Development of targeted drug delivery systems for cancer and leukemia; design, synthesis and eval... more Development of targeted drug delivery systems for cancer and leukemia; design, synthesis and evaluation of novel formulations of oligonucleotides, including antisense oligos and siRNA, receptor-based imaging contrast agents; non-viral vectors for gene therapy; nanocarriers for neutron capture therapy; liposome and nanoparticle-based drug carriers; targeted immunotherapeutic anticancer strategies.
Human bodies have many molecular motors and machines [1]. In these biomotors, nature demonstrates... more Human bodies have many molecular motors and machines [1]. In these biomotors, nature demonstrates most elegantly that simple molecular mechanical components, once organized and assembled in a precise manner, can link motions efficiently from the nanometer scale to the macroscopic world, and achieve complex functions such as powering skeletal muscles, synthesizing ATP (the energy source for most living creatures), and producing DNA/RNA (the origin of life).
We establish the role of tether conductivity in the photoisomerization of azobenzene-functionaliz... more We establish the role of tether conductivity in the photoisomerization of azobenzene-functionalized molecules assembled as isolated single molecules in well-defined decanethiolate self-assembled monolayer (SAM) matrices on Au {111}. We designed the molecules so as to tune the conductivity of the tethers that separate the functional moiety from the underlying Au substrate.
We have fabricated aminopropyltriethoxysilane (APTES)-functionalized nanoporous polymeric grating... more We have fabricated aminopropyltriethoxysilane (APTES)-functionalized nanoporous polymeric gratings by combining holographic interference patterning and APTES-functionalization of the pre-polymer syrup. The APTES facilitates the immobilization of biomolecules onto the polymeric grating surfaces.
We identify and control the photoreaction paths of self-assembled monolayers (SAMs) of thiolate-l... more We identify and control the photoreaction paths of self-assembled monolayers (SAMs) of thiolate-linked anthracene phenylethynyl molecules on Au substrate surfaces, and study the effects of nanoscale morphology of substrates on regioselective photoreactions. Two types of morphologies–atomically flat and curved–are produced on Au surfaces by controlling substrate structure and metal deposition.
Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such a... more Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons.
Silver nanowire (AgNW) networks are promising candidates to replace indiumÀtinÀoxide (ITO) as tra... more Silver nanowire (AgNW) networks are promising candidates to replace indiumÀtinÀoxide (ITO) as transparent conductors. However, complicated treatments are often required to fuse crossed AgNWs to achieve low resistance and good substrate adhesion. In this work, we demonstrate a simple and effective solution method to achieve highly conductive AgNW composite films with excellent optical transparency and mechanical properties. These properties are achieved via sequentially applying TiO 2 solÀgel and PEDOT:PSS solution to treat the AgNW film. TiO 2 solution volume shrinkage and the capillary force induced by solvent evaporation result in tighter contact between crossed AgNWs and improved film conductivity.
A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when expos... more A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when exposed to chemical oxidants and reductants, undergoes switching of its plasmonic properties reversibly. By contrast, (i) bare gold nanodisks and (ii) disks coated with a redox-active, but mechanically inert, control compound do not display surface-plasmon-based switching. Along with calculations based on time-dependent density functional theory, these experimental observations suggest that the nanoscale movements within surface-bound "molecular machines" can be used as the active components in plasmonic devices.
Abstract By combining two self-organized templates, the authors fabricate hierarchically ordered ... more Abstract By combining two self-organized templates, the authors fabricate hierarchically ordered nanowire arrays on substrates. The nanowire arrays consist of periodic voids at the microscale and hexagonally packed nanowires at the nanoscale. The nanowires are created by selective electrodeposition using nanoporous anodic alumina as a template and a porous gold film as a working electrode that is patterned by microsphere monolayers. In addition to in-plane hierarchical structure, they have sequentially varied the vertical ...
In this work the influence of geometry and composition on the charge-induced plasmonic shifts (CI... more In this work the influence of geometry and composition on the charge-induced plasmonic shifts (CIPS) of gold nanoparticles are systematically studied using Mie scattering theory and the discrete dipole approximation. The sensitivity of nanorods and nanodisks with different aspect ratio and nanoshells with different volume fractions and compositions are studied using different charging levels. The electrodynamics calculations were performed by changing the internal electron density in the Drude model for the dielectric constant of gold. We show that, for a constant volume, nanodisks and nanorods exhibit CIPS with a linear dependence on aspect ratio. Geometries having higher aspect ratio show larger CIPS. In nanoshells, increasing the volume fraction of the core causes a slow increase of CIPS at first followed by a rapid increase for larger volume fractions. In addition, we find that nanoshells with the same volume fractions exhibit larger shifts when the refractive index of the cores is larger. Furthermore, the electrodynamics results are interpreted using analytical approximations based on quasistatic theory. The qualitative understanding of geometric and composition effects on the CIPS of gold nanoparticles obtained in this work can hopefully be used to realize highly tunable charge-based active plasmonic devices.
We report a holographically fabricated, optically switchable grating using azo-dye-doped, polymer... more We report a holographically fabricated, optically switchable grating using azo-dye-doped, polymer-dispersed liquid crystals (LCs). Our experiments show that upon photoirradiation, the diffraction of the grating was decreased significantly. We believe that this switching behavior is due to two factors-nematic-isotropic phase transition of LCs and thermal expansion of the grating structure.
In this work, we show using both experiments and classical electrodynamic simulations that plasmo... more In this work, we show using both experiments and classical electrodynamic simulations that plasmon splitting in resonant molecule-coated nanoparticles increases linearly as the square root of absorbance of the molecular layer. This linear relationship shows the same universal behavior established in analogous systems such as cavity-polariton and surface plasmon polariton systems. To explain this behavior, a simple physical mechanism based on linear dispersion and absorption is proposed. The insights obtained in this study can be used as a general principle for designing resonant molecule-coated nanoparticles for realizing tunable nanophotonic devices and molecular sensing.
A nanoporous polymer thin film has been developed as a potential platform for drug delivery. The ... more A nanoporous polymer thin film has been developed as a potential platform for drug delivery. The film was fabricated by a light-induced polymerization process in which non-reactive solvent was first separated from photopolymer (dipentaerythritol penta-/hexa-acrylate as the monomer) and then removed from polymer via evaporation, yielding pores with diameters between 20 and 40 nm. Loading and release of Rhodamine B (drug model molecules) on both porous and non-porous thin films proved that nanopores enhanced the film's effectiveness in encapsulating and releasing the drug model molecules, which was attributed to the high surface-to-volume ratio of nanoporous film. Ultrasound-enhanced cumulative and pulsatile release revealed the advantages of ultrasound in controlled drug delivery.
Development of targeted drug delivery systems for cancer and leukemia; design, synthesis and eval... more Development of targeted drug delivery systems for cancer and leukemia; design, synthesis and evaluation of novel formulations of oligonucleotides, including antisense oligos and siRNA, receptor-based imaging contrast agents; non-viral vectors for gene therapy; nanocarriers for neutron capture therapy; liposome and nanoparticle-based drug carriers; targeted immunotherapeutic anticancer strategies.
Human bodies have many molecular motors and machines [1]. In these biomotors, nature demonstrates... more Human bodies have many molecular motors and machines [1]. In these biomotors, nature demonstrates most elegantly that simple molecular mechanical components, once organized and assembled in a precise manner, can link motions efficiently from the nanometer scale to the macroscopic world, and achieve complex functions such as powering skeletal muscles, synthesizing ATP (the energy source for most living creatures), and producing DNA/RNA (the origin of life).
We establish the role of tether conductivity in the photoisomerization of azobenzene-functionaliz... more We establish the role of tether conductivity in the photoisomerization of azobenzene-functionalized molecules assembled as isolated single molecules in well-defined decanethiolate self-assembled monolayer (SAM) matrices on Au {111}. We designed the molecules so as to tune the conductivity of the tethers that separate the functional moiety from the underlying Au substrate.
We have fabricated aminopropyltriethoxysilane (APTES)-functionalized nanoporous polymeric grating... more We have fabricated aminopropyltriethoxysilane (APTES)-functionalized nanoporous polymeric gratings by combining holographic interference patterning and APTES-functionalization of the pre-polymer syrup. The APTES facilitates the immobilization of biomolecules onto the polymeric grating surfaces.
We identify and control the photoreaction paths of self-assembled monolayers (SAMs) of thiolate-l... more We identify and control the photoreaction paths of self-assembled monolayers (SAMs) of thiolate-linked anthracene phenylethynyl molecules on Au substrate surfaces, and study the effects of nanoscale morphology of substrates on regioselective photoreactions. Two types of morphologies–atomically flat and curved–are produced on Au surfaces by controlling substrate structure and metal deposition.
Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such a... more Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons.
Silver nanowire (AgNW) networks are promising candidates to replace indiumÀtinÀoxide (ITO) as tra... more Silver nanowire (AgNW) networks are promising candidates to replace indiumÀtinÀoxide (ITO) as transparent conductors. However, complicated treatments are often required to fuse crossed AgNWs to achieve low resistance and good substrate adhesion. In this work, we demonstrate a simple and effective solution method to achieve highly conductive AgNW composite films with excellent optical transparency and mechanical properties. These properties are achieved via sequentially applying TiO 2 solÀgel and PEDOT:PSS solution to treat the AgNW film. TiO 2 solution volume shrinkage and the capillary force induced by solvent evaporation result in tighter contact between crossed AgNWs and improved film conductivity.
A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when expos... more A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when exposed to chemical oxidants and reductants, undergoes switching of its plasmonic properties reversibly. By contrast, (i) bare gold nanodisks and (ii) disks coated with a redox-active, but mechanically inert, control compound do not display surface-plasmon-based switching. Along with calculations based on time-dependent density functional theory, these experimental observations suggest that the nanoscale movements within surface-bound "molecular machines" can be used as the active components in plasmonic devices.
Abstract By combining two self-organized templates, the authors fabricate hierarchically ordered ... more Abstract By combining two self-organized templates, the authors fabricate hierarchically ordered nanowire arrays on substrates. The nanowire arrays consist of periodic voids at the microscale and hexagonally packed nanowires at the nanoscale. The nanowires are created by selective electrodeposition using nanoporous anodic alumina as a template and a porous gold film as a working electrode that is patterned by microsphere monolayers. In addition to in-plane hierarchical structure, they have sequentially varied the vertical ...
In this work the influence of geometry and composition on the charge-induced plasmonic shifts (CI... more In this work the influence of geometry and composition on the charge-induced plasmonic shifts (CIPS) of gold nanoparticles are systematically studied using Mie scattering theory and the discrete dipole approximation. The sensitivity of nanorods and nanodisks with different aspect ratio and nanoshells with different volume fractions and compositions are studied using different charging levels. The electrodynamics calculations were performed by changing the internal electron density in the Drude model for the dielectric constant of gold. We show that, for a constant volume, nanodisks and nanorods exhibit CIPS with a linear dependence on aspect ratio. Geometries having higher aspect ratio show larger CIPS. In nanoshells, increasing the volume fraction of the core causes a slow increase of CIPS at first followed by a rapid increase for larger volume fractions. In addition, we find that nanoshells with the same volume fractions exhibit larger shifts when the refractive index of the cores is larger. Furthermore, the electrodynamics results are interpreted using analytical approximations based on quasistatic theory. The qualitative understanding of geometric and composition effects on the CIPS of gold nanoparticles obtained in this work can hopefully be used to realize highly tunable charge-based active plasmonic devices.
We report a holographically fabricated, optically switchable grating using azo-dye-doped, polymer... more We report a holographically fabricated, optically switchable grating using azo-dye-doped, polymer-dispersed liquid crystals (LCs). Our experiments show that upon photoirradiation, the diffraction of the grating was decreased significantly. We believe that this switching behavior is due to two factors-nematic-isotropic phase transition of LCs and thermal expansion of the grating structure.
In this work, we show using both experiments and classical electrodynamic simulations that plasmo... more In this work, we show using both experiments and classical electrodynamic simulations that plasmon splitting in resonant molecule-coated nanoparticles increases linearly as the square root of absorbance of the molecular layer. This linear relationship shows the same universal behavior established in analogous systems such as cavity-polariton and surface plasmon polariton systems. To explain this behavior, a simple physical mechanism based on linear dispersion and absorption is proposed. The insights obtained in this study can be used as a general principle for designing resonant molecule-coated nanoparticles for realizing tunable nanophotonic devices and molecular sensing.
A nanoporous polymer thin film has been developed as a potential platform for drug delivery. The ... more A nanoporous polymer thin film has been developed as a potential platform for drug delivery. The film was fabricated by a light-induced polymerization process in which non-reactive solvent was first separated from photopolymer (dipentaerythritol penta-/hexa-acrylate as the monomer) and then removed from polymer via evaporation, yielding pores with diameters between 20 and 40 nm. Loading and release of Rhodamine B (drug model molecules) on both porous and non-porous thin films proved that nanopores enhanced the film's effectiveness in encapsulating and releasing the drug model molecules, which was attributed to the high surface-to-volume ratio of nanoporous film. Ultrasound-enhanced cumulative and pulsatile release revealed the advantages of ultrasound in controlled drug delivery.
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Papers by Yuebing Zheng