Preparation and near-infrared photothermal conversion property of cesium tungsten oxide nanoparticles
© Chen and Chen; licensee Springer. 2013
Received: 21 December 2012
Accepted: 18 January 2013
Published: 5 February 2013
Cs0.33WO3 nanoparticles have been prepared successfully by a stirred bead milling process. By grinding micro-sized coarse powder with grinding beads of 50 μm in diameter, the mean hydrodynamic diameter of Cs0.33WO3 powder could be reduced to about 50 nm in 3 h, and a stable aqueous dispersion could be obtained at pH 8 via electrostatic repulsion mechanism. After grinding, the resulting Cs0.33WO3 nanoparticles retained the hexagonal structure and had no significant contaminants from grinding beads. Furthermore, they exhibited a strong characteristic absorption and an excellent photothermal conversion property in the near-infrared (NIR) region, owing to the free electrons or polarons. Also, the NIR absorption and photothermal conversion property became more significant with decreasing particle size or increasing particle concentration. When the concentration of Cs0.33WO3 nanoparticles was 0.08 wt.%, the solution temperature had a significant increase of above 30°C in 10 min under NIR irradiation (808 nm, 2.47 W/cm2). In addition, they had a photothermal conversion efficiency of about 73% and possessed excellent photothermal stability. Such an effective NIR absorption and photothermal conversion nanomaterial not only was useful in the NIR shielding, but also might find great potential in biomedical application.
KeywordsCesium tungsten oxide Nanoparticles Near infrared Photothermal conversion Bead milling
Plasmonic nanomaterials could exhibit special absorption via the excitation of surface plasmon [1–3], and the maximum absorption band was highly sensitive to the particle’s size [4, 5], shape , local environment , and the coupling between near nanoparticles . Furthermore, under optical illumination, they could convert the absorbed photon energy into heat energy in approximately 1 ps and then transfer the heat to the surrounding media in tens of picoseconds [2–4, 9]. Such an efficient light-to-heat conversion property made them become useful as nanoheaters and therefore gain more and more attention in the past decade [1, 9].
Photothermal therapy is an attractive therapy technique using photosensitizers to generate heat from light absorption and then kill the cancer cells [10, 11]. To avoid the nonspecific heating of healthy cells and allow deeper penetration into tissues, near-infrared (NIR) light is usually utilized . Furthermore, because the use of plasmonic nanomaterials as photosensitizers makes this technique possess spatial selectivity, a lot of plasmonic nanomaterials with NIR photothermal conversion property have been examined. Typical examples include gold nanorods [13–15], gold nanoshells [16, 17], gold nanocages , single-walled [19–21] or multi-walled  carbon nanotubes, graphene or reduced graphene oxide , and germanium . Among them, gold-based nanomaterials received the most attention, owing to their good biocompatibility and tunable optical property. However, gold is an expensive noble metal, and the preparation of its nanostructures with NIR photothermal conversion property usually needs an accurate synthesis condition or repeated deposition. Thus, the alternatives with lower cost or simpler preparation method are still in demand .
Recently, to reduce the energy consumption for air-conditioning and decrease the emission of carbon dioxide, NIR-shielding materials have received considerable attention in the development of transparent and solar heat-shielding filters for solar control windows of automobiles and architectures [26–34]. Among various materials with the capability of shielding NIR light via reflection or absorption mechanism, cesium tungsten oxide (particularly Cs0.33WO3) nanoparticles have been regarded to be highly promising in transparent solar filter application [26–30]. Because of the strong absorption in the NIR region, owing to the free electrons or polars, they also might be efficient as a photosensitizer in NIR photothermal therapy. However, their utilization in heating the reaction media or photothermal therapy via NIR photothermal conversion has not been reported.
Until now, only limited work has been reported for the solvothermal synthesis of cesium tungsten oxide nanorods . The main method for the synthesis of cesium tungsten oxides was the solid state reaction . To obtain the nanosized powder, further grinding was necessary. Thus, in this work, Cs0.33WO3 nanoparticles were prepared by a stirred bead milling process. Although Takeda and Adachi have reported the preparation of tungsten oxide nanoparticles by milling in organic medium with a dispersant agent , for future possible biomedical application and avoiding the use of toxic organic solvent, an aqueous milling process of Cs0.33WO3 nanoparticles without extra dispersant agents which have not been reported was attempted in this work. The appropriate pH of dispersion solution for grinding was determined, and the effect of grinding time on the size of Cs0.33WO3 nanoparticles was examined. Furthermore, the NIR photothermal conversion property of the resulting Cs0.33WO3 powder after grinding for various times was studied to demonstrate the excellent NIR photothermal conversion property of Cs0.33WO3 nanoparticles.
Cesium tungsten oxide (Cs0.33WO3) coarse powder with a primary particle size of about 1 to 2 μm were obtained from the Industrial Technology Research Institute of Taiwan (ITRI). Deionized water was produced by Direct-Q3 ultrapure water system of Millipore Co., Billerica, MA, USA. Potassium hydroxide was purchased from Wako Pure Chemical Industry Co., Ltd (Osaka, Japan). Nitric acid was supplied by Merck KGaA (Darmstadt, Germany). The yttrium-stabilized zirconia (95% ZrO2, 5% Y2O3; density 6,060 kg/m3) grinding beads with a diameter of 50 μm were obtained from Toray Ind., Inc. (Tokyo, Japan). Polyethylene glycol 6000 (PEG 6000; molecular weight 7,000 to approximately 9,000 daltons) was a product of Merck KGaA.
Cs0.33WO3 nanoparticles were prepared via a stirred bead milling process using high-performance batch-type stirred bead mill JBM-B035 manufactured by Just Nanotech Co., Ltd, Tainan, Taiwan. This mill consists of a rotor, a mill chamber, and grinding beads. The rotor and mill chamber are made of highly wear-resistant materials: sintered silicon carbide. The mill chamber is cooled with water and has a net grinding charmer volume of 350 mL. The grinding beads are fluidized by the rotor in the mill chamber as the grinding medium. For the typical stirred bead milling process, Cs0.33WO3 coarse powder (10 wt.%) was added to the aqueous solution of potassium hydroxide at pH 8, and then the dispersion was put into the stirred bead mill. An agitation speed of 2,400 rpm (peripheral speed 10 m/s) was used to exert both shearing and imparting forces on the Cs0.33WO3 coarse powder and was run for different times. Samples were taken at various intervals of grinding time for particle size analysis. The filling ratio of the mill chambers by grinding beads was 60 vol.%. The mill was operated at a constant temperature of 20°C.
The zeta potential and mean hydrodynamic diameter of Cs0.33WO3 nanoparticles in the aqueous dispersion were measured using a Malvern Nano-ZS dynamic light-scattering spectrometer (Malvern Instruments Ltd., Worcestershire, UK). For the measurement of zeta potential, the concentration of Cs0.33WO3 nanoparticles was 10 mg/L, and the pH of aqueous dispersion was adjusted by the addition of potassium hydroxide or nitric acid. Transmission electron microscopy (TEM) analysis was carried out on a Hitachi model H-7500 (Hitachi High-Tech, Minato-ku, Tokyo, Japan) at 120 kV. High-resolution TEM (HRTEM) image of a single Cs0.33WO3 nanoparticle and the corresponding electron diffraction pattern were observed using a Jeol model JEM-2100F (JEOL Ltd., Akishima, Tokyo, Japan) at 200 kV. The content of the contaminant ZrO2 from the stirred bead milling process was determined using an energy dispersive X-ray (EDX) spectrometer attached to the TEM. The crystal structure was characterized by X-ray diffraction (XRD) analysis on a Shimadzu RX-III X-ray diffractometer (Shimadzu Corporation, Nakagyo-ku, Kyoto, Japan) using CuKα radiation (λ = 0.1542 nm). The absorption spectra were measured by a Jasco V-570 UV–vis-NIR spectrophotometer (Jasco Analytical Instruments, Eaton, MD, USA).
The NIR photothermal conversion property of Cs0.33WO3 nanoparticles was investigated in deionized water at different concentrations. The aqueous dispersion of Cs0.33WO3 nanoparticles was added to a 2-mL polystyrene cell, and then the dispersion was exposed to an 808-nm diode laser (HPM (LD1202) X26, Power Technology Inc., Little Rock, AR, USA) with an irradiation area of 0.3 cm2 and an intensity of 820 mW (i.e., 2.73 W/cm2). The temperature of aqueous dispersion was detected with a thermocouple. Photothermal conversion efficiency was calculated using the method reported by Chen et al. . For the study on the photothermal stability of Cs0.33WO3 nanoparticles under NIR irradiation, the aqueous dispersion of Cs0.33WO3 nanoparticles (0.08 wt.%, obtained after grinding for 3 h) was continuously re-exposed to an 808-nm diode laser (2.73 W/cm2) for 5 cycles. For each cycle, the aqueous dispersion was irradiated for 10 min and then cooled to the initial temperature. Using a thermocouple, the variation of temperature with time was monitored.
Results and discussion
According to the method reported by Chen et al. , the photothermal conversion efficiency for the aqueous dispersion of Cs0.33WO3 nanoparticles (2 mg/mL) under NIR irradiation (808 nm, 2.47 mW/cm2) could be determined to be 73%, close to that of gold nanorods with an effective radius of 30 nm. Because the Cs0.33WO3 nanoparticles examined had a mean hydrodynamic diameter of 50 nm and the photothermal conversion efficiency increased with the decrease of particle size , this result revealed that the resulting Cs0.33WO3 nanoparticles had a photothermal conversion property comparable to gold nanorods.
Hexagonal Cs0.33WO3 nanoparticles with a mean hydrodynamic diameter of about 50 nm were prepared successfully in an aqueous solution of pH 8 by bead milling. They possessed excellent NIR photothermal conversion property and stability. With decreasing particle size or increasing particle concentration, the NIR photothermal conversion-induced temperature increase is enhanced. Such a nanomaterial not only could be used in the transparent solar heat-shielding filters, but also is useful for the development of NIR-triggered photothermal conversion materials in biomedicine.
CJC is currently a Ph.D. student of the National Cheng Kung University (Taiwan). DHC is a distinguished professor of the Chemical Engineering Department at National Cheng Kung University (Taiwan).
We are grateful to the National Science Council, Taiwan, for the support of this research under contract no. NSC 100-2221-E-006-164-MY2.
- Huang W, EI-Sayed MA: Photothermally excited coherent lattice phonon oscillations in plasmonic nanoparticles. Eur Phys J Special Topics 2008, 153: 325–333. 10.1140/epjst/e2008-00456-xView ArticleGoogle Scholar
- Link S, Burda C, Nikoobakht B, EI-Sayed MA: How long does it take to melt a gold nanorod? A femtosecond pump–probe absorption spectroscopic study. Chem Phys Lett 1999, 315: 12–18. 10.1016/S0009-2614(99)01214-2View ArticleGoogle Scholar
- Link S, EI-Sayed MA: Optical properties and ultrafast dynamics of metallic nanocrystals. Ann Rev Phys Chem 2003, 54: 331–366. 10.1146/annurev.physchem.54.011002.103759View ArticleGoogle Scholar
- Link S, EI-Sayed MA: Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods. J Phys Chem B 1999, 103: 8410–8426. 10.1021/jp9917648View ArticleGoogle Scholar
- Jensen TR, Malinsky MD, Haynes CL, Van Duyne RP: Nanosphere lithography: tunable localized surface plasmon resonance spectra of silver nanoparticles. J Phys Chem B 2000, 104: 10549–10556. 10.1021/jp002435eView ArticleGoogle Scholar
- Link S, EI-Sayed MA: Shape and size dependence of radiative, non-radiative and photothermal properties of gold nanocrystals. Int Rev Phys Chem 2000, 19: 409–453. 10.1080/01442350050034180View ArticleGoogle Scholar
- Haes AJ, Van Dutne RP: A nanoscale optical biosensor: sensitivity and selectivity of an approach based on the localized surface plasmon resonance spectroscopy of triangular silver nanoparticles. J Am Chem Soc 2002, 124: 10596–10604. 10.1021/ja020393xView ArticleGoogle Scholar
- Haynes CL, McFarland AD, Zhao LL, Van Duyne RP, Schatez GC, Gunnarsson L, Prikulis J, Kasemo B, Kall M: Nanoparticle optics: the importance of radiative dipole coupling in two-dimensional nanoparticle arrays. J Phys Chem B 2003, 107: 7337–7342.View ArticleGoogle Scholar
- Richardson HH, Carlson MT, Tandler PJ, Hernandez P, Govorov AO: Experimental and theoretical studies of light-to-heat conversion and collective heating effects in metal nanoparticle solutions. Nano Lett 2009, 9: 1139–1146. 10.1021/nl8036905View ArticleGoogle Scholar
- Kam W, O’Connell M, Wisdom JA, Dai H: Carbon nanotubes as multifunctional biological transporters and near-infrared agents for selective cancer cell destruction. Proc Natl Acad Sci USA 2005, 102: 11600–11605. 10.1073/pnas.0502680102View ArticleGoogle Scholar
- Ye E, Yin K, Tan HR, Lin M, Teng CP, Mlayah A, Han MY: Plasmonic gold nanocrosses with multidirectional excitation and strong photothermal effect. J Am Chem Soc 2011, 133: 8506–8509. 10.1021/ja202832rView ArticleGoogle Scholar
- Welsher K, Liu Z, Sherlock SP, Robinson JT, Chen Z, Daranciang D, Dai H: A route to brightly fluorescent carbon nanotubes for near-infrared imaging in mice. Nat Nanotechnol 2009, 4: 773–780. 10.1038/nnano.2009.294View ArticleGoogle Scholar
- Huang X, El-Sayed IH, Qian W, El-Sayed MA: Cancer cell imaging and photothermal therapy in the near-infrared region by using gold nanorods. J Am Chem Soc 2006, 128: 2115–2120. 10.1021/ja057254aView ArticleGoogle Scholar
- Huang HC, Barua S, Kay DB, Rege K: Simultaneous enhancement of photothermal stability and gene delivery efficacy of gold nanorods using polyelectrolytes. ACS Nano 2009, 3: 2941–2952. 10.1021/nn900947aView ArticleGoogle Scholar
- Zhang Z, Wang L, Wang J, Jiang X, Li X, Hu Z, Ji Y, Wu X, Chen C: Mesoporous silica-coated gold nanorods as a light-mediated multifunctional theranostic platform for cancer treatment. Adv Mater 2012, 24: 1418–1423. 10.1002/adma.201104714View ArticleGoogle Scholar
- Hirsch LR, Stafford RJ, Bankson JA, Sershen SR, Rivera B, Price RE, Hazle JD, Halas NJ, West JL: Nanoshell-mediated near-infrared thermal therapy of tumors under magnetic resonance guidance. Proc Natl Acad Sci USA 2003, 100: 13549–13554. 10.1073/pnas.2232479100View ArticleGoogle Scholar
- Dong W, Li Y, Niu D, Ma Z, Gu J, Chen Y, Zhao W, Liu X, Liu C, Shi J: Facile synthesis of monodisperse superparamagnetic Fe3O4 core@hybrid@Au shell nanocomposite for bimodal imaging and photothermal therapy. Adv Mater 2011, 23: 5392–5397. 10.1002/adma.201103521View ArticleGoogle Scholar
- Chen J, Wang D, Xi J, Au L, Siekkinen A, Warsen A, Li ZY, Zhang H, Xia Y, Li X: Immuno gold nanocages with tailored optical properties for targeted photothermal destruction of cancer cells. Nano Lett 2007, 7: 1318–1322. 10.1021/nl070345gView ArticleGoogle Scholar
- Zhou F, Wu S, Song S, Chen WR, Resasco DE, Xing D: Antitumor immunologically modified carbon nanotubes for photothermal therapy. Biomaterials 2012, 33: 3235–3342. 10.1016/j.biomaterials.2011.12.029View ArticleGoogle Scholar
- Markovic ZM, Harhaji-Trajkovic LM, Todorovic-Markovic BM, Kepić DP, Arsikin KM, Jovanović SP, Pantovic AC, Draićanin MD, Trajkovic VS: In vitro comparison of the photothermal anticancer activity of graphene nanoparticles and carbon nanotubes. Biomaterials 2011, 32: 1121–1129. 10.1016/j.biomaterials.2010.10.030View ArticleGoogle Scholar
- Liu X, Tao H, Yang K, Zhang S, Lee ST, Liu Z: Optimization of surface chemistry on single-walled carbon nanotubes for in vivo photothermal ablation of tumors. Biomaterials 2011, 32: 144–151. 10.1016/j.biomaterials.2010.08.096View ArticleGoogle Scholar
- Fisher JW, Sarkar S, Buchanan CF, Szot CS, Whitney J, Hatcher HC, Torti SV, Rylander CG, Rylander MN: Photothermal response of human and murine cancer cells to multiwalled carbon nanotubes after laser irradiation. Cancer Res 2010, 70: 9855–9864. 10.1158/0008-5472.CAN-10-0250View ArticleGoogle Scholar
- Robinson JT, Tabakman SM, Liang Y, Wang H, Casalongue HS, Vinh D, Dai H: Ultrasmall reduced graphene oxide with high near-infrared absorbance for photothermal therapy. J Am Chem Soc 2011, 133: 6825–6831. 10.1021/ja2010175View ArticleGoogle Scholar
- Lambert TN, Andrews NL, Gerung H, Boyle TJ, Oliver JM, Wilson BS, Han SM: Water-soluble germanium(0) nanocrystals: cell recognition and near-infrared photothermal conversion properties. Small 2007, 3: 691–699. 10.1002/smll.200600529View ArticleGoogle Scholar
- Chen CJ, Chen DH: Preparation of LaB6 nanoparticles as a novel and effective near-infrared photothermal conversion material. Chem Eng J 2012, 180: 337–342.View ArticleGoogle Scholar
- Liu JX, Ando Y, Dong XL, Shi F, Yin S, Adachi K, Chonan T, Tanaka A, Sato T: Microstructure and electrical–optical properties of cesium tungsten oxides synthesized by solvothermal reaction followed by ammonia annealing. J Solid State Chem 2010, 183: 2456–2460. 10.1016/j.jssc.2010.08.017View ArticleGoogle Scholar
- Guo C, Yin S, Yan M, Sato T: Facile synthesis of homogeneous CsxWO3 nanorods with excellent low-emissivity and NIR shielding property by a water controlled-release process. J Mater Chem 2011, 21: 5099–5105. 10.1039/c0jm04379fView ArticleGoogle Scholar
- Takeda H, Adachi K: Near infrared absorption of tungsten oxide nanoparticle dispersions. J Am Ceram Soc 2007, 90: 4059–4061.Google Scholar
- Liu J, Wang X, Shi F, Peng Z, Luo J, Xu Q, Du P: Hydrothermal synthesis of cesium tungsten bronze and its heat insulation properties. Adv Mater Res 2012, 531: 235–239.View ArticleGoogle Scholar
- Guo C, Yin S, Huang L, Yang L, Sato T: Discovery of an excellent IR absorbent with a broad working waveband: CsxWO3 nanorods. Chem Commun 2011, 47: 8853–8855. 10.1039/c1cc12711jView ArticleGoogle Scholar
- Guo C, Yin S, Huang L, Sato T: Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property. ACS Appl Mater Interfaces 2011, 3: 2794–2799. 10.1021/am200631eView ArticleGoogle Scholar
- Guo C, Yin S, Huang Y, Dong Q, Sato T: Synthesis of W18O49 nanorod via ammonium tungsten oxide and its interesting optical properties. Langmuir 2011, 27: 12172–12178. 10.1021/la202513qView ArticleGoogle Scholar
- Guo C, Yin S, Yan M, Kobayashi M, Kakihana M, Sato T: Morphology-controlled synthesis of W18O49 nanostructures and their near-infrared absorption properties. Inorg Chem 2012, 51: 4763–4771. 10.1021/ic300049jView ArticleGoogle Scholar
- Guo C, Yin S, Dong Q, Sato T: Simple route to (NH4)xWO3 nanorods for near infrared absorption. Nanoscale 2012, 4: 3394. 10.1039/c2nr30612cView ArticleGoogle Scholar
- Chen HJ, Shao L, Ming T, Sun ZH, Zhao CM, Yang BC, Wang JF: Understanding the photothermal conversion efficiency of gold nanocrystals. Small 2010, 6: 2272–2280. 10.1002/smll.201001109View ArticleGoogle Scholar
- Fu G, Liu W, Feng S, Yue X: Prussian blue nanoparticles operate as a new generation of photothermal ablation agents for cancer therapy. Chem Commun 2012, 48: 11567–11569. 10.1039/c2cc36456eView ArticleGoogle Scholar
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