新型掺Tb3+硅酸盐发光玻璃的研制

在数字X射线成像系统中使用的X光-可见光转换屏具有相当重要的作用,其性能直接影响成像系统的性能。针对特殊用途开发了一种新型掺Tb^3 硅酸盐发光玻璃转换屏,可用于30MeV的γ光子的成像探测;在低能X光(100keV)作用下的空间分辨能力与301型发光玻璃相当,而在能量高达12MeV的X光的照射下,其空间分辨能力不低于1．5lp／mm,发光效率约为301型发光玻璃的3倍。并对其性能进行了实验研究,相应的测量结果为：SiO2的质量分数达到50％以上时才能得到玻璃性质较好的材料．并使发光性能得到提高,BaO和Cs2O的质量分数接近相等的条件下,Tb^3 离子的质量分数为10．5％时发光性能最好;适量的Gd^3 离子可以敏化Tb^3 发光,也能增加玻璃密度,而Ce^3 离子可以降低发光的余辉;其它的微量元素则主要影响玻璃的熔融温度。     

离子注入金红石单晶生成的金属Ni纳米晶的磁学性能研究

研究了能量为64keV、注量1×1017cm-2的Ni离子注入金红石TiO2单晶制备的植入金属纳米晶的微观结构和磁学性能。注入层的结构和磁学性能采用透射电子显微分析（TEM）和超导量子干涉磁强计（SQUID）进行分析。结果表明，金红石单晶中有尺寸为3～18nm的金属Ni纳米晶生成，注入区域基体明显非晶化。10K温度下金属Ni纳米晶的矫顽力约为16.8kA·m-1，比Ni块材的矫顽力大。样品的零场冷却/有场冷却（ZFC/FC）曲线表明，金属Ni纳米晶的截止温度约为85K。     

Preparation and characterization of a novel luminescent nanoparticles

In this paper, a new kind of fluorescent nanomaterial with morin modified alumina core and silica shell was prepared. Samples were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), photoluminescent (PL) spectroscopy and fluorescence microscope. TEM results indicated that this material could be synthesized in nanometer range. PL spectra suggested that this new synthesized material was photostable and it showed nearly no dye leakage. This was because the dye molecules could form stable complex with the reactive aluminum cations on the surfaces of the alumina particles. The excitation and emission maxima of this new luminescent material were located at 420 and 493 nm, respectively. This new kind of luminescent nanomaterial was prepared by morin, AlCl₃ and tetraethyl orthosilicate, which was very important for the large-scale and economic preparation luminescent nanoparticles because these precursors were inexpensive and the preparation process was convenient.     

Depth profiles of Ag nanoparticles in silicate glass

Silver nanoparticle composite glass has been synthesized by ion exchange and a subsequent thermal treatment method. Transmission electron microscopy (TEM) and ultraviolet-visible spectrometry were used to study the depth profiles of Ag nanoparticles in silicate glass. Results indicate that Ag nanoparticles are nearly spherical in shape with a single-crystalline structure. Also, the volume fraction of Ag nanoparticles is very high in the surface layer of 5 μm, and then decreases slowly across the depth of 30 μm, thereafter the volume fraction reduces quickly to zero at the depth of 100 μm. The plasmon resonance bi-absorptions in the surface layer of the annealed specimen at 600 °C can be attributed to bi-modal distributions of Ag nanoparticles in the layer. The bi-modal distributions can be explained by the Ostwald ripening theory. PACS 81.05.Pj; 81.07.-b; 68.37.Lp     

Synthesis, characterisation and functionalisation of luminescent silica nanoparticles

The synthesis of highly monodispersed, homogeneous and stable luminescent silica nanoparticles, synthesized using a process based on the Stöber method is reported here. These particles have been functionalised with the ruthenium and europium complexes: bis (2,2??-bipyridine)-(5-aminophenanthroline) Ru bis (hexafluorophosphate), abbreviated to (Ru(bpy)₂(phen-5-NH₂)(PF₆)), and tris (dibenzoylmethane)-mono (5-aminophenanthroline) europium(III), abbreviated to (Eu:TDMAP). Both dyes have a free amino group available, facilitating the covalent conjugation of the dyes inside the silica matrix. Due to the covalent bond between the dyes and the silica, no dye leaching or nanoparticle diameter modification was observed. The generic and versatile nature of the synthesis process was demonstrated via the synthesis of both europium and ruthenium-functionalised nanoparticles. Following this, the main emphasis of the study was the characterisation of the luminescence of the ruthenium-functionalised silica nanoparticles, in particular, as a function of surface carboxyl or amino group functionalisation. It was demonstrated that the luminescence of the ruthenium dye is highly affected by the ionic environment at the surface of the nanoparticle, and that these effects can be counteracted by encapsulating the ruthenium-functionalised nanoparticles in a plain 15 nm silica layer. Moreover, the ruthenium-functionalised silica nanoparticles showed high relative brightness compared to the free dye in solution and efficient functionalisation with amino or carboxyl groups. Due to their ease of fabrication and attractive characteristics, the ruthenium-functionalised silica nanoparticles described here have the potential to be highly desirable fluorescent labels, particularly, for biological applications.     

Erbium doping into silicate glasses to form luminescent optical layers for photonics applications

Here we summarise results of our research on the Er-containing thin surface layers in the silicate glasses and on the effect of the layers’ composition on their luminescence properties (emission at 1535 nm) in the wavelength region widely used in photonics. The optical layers were fabricated by Er³⁺ (melt)⇔Li⁺/Na⁺ (glass substrate) ion exchange in the specially designed Li₂O containing silicate glasses using various conditions (including annealing of the samples) to obtain a set of layers with diverse distribution of the Er³⁺ ions. Changes in the chemical composition of the prepared layers were suggested to avoid the concentration quenching effect and to improve their luminescence properties; special attention was paid to presence of hydrogen in the layers that may decrease the emission intensity. Rutherford Backscattering Spectroscopy and Elastic Recoil Detection were used to obtain detailed information on migration of erbium and hydrogen through the glass matrix, respectively. Photoluminescence spectra of the fabricated samples were measured (excitation at 980 nm) to examine the desired emission around 1535 nm.     

Highly luminescent silica-coated ZnO nanoparticles dispersed in an aqueous medium

Highly luminescent silica-coated ZnO nanoparticles dispersed in an aqueous medium were synthesized using the sol-gel process. The samples prepared at various temperatures exhibited an emission peak at around 480 nm (blue color) and a quantum efficiency of 60% at maximum by the quantum confinement effect of ZnO nanoparticles, with diameters ranging from 3.1 to 3.5 nm, under ultraviolet excitation. No degradation of the quantum efficiencies and no peak shifting in the emission spectra were observed for 7 days following the preparation, which indicated no growth of ZnO nanoparticles in the aqueous medium.     

Dynamics of the mechanoluminescence induced by elastic deformation of persistent luminescent crystals

When a composite of suitable dimension formed by mixing the microcrystalline or nanocrystalline persistent luminescent materials in epoxy resin is deformed at a fixed pressing rate, then the elastico mechanoluminescence (EML) emission takes place after a threshold pressure, in which the EML intensity increases linearly with the applied pressure. When the applied pressure is kept constant or decreased linearly, then the EML intensity decreases with time, in which depending on the prevailing condition, the EML intensity initially decreases at a fast rate and then at a slow rate or sometimes it decreases exponentially having only one decay time. When a small ball is dropped from a low height onto the film of a persistent luminescent material, then initially the EML intensity increases with time, attains a peak value and then it decreases initially at a fast rate and later on at a slow rate. In this case, both the peak EML intensity and the total EML intensity increase linearly with the height through which the ball is dropped onto the film. Considering the piezoelectrically induced detrapping model based on successive detrapping of exponentially distributed traps a theoretical approach is made to the dynamics of light emission induced by elastic deformation of persistent luminescent crystals and thin films. It is shown that the EML intensity depends on several parameters such as pressure, pressing rate or strain rate, temperature, density of filled electron traps, piezoelectric constant near defect centers, etc. Both, in the case of slow deformation and impact stress, the fast decay time is related to the time-constant for the decrease of pressing rate of the samples and the slow decay time of EML is related to the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. Both, the EML produced during the release of pressure and the EML produced during the successive applications of pressure take place due to the detrapping of retrapped electrons in the vacant electron traps near activator ions, in which retrapping is caused by the thermally released electrons from the filled shallow traps lying in the normal piezoelectric region of the crystals, which get filled during the detrapping of stable traps at the time of increase of pressure. On the basis of the proposed model, the dependence of EML intensity on different parameters, dynamics of EML and physical concepts of the threshold pressure, characteristic piezoelectric field for detrapping, coefficient of deformation detrapping, nonlinear increase of the EML intensity of some crystals at high pressure and higher EML intensity in the crystals having higher coefficient of deformation detrapping can be satisfactorily understood. A good agreement is found between the theoretical and experimental results. It is shown that the present study may be helpful in tailoring the intense persistent elastico mechanoluminescent materials having long lasting time.     

Excimer laser-assisted annealing of silicate glass with ion-synthesized silver nanoparticles

The effect of KrF excimer laser radiation on a composite layer consisting of sodium-potassium silicate glass with silver nanoparticles is studied as a function of the number of laser nanosecond pulses. The silver nanoparticles are synthesized by ion implantation. The measured optical absorption of the composite layer demonstrates that the silver nanoparticle size decreases monotonically as the number of laser pulses increases. Rutherford backscattering shows that laser annealing is accompanied by silver diffusion into the bulk of the glass and partial metal evaporation from the sample surface. The detected decrease in the silver nanoparticle size is discussed in terms of simultaneous melting of silver nanoparticles and the glass matrix due to the absorption of laser radiation.     

Silica encapsulation of luminescent silicon nanoparticles: stable and biocompatible nanohybrids

This article presents a process for surface coating and functionalization of luminescent silicon nanoparticles. The particles were coated with silica using a microemulsion process that was adapted to the fragile silicon nanoparticles. The as-produced core–shell particles have a mean diameter of 35 nm and exhibit the intrinsic photoluminescence of the silicon core. The silica layer protects the core from aqueous oxidation for several days, thus allowing the use of the nanoparticles for biological applications. The nanoparticles were further coated with amines and functionalized with polyethylene glycol chains and the toxicity of the particles has been evaluated at the different stages of the process. The core–shell nanoparticles exhibit no acute toxicity towards lung cells, which is promising for further development.     

Structural and luminescent properties of silicon nanoparticles incorporated into zirconia matrix

An impact of mechanical stresses on structural and photoluminescent properties of Si nanoparticles (NPs) incorporated into the zirconia thin films is reported. The stresses are found to be responsible for important structural modifications of the NPs. The zirconia matrix doped with the NPs exhibits bright red photoluminescence (PL) at room temperature due to efficient quantum confinement of the photogenerated carriers in the nanoscale Si particles. Spectral position of the PL picks depends on: mean dimension of the NPs, their concentration, stress induced deformation and order degree of the near-surface region. In general, zirconia matrix appears as a robust and reliable host media for Si NPs.     

Charge transport along luminescent oxide layers containing Si and SiC nanoparticles

The electrical conductivity of silicon oxides containing silicon and silicon-carbon nanoparticles has been investigated. By use of sequential Si⁺ and C⁺ ion implantations in silicon oxide followed by an annealing at 1100 °C, luminescent Si nanocrystals and SiC nanoparticles were precipitated. The characterization of the electrical transport has been carried out on two kinds of structures, allowing parallel or perpendicular transport, with respect to the substrate. The first type of samples were elaborated by means of a focus-ion-beam technique: electrical contacts to embedded nanoparticles were made by milling two nanotrenches on the sample surface until reaching the buried layer, then filling them with tungsten. The distance between the electrodes is about 100 nm. The second type of samples correspond to 40 nm thick typical MOS capacitors.The electron transport along the buried layer has shown a dramatic lowering of the electrical current, up to five orders of magnitude, when applying a sequence of voltages. It has been related to a progressive charge retention inside the nanoparticles, which, on its turn, suppresses the electrical conduction along the layer. On the other hand, the MOS capacitors show a reversible carrier charge and discharge effect that limits the current at low voltage, mostly due to the presence of C in the layers. A typical Fowler-Nordheim injection takes place at higher applied voltages, with a threshold voltage equal to 23 V.     

Li~+对Tb~(3+)掺杂硅酸盐玻璃闪烁性能的影响

利用高温熔融法制备了Li+掺杂Tb3+激活硅酸盐闪烁玻璃。通过Li+掺杂Tb3+激活硅酸盐玻璃的紫外可见透射光谱、发射光谱和发光衰减时间谱,研究了Li+的加入对Tb3+掺杂硅酸盐玻璃发光性能的影响。结果表明:适量Li+的加入可有效增强Tb3+激活硅酸盐玻璃的发光强度,且相比于不掺杂Li+的Tb3+掺杂硅酸盐玻璃而言,当掺入质量分数为2.0%的Li+时,Tb3+在玻璃中的最佳掺杂质量分数由12.8%提高至15.3%。其原因是Li+掺杂增加了玻璃体系中非桥氧的数量,从而有利于改善Tb3+在玻璃体中的均匀性,降低Tb3+间因非辐射跃迁而引起的能量损失,以及提高Tb3+的最佳掺杂质量分数。但当掺入Li+的质量分数超过2.0%时,会对Tb3+激活硅酸盐玻璃的闪烁光强产生负面影响,这是因为过多的非桥氧阻碍了X射线激发能达到Tb3+离子的能量传递。     

Theoretical analysis of the static quenching of optical excitations in luminescent nanoparticles

A compact analytical expression has been obtained for the kinetics of the donor-acceptor transfer of the energy and the quenching of optical excitations in spherical nanoparticles with luminescent impurities. A series of numerical experiments simulating the process have been performed using the Monte Carlo method for nanoparticles of various sizes and concentrations of acceptors. The analytical expression well describes the numerical simulation results.     

Spectral and luminescent properties of coumarins in nanoparticles from metal ion complexes

We have studied the absorption spectra of complexes of trivalent ions Y, La, Lu, and Sc with p-phenylbenzoyltrifluoroacetone that were introduced into a solution of 90% H₂O + 10% iso-C₃H₇OH in the absence and presence of either 1,10-phenanthroline or coumarins 6, 7, or 30. We have shown that these coumarins, as well as phenanthroline, are synergistic bidentate ligands that are incorporated into complexes up to concentrations comparable with concentrations of complexes and that stabilize them in the solution. We have studied the dependences of the fluorescence (cofluorescence) intensity (I _cofl) of the coumarins on their concentration in nanoparticles from the complexes mentioned above. We have shown that, in nanoparticles from complexes of Y(III), Ln(III), and Sc(III), I _cofl of coumarin 30 at high concentrations is higher than I _cofl of coumarins 6 and 7. In addition, up to concentrations of coumarin 30 comparable with the concentration of complexes in nanoparticles, there is no concentration quenching of its fluorescence. For coumarins 6 and 7, which are prone to association in the solution under study, the process of incorporating coumarins into complexes competes with their association, which leads to concentration quenching and changes in the shape of their cofluorescence spectra.     

Formation of argentic clusters and small Ag nanoparticles in soda-lime silicate glass

The formation of argentic clusters and very small Ag nanoparticles of 0.5 to 2 nm size in commercial soda-lime glass silver-doped by Ag/Na ion exchange in a mixed nitrate melt has been studied by electron microscopy and EXAFS. Particles formation was induced already during the ion exchange procedure, or by subsequent ion irradiation with 1.5 MeV He⁺ or 3 MeV Au⁺. The presence of nanoparticles was also macroscopically revealed by their surface plasmon resonance. The structural characterization indicates that specific configurations of silver oxide-like structures, so-called argentic clusters, are involved in the initial stage of nanoparticles formation.     

Formation of silver nanoparticles on the silicate glass surface after ion exchange

It has been experimentally shown that water vapor thermal treatment of silicate glasses with silver ions introduced by ion exchange leads to the formation of a silver nanoparticle layer with a high packing density on the glass surface. The results of studying the morphology of samples by atomic force and electron microscopy and X-ray spectral analysis of the composition of nanoparticles, as well as the optical density and luminescence spectra in different stages of the treatment, are presented. Mechanisms explaining the processes responsible for silver nanoparticle formation upon water vapor thermal treatment on the glass surface after ion exchange are proposed.     

Highly luminescent undoped and Mn-doped ZnS nanoparticles by liquid phase pulsed laser ablation

In this paper we report the synthesis of highly luminescent ZnS and Mn-doped ZnS nanoparticles with uniform particle size distribution by liquid phase pulsed laser ablation. The formation of nanosized ZnS crystallites was confirmed by high-resolution transmission electron microscopy (HRTEM) images. The optical properties of these nanoparticles were studied by room temperature photoluminescence (PL) spectra. The PL emission from the ZnS nanoparticles shows a sharp peak in the UV region (334 nm) corresponding to the band edge and a broad peak in the visible region which can be attributed to the sulphur vacancies, cation vacancies and surface states in the nanocrystals. The yellow emission from the Mn-doped ZnS nanoparticles can be attributed to the radiative transition between ⁴T₁ and ⁶A₁ levels within the 3d⁵ orbital of Mn²⁺.