attached to the surface of the particles. I am most interested in the use of biomolecules to perform this function. If a biomolecule can be identified that activates endocytosis in a very specific cell line, then its presence on the surface of the nano-particle has the potential to be a cell specific targeting agent. This application has a wide variety of outlets from cancer treatment to in vivo genetic modification.
It will be very exciting for our lab if we can get both of these project integrated. This would be of greatest therapeutic benefit as the drug can be localized via the targeting system and then released by external irradiation. In turn, this could lead to treatment of many different problems affecting the medical field today.
Tania Guardado
tmguardado@ucla.edu
Bryana Henderson
bryana@chem.ucla.edu
I am currently involved in studies concerning photofragmentation of organometallic compounds in the gas phase. Visible and ultraviolet laser pulses intersect with jets of gas containing sublimed precursors, producing fragments that are analyzed with time-of-flight (TOF) and resonance-enhanced multi-photon ionization (REMPI) spectroscopy.
Fragmentation often depends on laser wavelength and fluence, and varying experimental parameters can give interesting insights into the processes involved during fragmentation. Although high mass peaks are common, metal and metal diatomic ions are usually among the most intense peaks in the spectra. Since thin films of metals and select metal diatomics are potentially useful for a wide range of applications (especially electronics), this research lays the foundation for development of new and improved thin films.
Ryan Hoekstra
hoekstry@chem.ucla.edu
I study the the spectroscopic consequences of intramolecular charge transfer using a Marcus-Hush type model and time dependent quantum mechanics. Work on this project involves not only the development of theoretical methods but also spectral characterization of specific examples to confirm/develop theory. Further information available upon request.
Sanaz Kabehie
sanaz@chem.ucla.edu
Nanomachines are based on changes in molecular bonding that result from chemical-, electrochemical-, or photo-induced changes in the electronic state of a nanostructure. A successful design of a functional nanomachine is comprised of three parts (1) a stationary component, (2) an axle, and (3) a rotator. The goal to further miniaturize information processing of today's technology is generating great interest in nanomachines and is a lead into the wonderful world of nanotechnology.
Matt Kiesz
mkiesz@chem.ucla.edu
My research utilizes absorption, resonance Raman, and emission spectroscopies in combination with the time-dependent theory of spectroscopy as a means of studying molecules in the excited state.
Yaroslav Klichko
yaroslav@chem.ucla.edu
My research involves design and synthesis of functional materials, which are based on mesoporous thin films. These films serve as a substrate or a framework for attachment of molecular machines such as rotaxanes or azobenzenes. Through careful positioning of the molecules inside mesoporous materials we are able to make molecular devices or novel materials with unique properties.
Yuen Lau
ylau@chem.ucla.edu
I am interested in studying the properties and exploring the various applications of functional organosilica materials.
In particular, the type of mesoporous nanoparticles (MSN) that I am currently studying, synthesized by Inagaki et al, exhibits a crystal-like periodic pore wall structure. The composition of the pore wall consists of a continuum of sets of silicate molecules sandwiching between a biphenylene functional group. The periodicity in conjunction with a large network of resonance along the pore wall has distinguished these MSN from the rest of its family. Upon derivatizing this special type of MSN with functional molecules like rotaxanes and pseudorotaxanes, this new class of material can act as a cargo carrier and release guest molecules that were loaded inside the nanopores, in a controllable fashion via light or chemical stimuli. Another unique feature manifests by these MSN is its capability of being photoactive without any incorporation of photosensitizers. Hopefully, more experiments with various functionalized molecules will be performed to further understand the full chemical properties of this new class of MSN.
Secondly, I am also interested in the biological application of some functionalized organosilica particles that have been studying in our group. More specifically, I am testing their applicabilities in delivering drugs inside cancer cells in a more target-oriented manner.
Zongxi Li
zongxili@chem.ucla.edu
Mesoporous silica nanoparticles functionalized by rotaxanes and pseudorotaxanes as nanovalves and by azobenzene as nanoimpellers have shown interesting control release properties. The purpose of my research is to combine the two kinds of machines to obtain the dual controlled mesoporous silica nanoparticles. I am also interested in visualizing the control release process of nanomachines in living cells using fluorescent microscope.
Monty Liong
mshliong@ucla.edu
Fluorescent mesoporous silica particles
Travis Pecorelli
tpecorel@chem.ucla.edu
My research investigates organic/inorganic hybrid mesoporous frameworks for attaching molecular machines. Highly ordered conjugated spacers, i.e. biphenyl or benzene, within the mesoporous silica allow for experiments involving photochemistry and electron transfer.
Another aspect of the reserach is to break out from exclusively silica frameworks to other transition metal oxide nanoparticles to support molecular machines. The most promising example would be titanium dioxide and possibly other transitional metal oxides.
Melissa Russell
mmrussell@ucla.edu
Philip Rutkowski
prutkow@chem.ucla.edu
Gas phase photofragmentation of organometallic precursors used in laser assisted chemical vapor deposition
Rachel Stephenson
rachels@chem.ucla.edu
The research I do in the Zink lab looks to answer questions about what is happening when a molecule is in its excited state. The majority of my work uses resonance Raman spectroscopy to look at the vibrational components of electronic transitions. Knowing what vibrations are active and by how much can help to characterize a charge transfer process, for example. Modeling the systems using the time-dependant theory of spectroscopy can help to pull out from the experimental data parameters of the system such as geometry changes, damping and coupling to other excited states. One part of my research looks to expand our current work on Excited State Mixed Valence (ESMV) by looking at compounds involving one or more transition metals. Example compounds have copper, ruthenium and platinum metal components. A second area of my research looks specifically at the involvement of a solvent in the charge transfer processes. The solvent-solute interaction can be very important and can dramatically change the observed spectroscopic features but separating the solvent contributions from the solute contributions can be difficult. The effect of other coupled states is also investigated in addition to the solvent effects.
Derrick Tarn
dtarn@ucla.edu
James Teh
gxj2s2@hotmail.com
Courtney Thomas
courtney.thomas@chem.ucla.edu
Mesoporous silica nanoparticles are of particular interest due to their highly ordered and uniform pores. The hydrophobic nature of the interior of the pores, as well as the ability to functionalize the silica surface with hydrophilic functionalities, makes these particles attractive for anti-cancer drug delivery. I am currently working on a few variations of the basic silica nanoparticles. Adding a magnetic core to the particles is of interest for its potential applications in magnetic resonance imaging, as addition of the magnetic core may make it useful as a contrast agent. Additionally, functionalizing the surface of the particles is important so that particular cells are targeted. Since current cancer therapeutics involve targeting a region of cells, being able to deliver anti-cancer drugs only to the cancer cells without affecting healthy cells would be very beneficial.
Min Xue
mxue@chem.ucla.edu
My research is currently on pH-responsive nanovalves based on pseudorotaxanes. These nanovalves could be modified for different operation conditions. I'm also trying to combine this system with other nanomachines such as "snap-top" or nanoimpeller to build a pH/enzyme or pH/light dual-control system. All these systems are designed for bio-applications such as cancer cell targeting and drug delivery.
Yan-Li Zhao
ylzhao@chem.ucla.edu
With increasing demands to manage the activation of controlled release system for drug delivery applications, new hybrid materials are being sought. A lot of my effort in Prof Zink's group has devoted into the construction of biocompatible mechanized mesoporous silica nanoparticles that respond to external stimuli such as light and pH changes or specific enzyme targets. The research goal is to achieve controlled and on-demand release of anti-cancer drugs into human cells.