Amino-modified TiO₂ Nanoparticles Conjugated with Sulfonated Aluminum Phthalocyanine for Improvement of Photodynamic Therapy

Xiaobo Pan

Supervisor: Pei-nan Wang, Lan Mi

Photodynamic therapy (PDT), as a new cancer therapy, has been attracted increasing attention [1-4]. Semiconductor titanium dioxide (TiO₂) was noticed as a potential photosensitizer due to its low toxicity, high chemical stability, good photoreactivity and excellent biocompatibility. However, TiO₂ can only be activated by UV light and aggregate easily in water, which hinders its application and development in PDT. In 2011, we prepared nitrogen-doped titania (N-TiO₂) by calcinations to expand titania absorption spectrum from UV to the visible region[5].

In this work, to enhance titania in aqueous solution, amino-modified TiO₂ and N-TiO₂ nanoparticles (TiO₂-NH₂) was prepared, which charged positively and greatly enhanced dispersibility in water. The cellular uptake of TiO₂-NH₂ was more effectively than that of bare TiO₂ according to the observation by scanning transmission X-ray microscopy.

Sulfonated aluminum phthalocynaine (AlPcS4), as a photosensitiser, has been officially approved in clinical PDT[6]. To utilize red light (its wavelength is within the “optical window” of human body) applied in PDT, Pc- TiO₂ composite was prepared by mixing negatively charged AlPcS₄) molecules with positively charged TiO₂-NH₂ solution, which can be effectively bound due to electrostatic attraction. It was investigated that Pc- TiO₂ can enter cells more efficiently than free Pc. No significant toxicity was detected after 24 hours incubation with cells. Moreover, more cells were killed by the conjugates than free Pc with irradiation by a red light source, as well as a broad-band visible light source. Furthermore, Pc-N-TiO₂ was prepared by the same method using AlPcS₄ and N-TiO₂ as the reactants. Under both red-light and broad-band visible irradiation, the photokilling effect of Pc-N-TiO₂ was greatly enhanced than that of Pc-TiO_2.

参考文献:

[1] Hackbarth S, Schlothauer J, Preuß A, Röder B (2010) New insights to primary photodynamic effects – Singlet oxygen kinetics in living cells. Journal of Photochemistry and Photobiology B: Biology 98:173-179

[2] Lei W, Zhou Q, Li Z, Wang X, Zhang B (2009) Photodynamic Activity of Ascorbic Acid-modified TiO2 Nanoparticles upon Visible Illumination (>550 nm). Chemistry Letters 38:1138-1139

[3] Lai T-Y, Lee W-C (2009) Killing of cancer cell line by photoexcitation of folic acid-modified titanium dioxide nanoparticles. Journal of Photochemistry and Photobiology A: Chemistry 204:148-153

[4] Vanderesse R, Frochot C, Barberi-Heyob M, Richeter S, Raehm L, Durand J-O (2011) Nanoparticles for Photodynamic Therapy Applications.  5:511-565

[5] Li Z, Mi L, Wang P-N, Chen J-Y (2011) Study on the visible-light-induced photokilling effect of nitrogen-doped TiO2 nanoparticles on cancer cells. Nanoscale Res Lett 6:1-7

[6] Tamietti BFP, Machado AHA, Maftoum-Costa M, Da Silva NS, Tedesco AC, Pacheco-Soares C (2007) Analysis of Mitochondrial Activity Related to Cell Death after PDT with AlPCS4. Photomedicine and Laser Surgery 25:175-179

Black Silicon and First Principle Calculation

Zhen Zhu

Supervisor: Jun Zhuang

Black silicon has become a kind of material of increasing importance because of its various novel properties in optics and electronics. Recently, carrier lifetime recovery with increasing doping concentration was found in Ti-doped black silicon, and insulator-to-metal (IMT) transition was found in S, Se, and Ti -doped black silicon in succession. Certainly, the most well-known properties are the significant enhancement of photocurrent generation and broadband absorption of black silicon doped with chalcogens (S, Se, Te). These properties make black silicon a promising material in photovoltaic and photoelectricity field. The samples can be obtained by different methods, including pulse laser irradiation on silicon surfaces with impurity-containing gas atmosphere or with dopant powder spreading on the surface, ion implantation followed by pulse laser melting technique, etc. By these methods the dopant concentration in silicon can exceed its limit of solid solution by several magnitudes.

We model various kinds of dopant structures and use first principle calculation to investigate the dopant structure formation, electronic structure, optics constant, mechanism of IMT, etc. The results of electronic structures show that in various dopant structures, the doped atom can introduce impurity bands into the band-gap of silicon, which induce sub-band-gap absorption of radiation. By molecular-dynamics (MD) calculations, we found that some dopant structures will transform in high temperature, which could explain the instability of sulfur-doped black silicon in annealing process. IMT process is disclosed to be not relative to the merging between impurity band and conduction band, which promises high efficiency intermediate band photovoltaics (IBPV) to be possible. Our recent work is concentrated on nitrogen-doped black silicon, which possesses good crystallinity, strong mid-IR absorption, and thermal stability.

参考文献:

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SPDT turning of KDP crystal

 Lianliang Liu

Supervisor:Min Xu

In large laser system such as NIF, KDP (potassium dihydrogen phosphate) crystal is used in the plasma electrode pockels cell (PEPC) and frequency doubling crystals, while deuterated KDP (DKDP) crystals are used for frequency tripling. China also choose KDP crystal as frequency optics in ShenGuang facility because of its relative high frequency efficiency and easy to produce. Large laser system such as NIF (National Ignition Facility) is built to focus hundreds of laser beams on a target to get a high temperature and high pressure.

Methods for reproducible growth of single crystals of KDP that meet all material requirements have been developed that enable us to meet the optics demands of the NIF.  Once material properties are met, fabrication of high aspect ratio single crystal optics (42×42×1 cm) to meet laser performance specifications is the next challenge. This report will talk about the material properties of Chinese KDP crystal and then show our fabrication method. A few problems in fabrication, for example, vacuum chuck, turning tools, cutting depth and cleaning methods will be discussed. 

参考文献：

[1] J. H. Campbell et.al, NIF optical materials and fabrication technologies: An overview, Proceedings of SPIE Vol.5341(2004)

[2] R. Hawley-Fedder*, P. Geraghty, S. Locke, M. McBurney, NIF Pockels Cell and Frequency Conversion Crystals, Proceedings of SPIE Vol.5341(2004)

[3] R. C. Montesanti S. L. Thompson, A Procedure for Diamond Turning KDP Crystals, UCRL-ID-121651 ,LLNL (1995)

[4] Philippe LAHAYE, Christian CHOMONT, Pierre DUMONT, Using a Design of Experiment method to improve KDP crystals machining process, SPIE Vol. 3492

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