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Phosphate glasses were melted with fixed Eu2O3 content and varying amounts of nanodiamond (ND) powder seeking to obtain insights into the physico-chemical aspects underpinning optical properties while tuning the light-emitting properties towards photonic applications. A synergistic quantitative study incorporating X-ray diffraction, optical transmission, photoluminescence (PL) spectroscopy, Raman scattering, and differential scanning calorimetry (DSC) was carried out. The emitted light color was characterized via its CIE coordinates. The data from various techniques were correlated and discussed in the framework of energy band theory, along with the carbon-induced Eu3+ → Eu2+ reduction concomitant with non-bridging oxygen bond modifications. The optical band gap is calculated from the transmission spectra via Tauc plots to narrow from 4.1 eV to 3.3 eV with increasing carbon concentration from ND (CND ∼ 0.14–1.4 mol%). The optical band gap values appear proportional to the integral intensities of the Raman-active bands of the glass. The Eu2+ absorption band of the 4f7 → 4f65d transition is deduced from the absorption spectra of the glass and utilized to explain the optical band gap narrowing concentration-trend with 5d levels introduced below the conduction band edge. A novel method for quantifying the PL emission spectra is suggested and correlated to the CND concentration in the melt and to the optical band gap. Further, DSC was used to corroborate the data with the Raman and optical studies. The study contributes to the fundamental understanding and design of tunable light-emitting Eu-doped phosphate glasses for photonic applications.

A novel two-step method for rapid optical plasmonic transformation (ROPT) of Ag-doped phosphate glass is proposed. The ROPT process blends the time efficiency of a laser irradiation treatment with the precise temperature control over the entire glass volume. The time needed for optical transformation is reduced to 3 min, compared to 120 min during the conventional isothermal heat treatment (HT). The proposed method employs a differential scanning calorimeter (DSC) for nanoparticle (NP) synthesis. For consistent optical density comparison of the synthesized plasmonic glasses, a plasmonic merit factor, $$\zeta$$ , is introduced. The ROPT method exhibits a plasmonic factor growth rate three orders of magnitude higher, 0.14 $$\zeta$$ s−1, compared to the assessed rate of the conventional isothermal HT, 0.27 × 10–3 $$\zeta$$ s−1. The fast growth is discussed in the framework of sub-nanometer particle coalescence at temperatures 80–100 °C above the glass transition temperature of the glass nanocomposite. The proposed solid-state NP synthesis may be applied for various noble metal NPs in different types of glass matrices.

Two variants of an inflection point (IP) method for analysis of large sets of spectra, acquired in real time during non-plasmonic to plasmonic glass transformation are proposed. One of the variants is based on the time evolution of the spectral inflection point position, IP

Copper-doped silica films have been deposited on amorphous silica (fused quartz) by magnetron co-sputtering. The resulting films were characterized for copper loading/thickness by Rutherford backscattering spectrometry, and the optical properties were evaluated by absorption and photoluminescence spectroscopies. The films were subjected to thermal treatment under a 5% H2−95% Ar-reducing atmosphere and further evaluated for surface plasmon resonance (SPR) characteristics. In addition, the occurrence of Cu nanoparticles (NPs) was evaluated by transmission electron microscopy. It is indicated that the films have effective permeability for H2, and consequently, the reduction of ionic copper takes place supporting the nucleation and growth of Cu NPs. Interestingly, along with the increase in absorption intensity of Cu NPs, the processing leads consistently to significant blue shifts in the SPR peaks. Absorption spectra were then simulated by Mie theory calculations for dielectric-embedded Cu NPs in an effort to understand the influence of particle size and medium refractive index on the SPR.

Phosphate glass doped with Sm3+ ions was prepared by melting in ambient atmosphere with multi-wall carbon nanotubes (MWCNTs) added to batch materials to evaluate their impact on material optical properties. An enhanced UV transparency occurs similar to that of a glass melted just with MWCNTs. However, the glass melted only with MWCNT shows evidence of carbon-related luminescent defects, whereas the luminescence of these becomes suppressed in the Sm3+-doped glass melted with the MWCNTs. A comparison with the photoluminescence (PL) of a Sm3+-doped reference (i.e., not melted with MWCNTs) shows that addition of MWCNTs produces an improvement in Sm3+ PL in the visible and near-IR regions. The enhanced PL is observed for resonant excitation in the UV and non-resonantly under 300 nm excitation. It is suggested that the reduced host absorption contributes to the improved PL for resonant excitation of Sm3+ in the UV, while the non-resonant pathway may be related to an energy transfer from the luminescent defects produced in the host. It is the first time to our knowledge that this type of sensitized emission is reported.

A rigorous numerical optical band gap analysis is presented regarding the enhanced ultraviolet light transmission realized for barium-phosphate glasses melted with graphite, multi-wall carbon nanotubes, and nano-diamond powder. The study entails a comparative assessment wherein optimal ultraviolet transparencies were achieved. It is proposed that based on the principle of superposition, the optical absorption spectra of carbon-doped glasses may be considered as solid solutions of the host matrix and an optimal carbon-doped matrix with characteristic P O C bonds. 31P nuclear magnetic resonance (NMR) was employed for structural analysis to evaluate the relative content of the PO4 tetrahedra with two (Q2) and one (Q1) bridging oxygens. Further, the Q2/Q1 ratio from 31P NMR data was correlated with the Urbach energy. In the carbon-doped metaphosphate system, the widening of the band gap can be attributed to a decreased matrix polarizability, structurally promoted by decreased concentration of the non-bridging oxygens in agreement with the effects associated with decreased optical basicity of the matrix.

We report the specific features of basal plane stacking faults (BSFs) in ZnO nanorods (NRs), studied by temperature dependent photoluminescence and Raman spectroscopy. At low temperature (4 K) the intense band of emission at 3.321 eV is attributed to the presence of BSFs defects and Ag as an acceptor dopant in ZnO. This specific peak red-shifts with the temperature increase, occupying the position 3.210 eV at RT. The nature of the emission is explained as exciton recombination of the electrons, confined in the homo-heterojunction QW, with the holes, localized near the Ag atoms close to SFs. Raman spectroscopy revealed that Ag:ZnO nanorods have slightly downshifted positions of the modes 330 cm −1 and 440 cm −1 by 4 cm −1 , which we explain as due to the presence of BSFs. It was also observed, that the longitudinal optical phonon mode A LO , which is common polar mode for ZnO, was not detected by Raman spectroscopy in the samples with high BSFs density. This feature can be explained as due to existence of the bound charge induced by the BSFs in the NRs.

A real-time, isothermal micro-Raman spectroscopy was developed as a single technique for monitoring the solid state kinetics of dehydration and measuring its activation energy. The technique comprises of acquisition and numerical analysis of a set of isothermal time-dependent Raman spectra. α-FeOOH transformation to Fe2O3 in N2 atmosphere was continuously monitored for up to 16 h at three temperatures. Dehydration activation energy of 1.4(1) eV was estimated. The Raman band evolution of two modes with different symmetries (B1g ~ 240 cm−1 and Ag ~ 400 cm−1) and the intensity decay of B1g mode at ~540 cm−1 are analyzed independently utilizing kinetic model-free approach. The study opens new possibilities for developing versatile solid state chemical and bio-chemical Raman sensors and advances the field of analytical micro-Raman spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd.

The present work proposes that neodymium(III) performs as catalyst enhancing the precipitation of Ag nanoparticles (NPs) in silver-doped phosphate glass. In situ optical isothermal microspectroscopy was employed for evaluating the influence of the rare-earth dopant on the kinetics of Ag NP precipitation in real time in the solid-state host. A temperature-dependent first-order exponential increase with time of the peak optical density of the surface plasmon resonance of Ag NPs was observed in relation to concomitant particle nucleation and diffusion-driven growth. An Arrhenius-type plot was used for the activation energy estimation of the plasmonic Ag particles precipitation at 2.3 eV. This value is about 56% lower than the activation energy of 5.2 eV measured previously in our group [46] for the diffusion-based Ag NP growth in the glass without Nd3+ ions. Further characterizations were performed by differential scanning calorimetry, transmission electron microscopy, solid-state 31P nuclear magnetic resonance spectroscopy, and Raman scattering, in support of the in situ optical measurements. The distinctive results were discussed in the context of glass composition and structure.

Thermal, Raman scattering, optical absorption, and photoluminescence characterizations were carried out on aluminophosphate glass containing Cu+/Cu2+ along with near-infrared (IR) emitting Er3+ ions of interest to photonic applications. Material synthesis was carried out by the melt-quench technique wherein Cu+ ions were incorporated at a high concentration by addition of 10 mol% of Cu2O together with SnO. The copper oxide doping was recognized to result in a decrease of the glass transition temperature of the matrix, however Er3+ doping displayed opposite propensity. Raman measurements under 785 nm excitation were consistent with calorimetry data indicating that copper ions modify glass structural features. The degree of copper oxidation during material preparation was assessed quantitatively through the Cu2+ absorption feature around 850 nm. The presence of substantial Cu+ concurred with the significant red shift in the near-ultraviolet glass absorption edge, and was analyzed in the context of optical band gap determinations. An evaluation of the luminescence decay kinetics of Cu+ ions in the presence of Er3+ agreed with a non-radiative energy transfer which appeared more effective for excitation of Cu+ near the glass absorption edge at 400 nm. Such excitation was confirmed to result in the sensitized near-IR emission from Er3+ ions around 1.53 μm of interest to lasers, the telecommunications, and spectral conversion in photovoltaic cells.

Eight types of rare earth (RE)-doped barium phosphate glasses have been studied by differential scanning calorimetry (DSC) in the glass transition region. Proposed is a concurrent analysis of a family of heat flow data assessing the glass transition activation energies. Furthermore, the DSC data indicate correlation of the activation energy with the ionic radius of the RE dopant, in agreement with the bond strength modifications suggested by the Raman data. Estimated activation energy values between 4.0(2) eV and 4.9(2) eV are in support of P O bond exchange theory of the glass transition. It is proposed that the measured activation energy can serve as a relative quantifier of the intermediate-range order of the glass structure.

Multi-wall carbon nanotubes are systematically explored for the first time as a means to obtain an enhanced ultraviolet (UV) transparency in melt-quenched phosphate glasses. An optical characterization is carried out by UV/Vis transmission and photoluminescence spectroscopy including time-resolved measurements. 31P nuclear magnetic resonance, Raman microspectroscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy are employed to further investigate the source of the improved UV light transmission. The data suggest that the formation of P–O–C bonds is connected to the enhanced UV transparency. A model is presented accounting for the incorporation of carbon into the phosphate network facilitated by the creation of intermediate reactive oxygen species.

Glasses of BaO:P2O5 composition were melted with fixed Eu2O3 content and varying amounts of multi-wall carbon nanotubes (MWCNTs) for a spectroscopic and calorimetric study focusing on luminescent properties of interest to light-emitting devices. The optical transmission data indicated favorable Eu3+ → Eu2+ reduction with MWCNTs up to 1.0 wt% as judged by the 4f7 → 4f65d transitions of Eu2+ ions around 320 nm. A small amount of MWCNTs at 0.3 wt% lead to an improved Eu3+ luminescence under 320 nm relative to the Eu3+-doped reference likely due to a Eu2+ → Eu3+ energy transfer. On the other hand, the most intense emission around 450 nm corresponding to 4f65d → 4f7 radiative relaxation in Eu2+ was obtained for a glass melted with 0.7 wt% MWCNTs. Concentration quenching and optical band gap reduction are suggested to cause the decreased 450 nm band emission in the glass melted with 1.0 wt% MWCNTs. The glasses presented concomitant luminescence due to remaining Eu3+ ions, and the resulting emitted light under excitation at 320 nm was characterized by CIE diagram. Further, Raman spectroscopy was employed for a structural characterization, which was ultimately correlated with the thermal properties measured by differential scanning calorimetry.

Nanodiamond (ND) powder has been explored as a means for improving the ultraviolet (UV) transparency of phosphate glasses of interest to high-performance optics. Binary barium phosphate (BaO:P2O5) glasses were prepared by melting wherein increasing amounts of ND powder were added to batch materials up to 0.1 wt%. Besides a detailed UV/Vis optical analysis, structural characterizations were performed by X-ray diffraction, Raman scattering and 31P nuclear magnetic resonance spectroscopies. The data was consistent with a structural modification suggesting P–O–C bond formation accompanying the ND-induced UV transparency. Further, the reductant character of diamond was exploited for reducing CuO in the glass matrix and ultimately produce plasmonic Cu nanocomposites upon thermal treatment.

The development of photonic materials for efficient energy conversion and high-power solid-state lasers is currently pursued given the wide range of applicable technologies and the possibility to help meet global energy demands in laser fusion power plants. In this work, Cu+ ions successfully incorporated in aluminophosphate glass are recognized as near-ultraviolet (UV) sensitizers of Nd3+ ions resulting in remarkable near-infrared (IR) 4F3/2 → 4I11/2 emission at 1.06 μm. Optical absorption, solid-state 31P nuclear magnetic resonance, Raman, and photoluminescence spectroscopies characterizations are employed and assessment methods for material optical and structural properties are proposed. The spectroscopic data indicates an efficient (>50%) nonradiative energy transfer where the Cu+ ions first absorb photons broadly around 360 nm, and subsequently transfer the energy from the Stokes-shifted emitting states to resonant Nd3+ energy levels. Then, the Nd3+ electronic excited states decay and the upper lasing state 4F3/2 is populated, leading to enhanced near-IR emission. It is suggested that the physico-chemically robust Cu+/Nd3+ codoped aluminophosphate glass is a suitable candidate as solid-state laser material with enhanced pump range in the near-UV part of the spectrum and for solar spectral conversion in photovoltaic cells.

Monovalent copper ions effectively incorporated in Nd-containing phosphate glass by a single-step melt-quench method have been established as near-ultraviolet (UV) sensitizers of Nd3+ ions, resulting in a remarkable 4F3/2 → 4I11/2 emission at 1.06 μm. The spectroscopic data indicates an efficient energy conversion process. The Cu+ ions first absorb photons broadly around 360 nm, and subsequently transfer the energy from the Stokes-shifted emitting states to resonant Nd3+ energy levels in the visible. Ultimately, the Nd3+ electronic excited states decay and the upper lasing state 4F3/2 is populated, leading to the enhanced emission at 1.06 μm. The characteristic features of the Cu+ visible emission spectra and the reduced lifetime of the corresponding Cu+ donor states indicate an efficient non-radiative transfer. The Cu+/Nd3+ co-doped phosphate glass appears suitable as solid-state laser material with enhanced pump range in the near-UV part of the spectrum and for solar spectral conversion in photovoltaic cells.

An optical spectroscopy study of Pr2O3, CuO, and SnO tridoped barium phosphate glass prepared by the melt-quenching technique has been carried out, emphasizing near-infrared (IR) emission properties. The material is studied in its nonplasmonic state (as synthesized) and plasmonic form (heat-treated), aiming to elucidate the effects of Cu nanoparticles. The data indicate that Cu+ ions and Sn centers are stabilized in the melt-quenched glass. Broad ultraviolet excitations of both species can lead to near-IR emission of Pr3+ ions via energy transfer. The plasmonic nanocomposite is produced upon heat treatment as Sn2+ reduces Cu+ to Cu0 atoms, ultimately precipitating as Cu nanoparticles sustaining the surface plasmon resonance. Consequently, depletion of primarily Cu+ modified the ultraviolet excitation properties for the sensitized near-IR Pr3+ emission. Further, suppression of the Pr3+ emission from near-IR emitting states 1D2 and 1G4 was observed in the Cu nanocomposite in accord with a “plasmonic diluent” role of the nanoparticles.

In situ optical microspectroscopy has been applied for the real-time monitoring of the recently established “plasmonic diluent” effect. Concurrent absorption and photoluminescence measurements were performed as a function of time for an Ag–Dy co-doped glass at elevated temperatures. The isothermal kinetic analysis reveals: (i) a Dy 3+ photoluminescence quenching; and (ii) development of surface plasmon resonance of Ag nanoparticles. A method for monitoring the Ag nanoparticle growth rate based on the time-dependent Dy 3+ photoluminescence decrease is suggested. Dysprosium ions are proposed to act as luminescent probes of metal nanoparticle growth as a consequence of the rare-earth de-excitation via the “plasmonic diluent” effect.

The optical properties of Pr 2 O 3 and SnO co-doped barium–phosphate glass prepared by the melt-quenching technique have been investigated. Optical absorption and X-ray photoelectron spectroscopy (XPS) are employed in the characterization of tin species. The prevalence of divalent tin is indicated by the XPS data in accord with a conspicuous absorption band detected around 287 nm ascribed to twofold-coordinated Sn centers (isoelectronic with Sn 2+ ). Upon ultraviolet (UV) photoexcitation of the tin centers, near-infrared (IR) emission from Pr 3+ ions is realized. An excitation spectrum acquired by monitoring Pr 3+ emission from the 1 D 2 state at 1.03 μm revealed a broad band around 290 nm consistent with a Sn Pr donor–acceptor energy transfer channel. The data supports a mechanism starting with the singlet-to-singlet UV excitation of Sn centers, followed by the intersystem crossing populating their triplet states emitting in the visible. From these, energy transfer occurs to 3 P 0 , 3 P 1 , 1 I 6 , and 3 P 2 resonant states in Pr 3+ , from which the near-IR emitting states 1 D 2 and 1 G 4 are populated.

A comparative, temperature-dependent (80–500 K at 5 K intervals), micro-Raman spectroscopic study of 300 and 50 nm diameter ceramic BaTiO3 nanoparticles was carried out with the purpose of elucidating the nanoparticle size effect on the temperature dependence of the polar and non-polar phonons. A method for calibrating Raman intensities, along with an iterative spectral fitting algorithm, is proposed for concurrent Raman band position and intensity analysis, increasing the analytical abilities of single temperature point Raman spectroscopy. The 300 nm particles exhibit all three phase transitions, whereas the 50 nm particles do not show evidence of these phase transitions in the same temperature range. The Curie temperature appears to be a phonon converging point, irrespective of the phonon symmetry. An attempt was made to qualitatively relate the temperature-dependent Raman spectra to complimentary non-spectroscopic methods, such as heat capacity and X-ray diffraction studies. The study proves that the temperature-dependent behavior of the polar phonon, 265 cm−1, can be utilized as a sensitive phase transition probe. Copyright © 2014 John Wiley & Sons, Ltd.

A quantitative real-time assessment of the oxidation kinetics of Ag nanoparticles (NPs) embedded in nano-thin SiO2 films deposited on soda-lime glass has been carried out by a process-selective refinement of in situ optical microspectroscopy under ambient conditions. The temperature dependence of Ag NPs oxidation in the nanocomposite films was studied during thermal processing in air in the 673–773 K temperature range. An Arrhenius-type analysis of the exponential decay of the peak intensity of the surface plasmon resonance of the NPs allowed for estimating the activation energy of the process at 4.54 (±0.53)×104 J mol−1. Transmission electron microscopy and secondary ion mass spectrometry are further employed in an effort to discuss the real-time optical spectroscopy information in a broader context regarding the possible physico-chemical multistep interactions in the air–nanofilm–substrate system as a whole.

In situ optical microspectroscopy has been demonstrated effective in resolving diffusion-based growth from oxidation processes for Ag nanoparticles (NPs) embedded in silica nanofilms during thermal processing in air atmosphere. The choice of an elevated heating rate for achieving the desired terminal temperatures at which optical properties are monitored allows for increasing the sensitivity of the technique for the elucidation of NP growth. Silver NPs have been indicated to grow via Ag diffusion in an early stage of thermal treatment up to 10 min in the 570–600 °C temperature range. The isothermal time variation in Ag NP size was monitored by fitting the experimentally obtained surface plasmon resonance profiles with spectra calculated by Mie theory. The spectroscopic data was then analyzed in the context of crystal growth theory. The analysis of the time-dependent isotherms has allowed for estimating the activation energy for the process at 3.2 eV.

A novel in situ concurrent photoluminescence and absorption microspectroscopy technique is proposed for the real-time monitoring of the optical properties of rare-earth and noble metal co-doped dielectrics during isothermal processing. The technique has been successfully applied to an Ag and Sm co-doped phosphate glass, where both enhancement and quenching regimes of Sm3+ luminescence have been observed well separated in time, practical for an ‘optical tuning’ of the solid-state luminescent material. Further, relating simultaneously the luminescence with the time evolution in optical absorption allowed for discerning the effects of Ag non-plasmonic clusters as enhancers and nanoparticles as quenchers. Opportunities come forward for studying a variety of systems with relevance to a wide range of applications.

This work demonstrates that an enhanced plasmonic response can be attained and tuned for Ag nanocomposite glasses via a real-time in situ control of the plasmonic coupling between closely spaced Ag nanoparticles (NPs). The result is achieved by a two-step modification of Ag NP-doped glasses. First, confined “super-nucleation” domains are induced by high-fluence nanosecond laser irradiation promoting photofragmentation of Ag NPs in the matrix. Photoluminescence and Raman scattering spectroscopies are put to use in assessing the effects of laser treatment. Subsequently, a particle regrowth process leading to the development of strongly interacting NPs is activated during an in situ isothermal processing, which also allows for the tuning of the optical response of the material in real time. An important finding is that the post-laser thermal treatment results in a significant narrowing of the Ag NP size distribution as revealed by transmission electron microscopy. Further, valuable insights on the laser-indu...

Significant progress in understanding physico-chemical changes of noble metal species embedded in dielectrics can be achieved from the real-time monitoring of material optical properties during processing. In this work, in situ optical microspectroscopy is employed in a real-time assessment of the kinetics of Ag nanoparticle (NP) growth in the Ostwald ripening stage for NPs embedded in thick SiO2 films on soda glass, heat-treated in air atmosphere. The remarkable plasmonic evolution allows for following the variation in NP size in the framework of Mie extinction and crystal growth theories. An Arrhenius-type analysis yields an activation energy of 1.8 eV in association to aforementioned regime of NP growth. The data is discussed in the context of the atmosphere/film/substrate physico-chemical interactions alongside with previously reported results obtained by the proposed novel application of in situ optical microspectroscopy.

Significant progress in understanding noble metal species transformations in dielectrics can be achieved from the real-time monitoring of optical properties during material processing. In this work, in situ optical microspectroscopy is employed to study the Ostwald stage of Ag nanoparticle (NP) growth in nano-thin SiO2 films on soda glass substrates during heat treatment in air in the 550 – 600°C range. The evolution of Ag NP size is assessed in the framework of Mie extinction and crystal growth theories. An Arrhenius-type analysis of a set of time-dependent isotherms yields an activation energy of 1.9 eV for the Ostwald growth.

The oxidation kinetics of Ag nanoparticles (NPs) embedded in an aluminum oxide film deposited on quartz have been assessed via an in situ real-time monitoring of plasmonic evolution during thermal processing in air. A temperature-dependent exponential decay in the peak intensity of Ag NPs’ absorption was revealed, which was analyzed through first-order kinetics. An activation energy of 3.28 (±0.27) × 10 4 J mol −1 was estimated in good agreement with the oxidative dissolution of similar-sized Ag NPs in liquid phase reported by Ho et al. [11] . Results are discussed in the context of mechanistic parallelisms and physico-chemical interactions in the air-atmosphere/nanocomposite-film/substrate system.

This work presents the spectroscopic properties of trivalent samarium ions in a melt-quenched aluminophosphate glass containing silver and tin. Addition of 4 mol% of each Ag 2 O and SnO into the glass system with 2 mol% Sm 2 O 3 results in Sm 3+ ions luminescence under non-resonant UV excitation owing to energy transfer from single silver ions and/or twofold-coordinated Sn centers. Assessment of luminescence spectra and decay dynamics suggest the energy transfer mechanism to be essentially of the resonant radiative type. Moreover, a connection between the luminescent and structural properties of the rare-earth doped glass system was demonstrated. Raman spectroscopy characterization revealed that no significant variation in the glass matrix is induced by Sm 3+ doping at the concentration employed. A comparison was made with a structural study performed on the Eu 3+ doped system (containing 2 mol% Eu 2 O 3 along with 4 mol% of each Ag 2 O and SnO) where the radiative energy transfer mechanism was previously established. The data appears consistent regarding the lack of variation in glass structure upon the Eu 3+ and Sm 3+ doping in connection with the dominance of the radiative transfer in the matrix. Thermal treatment of the material leads to precipitation of Ag nanoparticles of a broad size range inside the dielectric as observed by transmission electron microspcopy. Assessment of 4 G 5/2 excited state decay in Sm 3+ ions shows no influence from the silver particles.

An in situ non-destructive optical microspectroscopy investigation of the growth of Ag nanoparticles (NPs) embedded in SiO2 nanofilms deposited on soda-lime glass has been conducted during thermal processing under a nitrogen atmosphere. The time variation in Ag NP size was monitored by fitting the surface plasmon resonance with spectra calculated by Mie theory. The spectroscopic data was analyzed in the context of crystal growth theory and the atmosphere/film/substrate physicochemical interactions. The Ag NPs were indicated to grow first through a diffusion-based process and subsequently via Ostwald ripening. The analysis of a set of time-dependent isotherms has allowed for estimating the activation energies for silver diffusion at 2.5 eV for the initial growth stage and 3.2 eV for the ripening.

Silver nanoparticle (NP) precipitation in a melt-quenched aluminophosphate glass matrix has been studied and compared for 8 mol% and 4 mol% concentrations of both Ag2O and SnO dopants. The assessment is carried out by monitoring the plasmonic evolution of glass-embedded Ag NPs in real time during thermal treatments by in situ optical microspectroscopy and complemented by transmission electron microscopy and X-ray diffraction characterization. The time variation in the surface plasmon resonance of Ag NPs is analyzed in the framework of Mie extinction theory in connection with nanocrystal precipitation in the supersaturated solid solutions. For the higher concentration of silver and tin, nucleation and growth processes were distinguished, which appeared to be temperature- and time-dependent. Hence, favorable conditions were induced for the precipitation of a large amount of small NPs in the system. On the other hand, the nucleation and growth stages were not well separated in time for the lower concentration of dopants, resulting in Ag NPs of a broad size range. However, such less-concentrated nanocomposite allowed for the precipitation of NPs much larger than those observed for the 8% doped glass. Varying the degree of supersaturation in the system has been established as an important means for the tuning of material optical properties for photonic (nanoplasmonic) applications.

The optical properties of a silver-doped phosphate glass have been monitored during thermal processing at several fixed temperatures by in situ optical microspectroscopy. Silver nanoparticle (NP) formation and growth processes were assessed by analysis of surface plasmon resonance spectral features. Nucleation and growth processes were distinguished, which appeared temperature and time dependent. While nucleation was favored at low temperatures, relatively high temperatures promoted NP growth by silver diffusion. Photoluminescence spectra acquired along with optical absorption data indicated a continuous reduction of Ag+–Ag0 pairs concomitant with NP precipitation, suggesting their role as nucleation centers. The work of Ag NP formation and the activation energy for silver diffusion were estimated.

We report an in situ non-destructive optical microspectroscopy method for measurement of the diffusion activation energy for silver in glass. The approach is based on a set of isothermal time-dependent characteristics of the surface plasmon resonance of Ag nanoparticles analyzed in the context of Mie extinction and crystal growth theories. The material studied in real time during thermal processing consisted of a melt-quenched phosphate-based glass system to which 4 mol% of Ag2O along with reducing agent SnO in the same amount were added. A diffusion activation energy of 5.2 eV was obtained and discussed in terms of glass composition. The mechanism of Ag nanoparticle growth was elucidated as well.

The effect of SnO co-doping on Er 3+ emission in the near-infrared telecommunication window has been studied in a barium-phosphate glass matrix, obtained by melt-quenching. Photoluminescence excitation spectra acquired by monitoring Er 3+ 4 I 13/2 → 4 I 15/2 emission at about 1.53 µm revealed a broad UV band around 300 nm, indicating a donor/acceptor energy transfer channel. The Sn co-doped glass exhibits a five-fold enhanced Er 3+ emission relative to an Er-doped reference. The absorption and photoluminescence spectra support a mechanism starting with excitation of twofold-coordinated Sn centers, followed by energy transfer to erbium ions. Pathways likely resulting in the enhanced Er 3+ emission are discussed.

Micro-Raman spectroscopy and the laser-induced transformation technique were used for systematic study of five coloured glazes on Saint John the Baptist (29 inch tondo), a majolica terracotta relief attributed to Luca Della Robbia and on permanent exhibit in The John and Mable Ringling Museum of Art. We suggest that Sj ions in a lead silicate matrix, called 'lead ultramarine', could contribute to the famous Della Robbia blue colour, in addition to the effect of Co atoms as suggested previously by Pappalardo et al. (2004). The original yellow glaze contains lead(II) antimonate. The green is a mixture of the yellow and blue pigments, the brown contains hematite, and the white glaze contains tin dioxide as an opacifier. The use of lead oxide as a main fluxing agent is confirmed by laser-induced micro-crystallization.

Thin films of silica containing silver nanoclusters have been deposited by magnetron co-sputtering followed by thermal annealing. Laser modification of the mean cluster size was performed using the fourth harmonic of a Nd:YAG laser with energies of between 35 and 125 mJ/cm2. The mean size of the clusters was estimated from the shape of the plasmon resonance band in the optical absorption spectra with the help of a computer simulation based on the Mie theory in static approximation. It was found that laser treatment with fluences above a certain threshold leads to a reduction of the mean size of the clusters and this reduction is greater for greater fluences. After a long treatment with the same fluence the effect saturates. The final mean size of the clusters after saturation depends only on the laser fluence and not on the initial mean cluster size. When lower laser fluences were used it was possible after laser annealing to return the mean cluster size to its initial value by thermal annealing. In this way by using a combination of laser treatment and thermal annealing a predetermined mean cluster size could be achieved. The mechanism of laser-induced cluster-size modification is discussed.

The stability of 2D antimony telluride (Sb2Te3) nanoplates in ambient conditions is elucidated. These materials exhibit an anisotropic oxidation mode, and CVD synthesized samples oxidize at a much faster rate than exfoliated samples investigated in previous studies. Optical measurement techniques are introduced to rapidly measure the oxidation modes and thickness of 2D materials. Auger characterization were conducted to confirm that oxygen replaces tellurium as opposed to antimony under ambient conditions. No surface morphology evolution was detected in AFM before and after exposure to air. These techniques were employed to determine the origin of the thickness dependent color change effect in Sb2Te3. It is concluded that this effect is a combination of refractive index change due to oxidation and Fresnel effects.

The kinetics of copper nanoparticle (NP) precipitation in melt-quenched barium-phosphate glass has been studied by in situ isothermal optical micro-spectroscopy. A spectroscopically based approximation technique is proposed to obtain information about the activation energies of nucleation and growth in a narrow temperature range (530–570 °C). Pre-plasmonic and plasmonic NP precipitation stages are identified separated in time. The process as a whole is discussed employing classical nucleation/growth theory and the Kolmogorov–Johnson–Mehl–Avrami phase change model. Activation energies of 3.9(7) eV and 2.6(5) eV have been estimated for the pre-plasmonic and plasmonic spectroscopically assessed stages, respectively. High resolution transmission electron microscopy, differential scanning calorimetry, and Raman spectroscopy were used as complementary techniques for studying the nanoparticulate phase and glass host structure. An empirical linear dependence of the diffusion activation energy on the glass transition temperature with broad applicability is suggested.

Coordination polymer thin film heterostructures of the Prussian blue analogue Ni(II)b[Cr(III)(CN)6](0.7)·nH2O (NiCr-PBA) and the 3D Hofmann-like spin crossover compound Fe(azpy)[Pt(CN)4]·xH2O {azpy = 4,4'-azopyridine} have been developed, and spin transition properties have been characterized via SQUID magnetometry and Raman spectroscopy. The magnetic response of the ferromagnetic NiCr-PBA layer (T(c) ≈ 70 K) can be altered by inducing the LIESST effect (light-induced excited spin state trapping) in the coupled paramagnetic Fe(II) spin crossover material. Whereas an increase in magnetization is measured for the single-phase Fe(azpy)[Pt(CN)4]·xH2O, a decrease in magnetization is observed for the heterostructure. These results indicate the LIESST effect alone cannot account for the sign and magnitude of the magnetization change in the heterostructure, but the temperature profile of the magnetization shows that significant changes in the NiCr-PBA network are correlated to the spin state of the Hofmann-like SCO network.

Galactose oxidase is a radical copper oxidase, an enzyme making use of a covalently modified tyrosine residue as a free radical redox cofactor in alcohol oxidation catalysis. We report here a combination of spectroscopic and magnetochemical studies developing insight into the interactions between the active site Cu(II) and two distinct tyrosine ligands in the biological complex. One of the tyrosine ligands (Y495) is coordinated to the Cu(II) metal center as a phenolate in the resting enzyme and serves as a general base to abstract a proton from the coordinated substrate, thus activating it for oxidation. The structure of the resting enzyme is temperature-dependent as a consequence of an internal proton equilibrium associated with this tyrosine that mimics this catalytic proton transfer step. The other tyrosine ligand (Y272) is covalently crosslinked to a cysteine residue forming a tyrosine–cysteine dimer free radical redox site that is required for hydrogen atom abstraction from the activated substrate alkoxide. The presence of the free radical in the oxidized active enzyme results in formation of an EPR-silent Cu(II) complex shown by multifield magnetic saturation experiments to be a diamagnetic singlet arising from antiferromagnetic exchange coupling between the metal and radical spins. A paramagnetic contribution observed at higher temperature may be associated with thermal population of the triplet state, thus permitting an estimate of the magnitude of the isotropic exchange coupling (J>200 cm−1, JS1·S2) in this complex. Structural correlations and the possible mechanistic significance of metal–radical coupling in the active enzyme are discussed.

Thin silicate sol-gel films with four different crack patterns were created reproducibly by controlling the film deposition parameters. The crack geometry, periodicity, and amplitude were studied experimentally as a function of the film thickness, curing time, and temperature. Direct evidence was found that the physical interplay between stress relief through film cracking and stress relief through film warping results in sawtooth, spiral, closed loop, or straight line crack trajectories.

Subhalf micron (0.2 nm) space and amplitude linear periodic structures and an array of dot images are obtained with the Nd:YAG laser irradiation on Kapton polyimide films, poly(ethylene terephthalate) films, spin-coated polyimide films and others. Different from the excimer laser irradiation, which requires a polarizer, our solid state Nd:YAG laser source provides polarized beams without a polarizer with advantage over excimer laser irradiation. AFM and SEM studies have been carried out. XPS studies of laser exposed areas indicate no significant chemical reactions took place on exposed areas.