N. S. Eremina

Synthesis and absorption and luminescence spectra of poly(methyl methacrylate):Cd(Mn,Pb)S composites

The reaction of cadmium, manganese, and lead trifluoroacetates with thioacetamide in methyl methacrylate yielded colloidal solutions of metal sulfides with different Cd(II): Mn(II): Pb(II) molar ratios. The colloidal particles were separated from solutions and examined by electron microscopy. Glassy polymer composites poly(methyl methacrylate):Cd(Mn)S and poly(methyl methacrylate):Cd(Mn,Pb)S were prepared by thermal polymerization of methyl methacrylate in the bulk. The transmittance of the composites at wavelengths larger than 480 nm is 92% at the sample thickness of 0.40 cm. The luminescence of the composites in the visible range is associated with cadmium sulfide. The corresponding absorption bands were recorded in the luminescence excitation spectra in the wavelength interval 300–450 nm. The effect of the matrix, Mn(II) and Pb(II) ions, and synthesis conditions on the absorption and luminescence properties of the composites was determined.

Cadmium sulfide photoluminescence in poly(methyl methacrylate)-matrix composites

Poly(methyl methacrylate)-matrix composites containing cadmium, lead, and zinc sulfides and also mixed (cadmium lead and cadmium zinc) sulfides were prepared by reacting metal salts with thioacetamide. The transmission of the composites in the range λ > 500 nm is 92% at absorbing layer thicknesses of ≤5 mm. The photoluminescence (PL) of the composites in the wavelength range 500–820 nm is due to the cadmium sulfide, and that in the wavelength range 300–550 nm arises from the zinc sulfide. It results from radiative recombination at levels of extrinsic structural defects in CdS and ZnS, respectively. The PL excitation spectra contain excitonic absorption bands of cadmium sulfide and zinc sulfide quantum dots. The PL of the cadmium sulfide in the composites is influenced by the presence of lead(II) and zinc(II) ions and the complexation of cations on the surface of the particles.

Synthesis and luminescence spectra of poly(methyl methacrylate)/CdS:Ln(III) composites

Cadmium sulfide was prepared by colloidal synthesis in methyl methacrylate (MMA). Europium and terbium salts were added to the colloidal solutions. Using MMA radical polymerization, we synthesized PMMA/CdS:Eu(III), PMMA/CdS:Tb(III), and PMMA/CdS:Eu(III):Tb(III) luminescent composites. Their luminescence is due to defects in the CdS crystals and the 5Dо → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions, respectively. It depends on the composition of the materials, complexation on the surface of the colloidal particles, heat treatment time during synthesis, excitation wavelength, and other factors.

Luminescence Spectra of Poly(methylmethacrylate)/ZnS:Eu(III),Tb(III) Composites

Colloidal zinc sulfide solutions have been prepared by reacting zinc trifluoroacetate and thioacetamide in methyl methacrylate as a reaction medium, and europium and terbium salts have been added to the solution. Using methyl methacrylate block polymerization, we have synthesized PMMA/ZnS, PMMA/ZnS:Eu(III), PMMA/ZnS:Tb(III), and PMMA/ZnS:Eu(III),Tb(III) composites. The luminescence of the composites is due to charge recombination at energy levels of structural defects and impurities in ZnS and also to 5D0 → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions. It depends on the composition and structure of the composites, excitation wavelength, and other factors. The mutual effects of the ZnS and the Eu3+ and Tb3+ ions show up as changes in the position and relative intensity of luminescence bands in the spectra of the composites.

Synthesis and luminescence of lead(II)-activated cadmium sulfide in poly(methyl methacrylate)

Optically transparent polymeric materials PMMA: Cd(Pb)S have been synthesized by polymerization of methyl methacrylate, which concurrently acts as a reaction medium for synthesis of metal sulfides, dispersion medium for the resulting colloidal solution forming during synthesis, and the base of compositions. Dependences of cadmium sulfide luminescence on the concentrations, concentration ratios of the initial compounds, reaction medium composition, and temperature have been established. The observed changes in the spectra are related to the introduction of lead(II) into compositions, complex formation on the surface of colloidal particles, and the effect of polar acetonitrile.

Synthesis and luminescence spectra of (Y2O3–YOF):Ln(III) composites

Sols were prepared by reacting yttrium, europium, and terbium trifluoroacetates with thioacetamide in ethyl acetate. The Eu3+ and Tb3+ concentrations in the sols were 0.10 to 10 wt % relative to yttrium, which corresponded to 0.061 (0.059) to 6.1 (5.9) at % Eu (Tb). The sols were converted into a gel-like state by slowly evaporating the solvent. After ripening, the gels were heat-treated at a temperature of 800°C. X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and IR spectroscopy results showed that the resultant composites consisted predominantly of a mixture of Y2O3 and YOF. The Eu3+ and Tb3+ ions were shown to substitute for Y3+ ions in the crystal lattices of the yttrium oxide and yttrium oxyfluoride. The formation of the (Eu0.6Y0.4)2O3, Eu2O3, and EuOF phases was demonstrated. We determined the types and parameters of the crystal lattices of the synthesized materials in relation to activator concentrations. The luminescence of the composites is due to the 5D0 → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions and depends on the host and activator compositions, the excitation wavelength, and other factors.

Active media on the basis of hybrid nanocomposites for tunable lasers

The laser properties and photostability of R6G was investigated in polymer solid-state matrix consisted from copolymers methylmethacrylate (MMA) with 2-hydroxyethylmethacrylate (HEMA) in the 1:1 ratio and in hybrid polymer consisted from the same monomers MMA+HEMA and tetraethoxysilane (TEOS) The 2-nd harmonic of a Nd-YAG laser was used for pumping of active media. It was shown that laser efficiency of R6G in both type of matrix is comparable whereas the laser lifetime of R6G in hybrid material is noticeably longer then in P(MMA+HEMA).