Silver Ion-exchanged Glass Research Articles

Influence of different process conditions on mechanical, optical and surface properties of silver ion exchanged soda-lime silicate glass

Recently, surface modified functional glasses have been the focus of attention for researchers. Among the other surface modification methods, ion-exchange process has become prominent in terms of cost effectiveness of the process, ease of production, not causing damage to the glass matrix. The aim of this work is to investigate how certain ion exchange and further heat treatment processes affect the mechanical, optical and surface properties of soda-lime silicate glass. The glass samples have been subjected to ion exchange at 320 °C in a molten mixture of AgNO3 and NaNO3 with molar ratios of 2:98, 5:95, respectively and heat treatment under reducing atmosphere (Ar/H2 with a 5% H2 volume fraction mixture). The study is conducted in two parts. The first part involves a batch of characterization on the untreated and the treated glass samples. The characterizations include optical transmittance, absorbance and reflectance measurements by UV–vis-NIR spectrophotometer, FTIR analyses to examine surface properties. Scratch resistance with an increasing load and flexural strength measurements were conducted on the glass samples to determine the mechanical features of the glasses. The second part of the study includes the determination of possible corrosion mechanisms and optical properties changes of the glass surfaces after environmental test. Before and after the environmental test, optical transmission and colour analysis of the specimens were realized by UV–vis-NIR spectrophotometer, FTIR analyses were conducted on the surface of the silver ion-exchanged glass samples in order to observe corrosion reaction by using the reflection technique in the 400–4000 cm−1 wavenumber range. As a result of the study, glass samples with controllable optical, surface and mechanical properties by process parameters, containing silver nanoparticles and resistant to atmospheric conditions are obtained.

UV–Visible spectral conversion of silver ion-exchanged aluminosilicate glasses

Silver ion-exchanged was employed to introduce silver into the surface layer of aluminosilicate glasses. Effects of salt composition and annealing conditions on the distribution, valence and clustering states of silver were investigated through emission and excitation spectra measurement. It was found that isolated Ag+ ions, clusters of Ag2+ and Ag22+, and other mixed species of Ag+ ions and Ag0 atoms were present in the ion-exchanged glasses. Upon UV excitation (250–400nm), silver ion-exchanged glasses showed three distinct bands centers at 420nm, 480nm and 530nm, exhibiting great potential for the UV light down-shifting. Using the silver ion-exchanged glass as cover, quantum efficiency of α-Si solar cell in the 280–318nm spectral range was improved.

Control of surface plasmon resonance in out-diffused silver nanoislands for surface-enhanced Raman scattering

We present the studies of self-assembled silver nanoislands on the surface of silver ion-exchanged glasses. The nanoislands were formed by out-diffusion of reduced silver atoms from the bulk of the glass to its surface. Control of silver ions distribution in the glass by thermal poling after the ion exchange allowed formation of relatively big, up to 250 nm, isolated silver nanoislands while without the poling an ensemble of silver nanoislands with average size from several to tens of nanometers with random size distribution was formed. The nanoislands were characterized using atomic force microscopy and spectral measurements. We used optical absorption spectroscopy for “random” nanoislands and dark field scattering spectroscopy for isolated ones, corresponding spectra showed peaks in the vicinity of 450 nm and 600 nm, respectively. The “random” nanoislands significantly enhanced Raman scattering from Rhodamine 6G, also the modification of Raman signal from deposited on the surface of the samples bacteriorhodopsin in purple membranes was registered.

Dynamics of laser-induced radial birefringence in silver-doped glasses.

Silver ion-exchanged glass exhibits nonlinear optical properties upon interacting with intense light beams. The thermal effect due to the nanoparticles' light-absorption induces radial stress, and consequently, a radial birefringence on the glass surface. The induced birefringence possesses a topological charge of 1 in the transverse plane of the glass, i.e., cylindrical symmetry. Therefore, when the glass is illuminated with a circularly polarized light beam, a portion of the incoming beam flips its polarization handedness, since the plate is birefringent, and gains an orbital angular momentum of ±2 in units of the Planck constant. This is referred to as optical spin-to-orbital angular momentum conversion, and can be understood by means of the Pancharatnam-Berry phase. Here, we design a pump-probe setup to study and observe the dynamics of optical angular momentum coupling in real time. We show that this effect can be permanent or reversible, depending on the power and interaction time of the pump beam. In particular, an intrinsic power-dependent birefringence hysteresis is observed on the sample after interaction with and the relaxation of the irradiated point.

Development of a transparent, non-cytotoxic, silver ion-exchanged glass with antimicrobial activity and low ion elution

We investigated the antimicrobial, cytotoxicity, skin irritation, and ion elution behaviors of glass doped with silver ions with respect to its application to electronic equipment such as phones and tablet screens. The microbes tested were Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum. AgNO3 powder was spread on both sides of aluminosilicate glass, and it was heated to 250–280°C for 10min. Under optimized heating conditions (260°C, 10min), the antimicrobial activity of ion-exchanged glass against bacteria and fungi was over 99.9% after 24 weeks. The glass failed to irritate the skin of experimental animals and was considered non-cytotoxic. The maximum amount of Ag ions that were eluted from the ion-exchanged glass into drinking water was measured at 0.037±0.003μgL−1, an amount which is several orders of magnitude below the standard limit of 0.1mgL−1 in drinking water. Ag ion-exchanged glass had characteristics suitable for use as a display screen, such as a light transmittance of 90% and a surface roughness of 0.704nm. Our findings suggest that glass doped with silver ions is more hygienic than non-doped glass is, and should be applied to display screens and glassware.

Physics and chemistry of antimicrobial behavior of ion-exchanged silver in glass.

The results of a comprehensive study involving the antimicrobial activity in a silver ion-exchanged glass are presented. The study includes the glass composition, the method of incorporating silver into the glass, the effective concentration of the silver available at the glass surface, and the effect of the ambient environment. A quantitative kinetic model that includes the above factors in predicting the antimicrobial activity is proposed. Finally, experimental data demonstrating antibacterial activity against Staphylococcus aureus with correlation to the predicted model is shown.

Plasmonic molecules via glass annealing in hydrogen.

Growth of self-assembled metal nanoislands on the surface of silver ion-exchanged glasses via their thermal processing in hydrogen followed by out-diffusion of neutral silver is studied. The combination of thermal poling of the ion-exchanged glass with structured electrode and silver out-diffusion was used for simple formation of separated groups of several metal nanoislands presenting plasmonic molecules. The kinetics of nanoisland formation and temporal evolution of their size distribution on the surface of poled and unpoled glass are modeled.PACS78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 68.35.bj (surface structure of glasses); 64.60.Qb (Nucleation); 81.16.Nd (micro- and nanolithography)

SERS-applicable silver nanoisland film grown under protective coating

We have used recently developed out-diffusion technique of growing silver nanoisland films on glass surface to grow silver nanoislands under TiO2 layer deposited on the glass. After covering the surface of silver ion-exchanged glasses with TiO2 film using atomic layer deposition technique and subsequent thermal processing of the samples in hydrogen their optical absorption spectra demonstrate the absorption peak corresponding to surface plasmon resonance in grown silver nanoislands. The spectral position of the peak is shifted relatively to the peak observed in the spectra of the nanoisland film grown on the surface of ion exchanged and annealed glass samples without dielectric cover. The applicability of the silver nanoislands grown under several nm thick protective TiO2 coating in surface-enhanced Raman scattering spectroscopy is demonstrated.

Enhanced fluorescence and optical power limiting in Ag-nanocomposite glasses

In this letter, we prepared and studied the plasmon, fluorescence and optical limiting properties of silver ion-exchanged glasses followed by an external thermal treatment for clusterization inside the glass matrix. TEM (Transmission electron microscopy) studies of the prepared samples provides information about the size of the nanoclusters, their size enhancement after TA (Thermal annealing) and supports the SPR band shape variations from the UV–Vis. absorption studies. Enhancement in fluorescence and optical-limiting (with excitation near to resonant value of the SPR) is ascribed to the amplified local field after metal nanocluster growth by thermal annealing.

Formation Mechanism of Silver Nanoparticles Stabilized in Glassy Matrices

In any given matrix control over the final particle size distribution requires a constitutive understanding of the mechanisms and kinetics of the particle evolution. In this contribution we report on the formation mechanism of silver nanoparticles embedded in a soda-lime silicate glass matrix. For the silver ion-exchanged glass it is shown that at temperatures below 410 °C only molecular clusters (diameter <1 nm) are forming which are most likely silver dimers. These clusters grow to nanoparticles (diameter >1 nm) by annealing above this threshold temperature of 410 °C. It is evidenced that the growth and thus the final silver nanoparticle size are determined by matrix-assisted reduction mechanisms. As a consequence, particle growth proceeds after the initial formation of stable clusters by addition of silver monomers which diffuse from the glass matrix. This is in contrast to the widely accepted concept of particle growth in metal-glass systems, in which it is assumed that the nanoparticle formation is predominantly governed by Ostwald ripening processes.

Influence of pulsed laser irradiation on precipitation of silver nanoparticles in glass

The effect of a high power Nd:YAG laser radiation on silver ion-exchanged glasses is investigated. Exposure time, spot size and energy have been varied in order to modify the size and the distribution of the metallic nanoaggregates which are formed under the laser irradiation. Optical absorption spectroscopy has been used to confirm the formation of the nanoaggregates by plasmon resonance apparition and the intensity and the decay of the resonance have been observed with the laser irradiation parameters. Quantitative composition of the samples, before and after irradiation, has been determined by energy dispersive X-ray analysis. Desorption of Na atoms and size reduction have been observed. TEM measurements have been carried out to verify the formation of silver nanoparticles.

Prism coupling characterization of planar optical waveguides made by silver ion exchange in glass

Laboratorio de Optica Integrada, Facultad de Ciencias, Universidad de Oviedo, Spain Received 11 October 2004, revised 6 May 2005, accepted 3 June 2005 Published online 29 July 2005 PACS 02.30.Zz, 07.05.Hd, 42.79.Gn, 78.20.Bh, 78.20.Ci, 82.39.Wj A modified dark-lines method of prism-coupling technique is utilized for the experimental determination of the effective index of propagating modes in a glass planar waveguide. We use to make the waveguides a silver-sodium ion exchange in a nitrate solution and sodalime glass as substrate (microscope slides). The measurements were accomplished by direct HeNe laser beam incidence and sensing the reflected light by a Thorlabs Dec110 optical detector linked to a Protek500 digital multimeter. A LabView virtual instru-ment was implemented for the automation of the measurement process. The effective indexes measured have been used to calculate the refractive index profile by IWKB method. A comparison with other results shows that our experimental setup is suitable for slab waveguide modes characterization.

Design and fabrication of a glass waveguide optical add–drop multiplexer by use of an amorphous-silicon overlay distributed Bragg reflector

We report the fabrication of a distributed Bragg reflector (DBR) on a silver ion-exchanged glass waveguide with a patterned overlay of sputter-deposited amorphous silicon (a-Si). Using this high-refractive-index overlay DBR technology, we demonstrate a fully functional glass-integrated optic add-drop multiplexer (OADM). The OADM consists of a Mach-Zehnder interferometer (MZI) containing overlay DBR gratings in both arms. The design, fabrication, and characterization procedures of the sputter-deposited a-Si overlay DBR and the ion-exchanged glass waveguide MZI are discussed in detail. The completed 3-cm-long OADM exhibited a 24-dB transmission dip with a 3-dB bandwidth of 0.5 nm. The 1-cm-long a-Si overlay DBR induced an additional attenuation of 1.2 dB. A simplified method for overlay DBR fabrication that utilizes a lift-off technique is also proposed and demonstrated.

Optical spectroscopy of silver ion-exchanged As-doped glass

Soda-lime-silicate glass containing arsenic oxide and undoped soda-lime-silicate glass (blank) are prepared by melting from pure sand (iron concentration lower than 0.01 wt%). The effect of arsenic on the optical properties of the glass with and without silver ion exchange at 325 °C for various times is investigated by optical absorption and photoluminescence spectroscopy. Emission/excitation spectra of silver ion exchanged glass allow differentiation of three stages in the silver incorporation into the glass network. First and second stages are only observed in the undoped glass ion exchanged for short times. Such stages are associated with the presence of isolated Ag +-ions and Ag +–Ag + pairs, respectively. The third stage appears in the undoped glass ion exchanged for times longer than 10 min and in the arsenic-doped glass even for exchange times as short as 1 min. Then, this stage is characterised by molecular mixed species formed with Ag + and Ag 0, which coexist with nanoparticles of metallic silver. The presence of those Ag 0-aggregates gives a yellow colour to the glasses, which show the well-know absorption band at about 400 nm due to surface plasmon resonance.

Refractive-index Profiles of Double-silver-exchanged Glass Systems

Abstract Experimental data on silver ion-exchanged glass waveguides are presented. The waveguides are prepared by a three-step route consisting of two Ag+−Na+ ion-exchanges alternated with a heat treatment, and exhibit peculiar refractive-index profiles. The reliability of two inverse Wentzel-Kramers-Brillouin reconstruction methods is also discussed for the systems at issue.

Single mode potassium and silver ion-exchanged glass waveguides with low losses and high index increase

An improved method for fabricating single mode, low loss optical waveguides using a two step potassium and silver ion exchange in glass is reported. The waveguides are compatible with optical fibers and butt coupling of diode lasers. Propagation losses, down to 0.4 dB/cm, are measured for a wavelength of 780 nm. In the single mode waveguide, an index increase of 1% is obtained, which allows small bending losses for curvatures with a radius down to 2 mm.

High finesse ring resonators made by silver ion exchange in glass

We report the fabrication of single tap ring resonators made by thermal silver ion-exchange in various types of glass substrates. The highest finesse achieved was 55 with an efficiency of 32 percent. We systematically measured losses arising from different sources such as intrinsic absorption in the glass and scattering from side wall roughness arising from the mask fabrication technique. All data was measured at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 0.6328 \mu</tex> m.

Radiation losses from single-mode optical Y junctions formed by silver-ion exchange in glass

Single-mode optical Y junctions have been fabricated using silver-ion exchange in glass. Radiation losses are given for several different input conditions to the branch arms when the Y junction is used as an optical power combiner. A minimum radiation loss of 3 dB has been measured when only one branch arm is excited.

Integrated optical waveguiding structures made by silver ion-exchange in glass 2: Directional coupler and bends

It has been shown [ Appl. Opt.22, 0000 ( 1983)] that good quality stripe dielectric waveguides can be made by silver ion-exchange in glass if the diffusion mask is of alumina, made by anodization of an aluminum thin film. In this paper we present results of an experimental investigation of directional couplers, waveguide bends, and guide attenuation in waveguides of this type. Directional coupler transfer lengths are found to be in good agreement with theoretical prediction; bends behave as expected according to an approximate theory, and attenuation is found to be low (2dB/cm for a guide width of 2 μm). The optimum radius for a 2-μm wide monomode guide is found to be ~500 μm.

Integrated optical waveguiding structures made by silver ion-exchange in glass 1: The propagation characteristics of stripe ion-exchanged waveguides; a theoretical and experimental investigation

An account of the formation and characterization of stripe waveguides formed by silver/sodium ion exchange is given. It is shown that the variation of effective index with guide width can be predicted with good accuracy using a computer model to both solve the exchange equation to obtain the refractive index profile and to calculate the modes of the resulting structure. It is found that while the use of an anodized aluminum mask results in low-loss waveguides, a metallic mask causes deposition of silver at the edges of the guide. The experimental methods used for aluminum anodization and for characterization of the waveguides are described in detail.