M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin 1,2 and John Ballato 2 1. Institute of Applied Physics, Academy of Sciences, Kishinev, Moldova, 2. Clemson University, SC, USA

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA In the present paper we discuss preparation and properties of the GaP nanoparticles and light emissive films on the base of some GaP/polymer nanocomposites. This work has been fulfilled in framework of the joint USA/Moldova, Italy, Romania STCU ( ) 4610 Project “Advanced Light Emissive Device Structures”, , sponsored by the US DOS, and continue our efforts, discussed at the 2006, 2010 and 2011 Nanotech Conferences, TMS Annual Meetings, Conferences and Symposia, and published in the relevant proceedings and papers with the focus being to advance the quality and light emissive properties of GaP nanocomposites and using our new results in preparation of closed to ideal bulk GaP single crystals, different methods of GaP nanoparticles syntheses and the most optically and mechanically compatible polymers. The next stages of the Project are described in 5 Technical reports T01 – T05, the main results have been published in papers and presented at the TMS, NanoTech and other international conferences. The details can be presented on a request of possible future partners. Stage 1. Development of technology for growth of pure and doped GaP nanocrystals. Stage 2. Comparison of the properties of nanocrystals and bulk single crystals. The main results are described in the chapter 19 ”Long-Term Convergence of Bulk- and Nano-Crystal Properties”, InTech open access book “Optoelectronics – Materials and Technics”, (2011). This activity will be prolonged in the next joint projects and in edited by us new InTech open access book “Optoelectronics”, call for contribution in this edition is presented on the Information Desk of this conference. Motivation 2

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Stage 3. Development of methods of incorporation of the GaP nanoparticles into polymers. PGMA, PGMA-co-POEGMA, BPVE and THF polymers were used for preparation of GaP nanocomposites suitable for light emissive luminescent device structures. These nanocomposites provide significant enhancement of blue-shifted Luminescence from which novel light emissive device structures may be fashioned. The nanocomposites on the base of the noted above polymers were used for preparation and test of film light emissive device structures (display models) described in the technical report T04. Stage 4. Fabrication and characterization of nanocomposite polymer optical fiber snd film device structures. We show that the composites of GaP nanoparticles dispersed in dielectric polymers can be a good base for light emissive luminescent device structures. In particular, the resulting nanocomposites show discussed here interesting phenomena leading to dramatic 1 eV expansion of GaP luminescence to the UV spectral region. The film device structures demonstrate broadband luminescence in the region from UV until yellow-red with controlled width and position of maximum with the luminous intensity up to 1 cd compared with industrial light emitting diodes. Characterization by the RLS, XRD, TEM and AFM methods helped to improve technology for preparation of nanocomposites. Stage 5. Comparison of the obtained and anticipated results. Generalization and dissemination of the results. 3

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Figure 1. RLS from GaP nanoparticles of different treatment prepared from white or red P (spectra 2-4) in comparison with perfect GaP bulk single crystals (spectrum 1). Please see the details in the text. 4

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Figure 2. X-ray diffraction from GaP nanoparticles (2-4) in comparison with the diffraction from perfect GaP single crystal (spectrum 4). 1. White P, the best low temperature synthesis, well-treated powder. 2. White P, not the best performance and powder treatment. 3. Red phosphorus, the best result. 5

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Figure 3. Luminescence of perfect bulk GaP single crystals (1) in comparison with the luminescence of GaP nanoparticles and GaP/polymers nanocomposites (2-3). Nanoparticles have been prepared using white P by mild aqueous or colloidal synthesis at decreased temperature and stored as the dry powder (spectrum 2)or suspension in a liquid (spectrum 3). 6

Figure 4. Band structure of GaP 7

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA First attempts to prepare GaP nanoparticles yielded room temperature luminescence with maximum shifted only to 2.4 eV in comparison with the new maximum at 3.2 eV. It confirms significant achievements in technology of GaP nanoparticles and GaP/polymers nanocomposites. On the base of these improved technologies for preparation of GaP nanoparticles and GaP/polymer nanocomposites we can change within the broad limits the main parameters of luminescence and expect to create a framework for novel light emissive device structures using dramatic 1 eV expansion of GaP luminescence to UV region. Conclusions 8

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Acknowledgements The authors are very grateful to the US Dept. of State, Institute of International Exchange, Washington, DC, the US Air Force Office of Scientific Research, Science & Technology Center in Ukraine (STCU), Clemson University, SC, Istituto di elettronica dello stato solido, CNR, Rome, Italy, Universita degli studi, Cagliari, Italy, Joffe Physico-Technical Institute, St. Petersburg State Technical University, Russia and Academy of Sciences of Moldova for support and attention to our extended ( ) research efforts. 9

M a r c h , – O r l a n d o, F l o r i d a Dramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer NanocompositesDramatic Expansion of Luminescence Region in GaP/Polymer Nanocomposites Sergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USASergei Pyshkin1,2 and John Ballato21. Institute of Applied Physics, Academy of Sciences,Kishinev, Moldova, Clemson University, SC, USA Thank you for your kind attention ! 10