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Pure and Mn+2-doped Zn2SiO4 nanocomposite materials were synthesized using a sol–gel method. The structural, optical, dielectric and magnetic properties of prepared samples were studied using different techniques. X-ray diffraction results show that the dominant phase is willemite (α-Zn2SiO4) with rhombohedral structure and average crystallite size varied from 70 to 90 nm. Photoluminescence spectra, PL of Zn2SiO4, have two broadband emissions centered at 375 nm and 760 nm. PL spectra of Zn2SiO4/Mn is characterized by one dominant peak at 525 and attributed to 4T1–6A1 transitions of Mn2+ ions. Photoluminescence excitation, PLE of Zn2SiO4/Mn at 78 K, has strong excitation band from 240 to 300 nm with maximum at about 255 nm (4.9 eV) compared to the bands in UV–Vis range. Dielectric constant, dielectric loss tangent and electrical conductivity of prepared samples are studied as a function of electric field frequency and indicated a strong dependent on Mn+2 ions. Zn2SiO4 and Zn2SiO4/Mn+2 have diamagnetic properties at room temperature at 300 K, while Zn2SiO4/Mn+2 has a ferromagnetic behavior at 5 K. [ABSTRACT FROM AUTHOR]

Yellow and green lights emitting vanadium doped Zn 2 SiO 4 particles embedded in a SiO 2 host matrix were synthesised by a sol–gel method. After the incorporation of ZnO:V nanoparticles in a silica monolith using a sol–gel method with supercritical drying of ethyl alcohol in two steps, it is heat treated in air at 1200 °C and 1500 °C for 2 h in order to obtain the α and β phases of Zn 2 SiO 4 nanocomposites. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the phase purity, particle size and morphology. In addition, photoluminescence (PL) is used for optical studies. The PL shows a band centred at about 540 nm in the case of α-Zn 2 SiO 4 . In the case of β-Zn 2 SiO 4 , the PL reveals a band centred at about 526 nm. It is suggested that radiative defects attributed to the vanadium in the interfaces between the Zn 2 SiO 4 particles and the SiO 2 host matrix resulting from heat treatment, were responsible for theses luminescence bands. [ABSTRACT FROM AUTHOR]

We report a novel synthesis process of V doped β-Zn2SiO4 green nanophosphors based on sol–gel method. After the incorporation of ZnO:V nanoparticles in a silica monolith using a sol–gel method with supercritical drying of ethyl alcohol in two steps, it is heated in air at 1500 °C for 2 h. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize the phase purity, particle size and morphology. In addition, photoluminescence (PL) is used for optical studies. XRD results indicate that pure phase of β-Zn 2 SiO 4 with triclinic structure was obtained after thermal treatment at 1500 °C. The PL shows an new intensive luminescence band in the visible range centered at about 526 nm, attributed to vanadium in the interfaces between the Zn 2 SiO 4 nanoparticles and the SiO 2 host matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] The synthesis of Zn2SiO4 nanocomposites. [•] Structural and optical characterizations of Zn2SiO4, Zn2SiO4:Mn and Zn2SiO4:V nanocomposites. [•] The willemite α-Zn2SiO4 structure was formed to the heat treatment temperature 1200°C. [•] The powder exhibits a nanometric size. [•] Strong bands of luminescence have appeared. [ABSTRACT FROM AUTHOR]

Abstract: Zn2SiO4 and Zn2SiO4:Mn particles embedded in SiO2 host matrix prepared by sol gel method under supercritical conditions of ethyl alcohol in two steps. Were prepared by a simple solid-phase reaction under natural atmosphere at 1200°C after the incorporation of ZnO and ZnO:Mn nanoparticles, respectively, in silica monolith. In the case of SiO2/Zn2SiO4 nanocomposite, the powder with an average particle size of 80nm shows a strong luminescence band centred at around 760nm in the visible range. In addition, the PL spectrum for the SiO2/Zn2SiO4:Mn nanocomposite showed that a dominant peak at 525nm appeared, which originated from the 4T1–6A1 transitions of Mn2+ ions. The luminescence properties of nanocomposites were characterized by emission and excitation spectra as well their dependencies of upon temperature and power excitation density. [Copyright &y& Elsevier]

Highlights: [•] Elaboration of (V, Al) co-doped ZnO nanoparticles. [•] Structural and optical characterizations of these nanoparticles. [•] The powder shows an average particle size of 25nm. [•] A strong luminescence band in the visible range is appeared. [Copyright &y& Elsevier]

Abstract: Green light emitting Mn2+ doped Zn2SiO4 particles embedded in SiO2 host matrix were synthesized by a sol–gel method. After the incorporation of ZnO:Mn nanoparticles in a silica monolith using sol–gel method with supercritical drying of ethyl alcohol in two steps, it was heat treated in air at 1200°C for 2h in order to obtain the SiO2/α-Zn2SiO4:Mn nanocomposites. The microstructure of phosphor crystals was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). XRD results indicate that the pure phase α-Zn2SiO4 with rhombohedral structure was obtained after thermal treatment at 1200°C. The SiO2/α-Zn2SiO4:Mn nanocomposites with a Mn doping concentration of 1.5at% exhibit two broadband emissions in the visible range: a strong green emission at around 525nm and a second one in the range between 560 and 608nm. This nanocomposite with a Mn doping concentration of 0.05 shows the highest relative emission intensity. Upon 255nm excitation, the luminescence decay time of the green emission of Zn2SiO4:Mn around 525nm is 11ms. The luminescence spectra at 525nm (4T1–6A1) and lifetime of the excited state of Mn2+ ions-doped Zn2SiO4 nanocrystals are investigated. [Copyright &y& Elsevier]

Abstract: The sol gel method is used for the preparation of undoped and manganese-doped Zn2SiO4 particles embedded in SiO2 host matrix with supercritical drying of ethyl alcohol in two steps. Zn2SiO4 and Zn2SiO4: Mn were prepared by simple solid-phase reaction in a natural atmosphere at 1200°C after the incorporation of the nanoparticles of ZnO and ZnO: Mn, respectively, in the silica monolith. The photoluminescence (PL) measurements show a band centered at about 760nm in the case of non-doped Zn2SiO4 which is attributed to energy transfer from Zn2SiO4 particles to NBOHs interface defects. In the case of Manganese doped Zn2SiO4, the PL reveals a band centered at about 525nm attributed to Mn2+ in Zn2SiO4. Photoluminescence excitation (PLE) measurements show different origins of the emission. It was suggested that electronic transition 4T1(4G)→6A1(6S) associated with Mn2+ ions in willemite and the presence of Mn2+ in intensive crystal field were responsible for these luminescence band centered at 525nm. [Copyright &y& Elsevier]

Abstract: Undoped and vanadium-doped Zn2SiO4 particles embedded in silica host matrix were prepared by a simple solid-phase reaction after the incorporation of ZnO and ZnO:V nanoparticles, respectively, in silica monolith using the sol–gel method with supercritical drying of ethyl alcohol in two steps. After supercritical drying and annealing in the temperature range between 1423 and 1473K in an air atmosphere, the photoluminescence (PL) measurements show a band centered at about 760nm in the case of non-doped Zn2SiO4 which is attributed to energy transfer from Zn2SiO4 particles to NBOHs interface defects. In the case of vanadium doped Zn2SiO4, the PL reveals a band centered at about 540nm attributed to the vanadium in the interfaces between Zn2SiO4 particles and SiO2 host matrix. Photoluminescence excitation (PLE) measurements show different origins of the emission bands. The PLE band (∼240–350nm) may be understood as an energy transfer process from O2− to V5+ which occurs intrinsically in the vanadyl group. [Copyright &y& Elsevier]

Abstract: We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol–gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10at.% has been investigated. After treatment in air at different temperatures, the obtained nanopowder was characterised by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). Analysis by scanning electron microscopy at high resolution shows that the grain size increases with increasing temperature. Thus, in the case of thermal treatment at 500°C in air, the powder with an average particle size of 25nm shows a strong luminescence band in the visible range. The intensity and energy position of the obtained PL band depends on the temperature measurement increase. The mechanism of this emission band is discussed. [Copyright &y& Elsevier]

Abstract: Manganese-doped Zn2SiO4 particles imbedded in silica host matrix were successfully prepared by a simple solid-phase reaction under natural atmosphere at 1200°C for 2h after the incorporation of ZnO:Mn nanoparticles in silica aerogel monolith using sol–gel method with supercritical drying of ethyl alcohol in two steps. The obtained sample, exhibits a strong photoluminescence (PL) bands in the visible range at 525 and 610nm. Photoluminescence excitation (PLE) measurements show different origins of the emission. It was suggested that electronic transition associated with Mn2+ ions in willemite and the presence of Mn2+ in intensive crystal field were responsible for theses luminescence bands. In the other hand, this emission of the final composite is time stable: no change in the spectra was observed even after being aged for over 1 year. [Copyright &y& Elsevier]

Abstract: We report the elaboration of vanadium-doped ZnO nanoparticles prepared by a sol–gel processing technique. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. Vanadium doping concentration of 10at% has been investigated. The obtained nanopowder was characterised by various techniques such as particle size analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). In the as-prepared state, the powder with an average particle size of 25nm presents a strong luminescence band in the visible range after thermal treatment at 500°C in air. The energy position of the obtained PL band depends on the wavelength excitation and presents a blue shift with measurement temperature increase. Different possible attributions of this emission band will be discussed. [Copyright &y& Elsevier]

Silica host matrix reached by manganese-doped zinc silicate nanoparticles (SiO 2 /Zn 2 SiO 4 :Mn) were in-situ synthesized by a sol–gel process. In our approach, we synthesis ZnO:Mn nanoparticles in supercritical conditions of ethanol. After the incorporation of these nanoparticles in silica host matrix, a heat treatment at 1200 °C and 1500 °C for 2 h was performed for the elaboration of SiO 2 /Zn 2 SiO 4 :Mn nanocomposites. Then, these samples were characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence (PL). These samples exhibit broad green and yellow PL bands depending on synthesis temperature. The SiO 2 /Zn 2 SiO 4 :Mn prepared at 1200 °C exhibit a green emission centered at about 525 nm while the yellow emission centered at 575 nm resulted from SiO 2 /Zn 2 SiO 4 :Mn prepared at 1500 °C. These two emissions are originated from internal transition in Mn 2+ ion doped zinc silicate nanoparticles and the emission wavelength is correlated to the local crystalline field which is fixed by the crystallographic phase. [ABSTRACT FROM AUTHOR]