Lanthanide-containing functional materials - From molecular level to bulk level

This work is a comprehensive summary of research projects the author conducted when attending the PhD program at the University of Arizona. Research topics cover the structural chemistry of lanthanide-amino-acid clusters, optical up-conversion properties of lanthanide based nanomaterials, magnetic and luminescent properties of lanthanide metal-organic frameworks (MOFs), as well as two research projects focusing on transition metal MOFs, which were derived from lanthanide metal-organic framework projects. In chapter 2, the discovery of halide anion templated lanthanide-histidine hydroxide cluster and a comprehensive study of the influence of anionic size on cluster nuclearity are discussed. Both Cl- and Br- were able to serve as template anions assisting the formation of pentadeca-nuclear lanthanide hydroxide clusters for Nd, Gd and Er. When I- was used as the template anion, pentadeca-nuclear hydroxide cluster only formed in neodymium case. In erbium case a dodeca-nuclear hydroxide cluster formed when I- was used as template ion. However I- was not effective in assisting the formation of high nuclearity gadolinium hydroxide cluster. In chapter 3, doping Er3+ ion into CuxSe nanoparticles for the purpose of making efficient optical up-conversion materials is discussed. Er3+ ion was successfully doped into CuxSe nanoparticles. However no up-conversion luminescence was detected, possibly due to the in-direct bandgap nature of CuxSe. Chapter 4 discuses attaching CuxSe nanoparticles on the surface of NaYF4:Gd, Er,Yb nanorod. The purpose is to increase up-conversion efficiency of NaYF4:Gd, Er,Yb nanorod through surface plasmon resonance enhancement property of CuxSe nanoparticle. The CuxSe nanoparticles were successfully attached onto NaYF4:Gd, Er,Yb nanorod surface through exposing the suspension containing CuxSe nanoparticles and NaYF4:Gd, Er,Yb nanorods to UV irradiation. The up-conversion efficiency of NaYF4:Gd, Er,Yb nanorods was increased after CuxSe nanoparticle attachment. Chapter 5 discussed the synthesis and characterization of functional Ln(BDC)1.5•DMF (Ln = Eu, Tb, Gd) metal-organic frameworks (MOFs). The absence of OH group containing species within this MOF rendered them ideal substrates as luminescent material because luminescence quenching caused by OH groups could be avoided. A series of MOF with luminescent color ranging from red, orange, yellow and green were obtained by adjusting the relative Eu and Tb content in the MOF lattice. The magnetocaloric effect of Gd(BDC)1.5•DMF was also studied. Chapter 6 discussed doping Co2+ ion into pyrochlore-like Zn(INA)2 (INA = isonicotinate) MOF lattice for the purpose of making magnetically active pyrochlore-like MOF structures. The highest Co2+ doping concentration of 57% was successfully achieved. However, no significant magnetic frustration was observed, possibly due to the far separation between doped Co2+ ions. Chapter 7 discussed the etching of Zn(INA)2 MOF crystal to increase microporous exposure. When Zn(INA)2 MOF crystals were immersed in Co(NO3)2•6H2O acetonitrile solution, defined effective etching, which could effectively increase microporous exposure, took place. When Zn(INA)2 MOF crystals were immersed in Co(NO3)2•6H2O N,N-dimethylformamide solution, defined ineffective etching, which could not increase microporous exposure, took place dominantly. Increasing etching temperature resulted in similar but more severe etching. However, new cobalt dominant MOF phases formed when etching was performed under elevated temperature.