1. W. Huang, C. Lu, C. Jiang, W. Wang, J. Song, Y. Ni, Z. Xu,” Controlled synthesis of NaYF4 nanoparticles and upconversion properties of NaYF4:Yb, Er (Tm)/FC transparent nanocomposite thin films”, Journal of Colloid and Interface Science, 2012. 2. E. L. H. Cates,"Development of visible-to-ultraviolet upconversion phosphors for light-activated antimicrobial technology", Georgia Institute of Technology, United States, 2013. 3. E. W. Barrera Bello," Lanthanide-based dielectric nanoparticles for upconversion luminescence ", Tarragona, 2013. 4. C. J. Caling , M.SC Lond , " The use of upconverting nanoparticle to driveorganic photoreaction " , 2007. 5. Q. Lu, Y. Hou, A. Tang, Y. Lu, L. Lv, F. Teng,” Controlled synthesis and defect dependent upconversion luminescence of 6. X. Wang, G. Shan, K. Chao, Y. Zhang, R. Liu, L. Feng, Q. Zeng, Y. Sun, Y. Liu, X. Kong," Effects of Er3+ concentration on UV/blue upconverted luminescence and a three-photon process in the cubic nanocrystalline Y2O3:Er3+" , Materials Chemistry and Physics, 99, 2006. 7. E. L. Cates, M. Cho, and J-H. Kim ,”Converting visible light into uvc: microbial inactivation by Pr3+-activated upconversion materials”, Environ. Sci. Technol, 2011. 8. A. Monguzzi, M. Frigoli, C. Larpent, R. Tubino, F. Meinardi , "Low-power-photon up-conversion in dual-dye-loaded polymer nanoparticles", Advanced Materials ,2013. 9. T. N. S-Rachford, F. N. Castellano, " Photon upconversion based on sensitized triplet–triplet annihilation", Coordination Chemistry Reviews 254 , 2560–2573 ,2010. 10. F. Wang, R. Deng, J. Wang, Q. Wang, Y. Han, H. Zhu, X. Chen, X. Liu,” Tuning upconversion through energy migration in core–shell nanoparticles”, NATURE MATERIALS ,VOL 10 , 2011. 11. T. T.Y.Yan, “Rare earth nanotechnology”, Pan Standford publishing, 2012. 12. M. Lin, Y. Zhao, S. Wang, M. Liu, Z. F. Duan, Y. M. Chen, F. Li, F. Xu, T. J. Lu,” Recent advances in synthesis and surface modification of lanthanide-doped upconversion nanoparticles for biomedical applications”, Biotechnology Advances, 30, 1551–1561, 2012. 13. E. W. Barrera, M. C. Pujol, J. J. Carvajal, X. Mateos, R. Sole, J. Massons, A. Speghini, M. Bettinelli, C. Cascales, M. Aguilo, F. Diaz," Upconversion emission in (Ln,Yb):KLu(WO4)2 nanocrystals for white light generation”, Journal of Physics ,2014. 14. B.S. Cao, J.L. Wu, Z.Q. Feng, B. Dong," Investigation of near-infrared-to-ultraviolet upconversion luminescence of Tm3+ doped NaYF4 phosphors by Yb3+ codoping", Materials Chemistry and Physics, 2013. 15. D. P.Dutta, A.Ballal," Optical properties of sonochemically synthesized rare earth ionsdoped BaTiO3 nanophosphors: Probable candidate for white light emission",Journal of Luminescence, April, 2014. 16. C.R. Kasavulu, S. S. Yi," Structural, thermal and spectroscopic properties of highly Er3+-doped novel oxyfluoride glasses for photonic application", Material Research Bulletin, March, 2014. 17. B. I. Kharisov, O. V. Kharissova , U. O. Mendez, "Microwave hydrothermal and solvothermal processing of materials and compounds", 2012. 18. R. Chen, V. D. Ta, F. Xiao, Q. Zhang, H. Sun," Multicolor hybrid upconversion nanoparticles and their improved performance as luminescence temperature sensors due to energy transfer", small 9, 7, 1052–1057,2013. 19. R. Adhikari, B. Joshi, R. Narro-Garcia, E. De la Rosa ,S. Wohn Lee," Microwave hydrothermal synthesis and infrared to visible upconversion luminescence of Er3+/Yb3+ co-doped bismuth molybdate nanopowder", Journal of Luminescence 145 ,2014. 20. M. Pokhrel, A. k.Gangadharan , D. K.Sardar ," High upconversion quantum yield at low pump threshold in Er3+/Yb3+ doped La2O2S phosphor ",Materials Letters 99 ,2013. 21. F. Wang, F. Song, G. Zhang, Y. Han, Q. Li, C. Ming, J. Tian," Upconversion and pump saturation mechanisms in Er3+/Yb3+ co-doped Y2Ti2O7 nanocrystals", Journal of Applied Physics 115, 134310 ,2014. 22. B. Xue, J. Sun,"Upconversion emission properties and tunable morphologies of Y6WO12:Yb3+/Er3+ phosphor", Infrared Physics & Technology 62 ,2014. 23. A. Monguzzi, M. Frigoli, C. Larpent, R. Tubino, F. Meinardi , "Low-power-photon up-conversion in dual-dye-loaded polymer nanoparticles", Advanced Materials ,2013. 24. I. Etchart,” Metal Oxides for Efficient Infrared to Visible Upconversion”, Doctoral thesis, Cambridge, UK, August, 2010. 25. www.luminochem.com/special-security-pigments-for-security-printing-inks 26. J. M. Meruga, W. M. Cross, P. S. May, Q. Luu, G. A. Crawford, J. J. Kellar,” Security printing of covert quick response codes using upconverting nanoparticle inks”, Nanotechnology, 23, 2012. 27. A. Pandey, V. K. Rai, R. Dey, K. Kumar,” Enriched green upconversion emission in combustion synthesized Y2O3:Ho3+/Yb3+ phosphor”, Materials Chemistry and Physics, 139, 483e488, 2013. 28. G. Kaur, Y. Dwivedi, A. Rai, S.B. Rai,” Green and NIR sensitized luminescent nanophosphor: Preparation, characterization and application”, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 95, 511–516, 2012. 29. D. K. Mohanty, V. K. Rai ," Spectroscopy and visible frequency upconversion in Er3+–Yb3+:TeO2–ZnO glass",Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 121 ,p:9–13, 2014. 30. L. Shi, C. Li, Q. Shen, Z. Qiu ," White upconversion emission in Er3+/Yb3+/Tm3+ codoped LiTaO3 polycrystals",Journal of Alloys and Compounds 591 ,2014. 31. L. Shi, C. Li, Q. Shen, Z. Qiu ," White upconversion emission in Er3+/Yb3+/Tm3+ codoped LiTaO3 polycrystals",Journal of Alloys and Compounds 591 ,2014. 32. A. Stepuk, D. Mohn, R. N. Grass, M. Zehnder,K. W. Kramer, F. Pelle , A. Ferrier , W. J. Stark , "Use of NIR light and upconversion phosphors in light-curable polymers",dental materials 28 ,p:304–311, 2012. 33. W. Xiantao, L. Yong, C. Xuerui, C. Yonghu, Y. Min, "Strong dependence of upconversion luminescence on doping concentration in holmium and ytterbium co-doped Y2O3 phosphor", Journal of rear earth, 29, 6, Jun, 2011. 34. F.A. Bomfim, J.R. Martinelli, L.R.P. Kassab, N.U. Wetter, J.J. Neto," Effect of the ytterbium concentration on the upconversion luminescence of Yb3+/Er3+ co-doped PbO–GeO2–Ga2O3 glasses", Journal of Non-Crystalline Solids 354 ,2008. 35. L. Li, H. Lin, X. Zhao, Y. Wang, X. Zhou, C. Ma, X. Wei," Effect of Yb3+ concentration on upconversion luminescence in Yb3+, Tm3+ co-doped Lu2O3 nanophosphors", Journal of Alloys and Compounds 586 ,2014. 36. R. Adhikari, B. Joshi, R. N.Garcia, E. DelaRosa, S. W.Lee,” Microwave hydrothermal synthesis and infrared to visible upconversion luminescence of Er3+/Yb3+ co-doped bismuth molybdate nanopowder”, Journal of Luminescence, 145, 866–871, 2014. 37. X. Yu, M. Li, M. Xie, L. Chen, Y. Li, Q. Wang,” Dopant-Controlled Synthesis of Water-Soluble Hexagonal NaYF4 Nanorods with Efficient Upconversion Fluorescence for Multicolor Bioimaging”, Nano Research, 3, 51–60, 2010. 38. Q. Lu, Y. Hou, A. Tang, Y. Lu, L. Lv, F. Teng,” Controlled synthesis and defect dependent upconversion luminescence of Y2O3: Yb, Er nanoparticles”, Journal of Applied Physics, 115, 074309, 2014. 39. G. S. Yi, G. M. Chow,” Synthesis of Hexagonal-Phase NaYF4:Yb,Er and NaYF4:Yb,Tm Nanocrystals with Efficient Up-Conversion Fluorescence”, Advanced Functional Materials, 16, 2324–2329, 2006. 40. Y2O3: Yb,Er nanoparticles”, Journal of Applied Physics, 115, 074309, 2014. 41. R. Chai, H. Lian, Z. Cheng, C. Zhang, Z. Hou, Z. Xu, J. Lin,” Preparation and characterization of upconversion luminescent NaYF4:Yb, Er (Tm)/PS bulk transparent nanocomposites through in situ polymerization”, Journal of Colloid and Interface Science, 345, 262–268, 2010. 42. Y. Zhai, C. Zhu, J. Ren, E. Wang, S. Dong,” Multifunctional polyoxometalates-modified upconversion nanoparticles: integration of electrochromic devices and antioxidants detection”, Royal Society of Chemistry, 49, 2400-2402, 2013. 43. J. Chen, J. X. Zhao," Upconversion nanomaterials: synthesis, mechanism, and applications in sensing", Review, Sensors, 2012. 44. F T.Hosseini, A. S.Alvani, M. Taherian, H. Sameei, S. Mousakhani,” Up-conversion photoluminescence:theory to application”, Journal of studies in color world, 2, 23-28, 2012. 45. Z. Gu, L. Yan, G. Tian, S. Li, Z. Chai, Y. Zhao, "Recent advances in design and fabrication of upconversion nanoparticles and their safe theranostic applications" , Advanced Materials ,2013. 46. H. Liu, "Advancing upconversion emissions for biomedical imaging",Doctoral Thesis, Lund University, Sweden, 2014. 47. Y. Min , J. Li , F. Liu , P. Padmanabhan , E. K. L. Yeow , B. Xing ,” Recent Advance of Biological Molecular Imaging Based on Lanthanide-Doped Upconversion-Luminescent Nanomaterials”, Review, Nanomaterials, 4, 129-154, 2014. 48. Y. Sun1, Y. Chen, L. Tian, Y. Yu1, X. Kong, J. Zhao, H. Zhang,” Controlled synthesis and morphology dependent upconversion luminescence of NaYF4:Yb, Er nanocrystals”, Nanotechnology, 18, 2007. 49. T. Jiang, W. Qin , J. Zhou," Controllable synthesis and crystal structure determined upconversion luminescence properties of Tm3+ (Er3+) ions doped YbF3 and NaYbF4 Crystals",Jornalof Alloy and Compounds ,593,79-86 , 2014. 50. S. Moslemizadeh, M. Vaez-zadeh, H. Jamnezhad," UV-blue up-conversion phenomena in Nd3+ doped CaCl2 nano-crystals", Chinese Journal of Physics, 2012. 51. X. Li, F. Zhang, D. Zhao ,” Highly efficient lanthanide upconverting nanomaterials: Progresses and challenges”, REVIEW, Nano Today, 8, 643-676, 2013. 52. M. V. DaCosta, S. Doughan, Y. Han, U. J. Krull, "Lanthanide Upconversion Nanoparticles and Applications in Bioassays and Bioimaging: A Review", University of Toronto Mississauga , Canada,2014.