Barium Titanate Glass Research Articles

Field-assisted sintering of barium titanate and 45S5 bioactive glass for biomedical applications

The development of electrically active biomaterials, which create electrical cues on demand to foster cellular stimulation, remains a challenge. Here, we utilized a Field-assisted sintering approach to densify barium titanate and 45S5 bioactive glass to create a piezoelectric and potentially bioactive composite. By using Field-assisted sintering, we aimed to fabricate dense piezoelectric specimens, preserving a low degree of crystallization of the bioactive glass to keep bioactivity as high as possible. Therefore, we have varied the compositions of the materials and processed them at different sintering temperatures. This enabled us to produce dense test specimens in the 94 %–98 % relative density range. The samples were successfully polarized, and piezoelectric charge constants d33 were determined for the composites. The content of bioactive glass and the sintering temperature influence the charge constant d33. It is in the range of 0.8–3.4 pC/N for the composites, approximately in the order of magnitude assigned to natural tissues such as bone. X-ray diffraction was used to analyze the composition of the processed samples and to investigate the influence of an additional thermal post-treatment. Altogether, we established a process window for field-assisted sintering, allowing the fabrication of a piezoelectric and potentially bioactive biomaterial for tissue engineering.

Initial results from SEM-EDX and LA-ICP-MS chemical characterisation of barium titanate glass microspheres

Barium titanate glass microspheres are used in a variety of applications, particularly for retroreflective materials, owing to their high refractive index. These microspheres can be released into the environment or found at crime scenes due to damage or decomposition. Chemical characterisation of barium titanate glass microspheres using SEM-EDX and LA-ICP-MS showed a good discrimination of the studied materials from each other. The ubiquitously used material has the potential to characterise microtraces at crime scenes or sources of anthropogenically induced particle release in environmental studies, making it a valuable feature.

Probe-Type Fiber Optic Biosensor Based on Barium Titanate Glass Microsphere Enhanced SPR Effect for Virus RNA Detection

Probe-Type Fiber Optic Biosensor Based on Barium Titanate Glass Microsphere Enhanced SPR Effect for Virus RNA Detection

Super-resolution imaging based on cascaded microsphere compound lenses.

In this paper, a cascaded microsphere compound lens (CMCL) is introduced, in which a 20-µm-diameter barium titanate glass (BTG) primary microsphere and a 250-nm-diameter or 200-nm-diameter polystyrene (PS) secondary microsphere array constitute CMCL1 and CMCL2, respectively. The field of view (FOV) depends on the size of the BTG microsphere, while the waist of the photon nanojet (PNJ) can be adjusted by the size of the PS microsphere. The narrower the waist of the PNJ, the higher the imaging resolution. In the experiment, a 200-nm-diameter hexagonally close-packed PS nanoparticle array is successfully observed by the CMCL with a high magnification of ∼11.6× and a FOV of ∼14µm, while the single BTG microsphere is incapable of observing the array. The point spread function is used to quantify the resolution of the CMCL. A well-designed CMCL can improve the imaging performances of a microsphere-assisted microscope.

Whispering Gallery Mode Microresonator Sensor Integrated in Exposed Core Fiber for Label-Free DNA Hybridization Detection

A novel optical fiber sensor using exposed-core fiber (ECF) to excite whispering gallery modes (WGMs) within a high refractive index barium titanate glass microsphere is proposed for achieving label-free real-time specific DNA detection. The microsphere is encapsulated into the exposed channel of the ECF allowing for physical stability while excited WGMs via the evanescent field. The structure enables the sensing area to be exposed to a large amount of aqueous solution and better contact with the sample to be analyzed. Using a transmission measurement, a high Q-factor in the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> is obtained in an aqueous environment. To the best of our knowledge, this is the best Q-factor level obtained by the in fiber WGM sensor in an aqueous environment. Specific sequences of probe DNA are then bound to the surface of the microsphere so that specific detection of complementary DNA can be realized by tracking the wavelength shift the WGM resonance. Experimental results show a red shift of 5.6 pm for complementary DNA hybridization detection and less than 1 pm fluctuation for non-complementary DNA detection. The portable integrated sensor with miniature size has great potential for aqueous environmental sensing applications in the fields of diseases diagnostics, chemical analysis, and environmental protection.

Microsphere Coupled Off-Core Fiber Sensor for Ultrasound Sensing.

A compact fiber ultrasound-sensing device comprising a commercially available Barium Titanate (BaTiO3) glass microsphere coupled to an open cavity off-core Fabry–Perot interferometer (FPI) fiber sensor is proposed and demonstrated. The open cavity is fabricated through splicing two segments of a single mode fiber (SMF-28) at lateral offsets. The lateral offset is matched to the radius of the microsphere to maximize their coupling and allow for an increased sensing response. Furthermore, the microsphere can be moved along the open-air cavity to allow for tuning of the reflection spectrum. The multiple passes of the FPI enabled by the high refractive index microsphere results in a 40 dB enhancement of finesse and achieves broadband ultrasound sensing from 0.1–45.6 MHz driven via a piezoelectric transducer (PZT) centered at 3.7 MHz. The goal is to achieve frequency detection in the MHz range using a repeatable, cost effective, and easy to fabricate FPI sensor design.

Temperature dependent electrical transport behavior of (100-x)Bi2O3-x(BaTiO3) glass system

Impedance measurements were performed as a function of temperature (RT to 700 K) in the frequency range (1 Hz-1MHz) on fabricated Bismuth Barium Titanate glass samples. Dielectric permittivity is found to be increased on increasing both the temperature and BaTiO3 (BT) content in highly polarizable glass matrix of Bi2O3. Experimental data obtained for imaginary part of electric modulus (M″)has been fitted theoretically using non-exponential Kohlrausch-Williams-Watts (KWW) function, however Jonscher's universal power law has been employed to analyze the frequency dependent ac conductivity. The calculated activation energy values for both the samples have been found to be in close agreement with each other and qualify for doubly ionized oxygen vacancies, proposing that the similar kind of charge carriers are involved in the relaxation and conduction mechanisms. Stretched exponent (β) of Modulus and power exponent (n) of ac conductivity, estimated from theoretical fitting of experimental data, have been found to be dependent on temperature and BT (BaTiO3) content. On increasing temperature, an increase in values of (n) suggests that non-overlapping small polaron tunneling (NSPT) model can be easily applied to explain ac conduction and hopping transport mechanisms of the fabricated glass samples.

Optoplasmonic-Enhanced Imaging of Monolayer Polystyrene Nanoparticle Arrays by Barium Titanate Glass Microsphere-Assisted Microscopy: Implications for Nanoparticle Characterization

Low-contrast nanoparticles are difficult to detect optically because they weakly interact with photons. In this work, we have addressed this challenge by developing optoplasmonic hybrid structures composed of barium titanate glass (BTG) microspheres and Blu-ray disk (BD) substrates deposited with multilayer metal/dielectric coatings. A 300 nm and a 250 nm hexagonally close-packed polystyrene (PS) nanoparticle monolayer sample self-assembled on both a BD substrate and a metal one (glass slide deposited with the same multilayer coatings) can be discerned by BTG microsphere-assisted microscopy, and the contrast of the virtual images of the sample on the BD substrate is enhanced compared to that of the metal substrate. When the size of BTG microspheres is 20–30 μm, the contrast of the observed virtual images is the best. Moreover, the Talbot images of 300 nm PS nanoparticle arrays assembled on the BD substrate can also be experimentally observed. We can also distinguish 200 nm PS nanoparticles assembled into a one-dimensional stripe structure on the BD substrate. Numerical simulations reveal that the electric field among the gaps of PS nanoparticles and the contacting areas between the nanoparticles and a metal/BD substrate is enhanced, and the enhanced electric field of the sample placed on the BD substrate is stronger than that of the sample placed on the metal substrate. In addition, the enhanced electric field is the strongest when the BTG microsphere size is 20–30 μm in optoplamonic structures. The simulated results fit well with the experimental ones, indicating that the enhanced electric field improves the resolution of microsphere-assisted microscopy in imaging low-contrast PS nanoparticle samples.

Ballistic delivery of compounds to inner layers of the cornea is limited by tough mechanical properties of stromal tissue

The barrier characteristics of the cornea are interrogated using the impact of micro-particles into ex vivo porcine cornea. Using a commercial gene gun (BioRad; PDS1000), microparticles were accelerated and made to embed in target materials: either ballistic gelatin as a reference or corneal tissue. Statistical analysis of penetration of polydisperse spherical microparticles (5–22 μm dia.) with density of 2.5 g/cc, 4.2 g/cc, and 7.8 g/cc (soda-lime glass, barium-titanate glass and stainless steel; more limited examination of 1.1 g/cc polyethylene and 19.2 g/cc tungsten) spanned almost two decades in kinetic energy. Penetration profiles in ballistic gelatin show that the particle embedding depth is sensitive to particle size and density. In the cornea, penetration is a weak function of size and density, and the corneal stroma is an effective stopping medium for high velocity microparticles. Despite the high water content of corneal tissue (76% w/w) compared to the stratum corneum of skin (40% w/w), the resistance to penetration of the cornea is comparable to what is seen in previous research of penetration in skin tissue. Using low density polymer particles with a therapeutic agent payload, it is demonstrated that bulk material can be ballistically delivered to the central 1 cm2 of the corneal epithelium in an even layer with high bioavailability of therapeutic compound.

Multicolor emission and energy transfer dynamics in thermally stable Dy3+/Eu3+ co-doped ZPBT glasses for epoxy free w-LEDs application

Dy3+ doped and Dy3+/Eu3+ co-doped zinc phosphate barium titanate (ZPBT) glasses were successfully synthesized by melt quenching procedure. The co-doped glasses revealed emission peaks in the blue, yellow, orange, and red spectral regions. The combinations of these emission yield white light (cool, neutral, and warm) and orangish-red light. The tunable emission is attained by appropriately regulating Eu3+ concentrations and excitation wavelengths. The emission and decay analysis revealed the energy transfer arising due to dipolar-dipolar interaction from Dy3+ to Eu3+. The emission intensity and the chromaticity shift observed at 423 K were 72.54 % and 7.74 ×10−3, respectively signifying the strong thermal stability of the co-doped ZPBT glass. An epoxy-resin free device was demonstrated using 1.0 mol% Dy3+/Eu3+ co-doped glass and 385 nm n-UV LED chip. The results mentioned-above indicate that Dy3+/Eu3+ co-doped synthesized glasses are promising candidates for epoxy-free high powered w-LED applications under n-UV excitation.

Coated High-Refractive-Index Barium Titanate Glass Microspheres for Optically Trapped Microsphere Super-Resolution Microscopy: A Simulation Study

As water is normally used as the immersion medium in optically trapped microsphere microscopy, the high-refractive-index barium titanate glass (BTG) microsphere shows a better imaging performance than the low-index polystyrene (PS) or melamine formaldehyde (MF) microsphere, but it is difficult to be trapped by single-beam optical trapping due to its overly high refractive index. In this study, coated BTG microspheres with a PS coating have been computationally explored for the combination of optical trapping with microsphere-assisted microscopy. The PS coating thickness affects both the optical trapping efficiency and photonic nanojet (PNJ) property of the coated BTG sphere. Compared to the uncoated BTG sphere, the coated BTG sphere with a proper PS coating thickness has a highly improved trapping efficiency which enables single-beam optical trapping, and a better PNJ with a higher optical intensity Imax and a narrower full width at half maximum (FWHM) corresponding to better imaging performance. These coated BTG spheres also have an advantage in trapping efficiency and imaging performance over conventional PS and MF spheres. The coated BTG microsphere is highly desirable for optically trapped microsphere super-resolution microscopy and potentially beneficial to other research areas, such as nanoparticle detection.

Determination of Microsphere-Lens Magnification Using Micro-Robotic Scanning Superlens Nanoscopy

Microsphere-assisted nanoscopy has shown great potential in recent developments in the field of super-resolution imaging. The precise control of microspheres is leading to new discoveries that can help verify the theories behind the super-resolution imaging mechanism. However, microsphere imaging involves multiple planes that have different magnification factors, which affect the determination of the overall resolution of the image. In this study, we present a flexible probe–lens assembly scheme that uses a barium titanate glass microsphere, as well as various scanning stages that can be used to freely investigate the sample surface and perform large-area super-resolution imaging (80 μm × 60 μm). The obtained resolution using this assembly under water immersion condition is 130 nm. By investigating the relationship between the magnification factors and the corresponding focus position of the different feature patterns, a remarkable difference in the focusing characteristics between arbitrary and periodic patterns was revealed. Results demonstrate the universality of the proposed method for the quantitative selection of the best focused plane and determination of the corresponding magnification factor and resolution of a microsphere virtual image for any feature pattern. The findings provide additional insights into the interpretation of arbitrary nanostructures through 3D optical imaging.

Microspherical nanoscopy: is it a reliable technique?

We looked at the typical resolution provided by microspheres in nanoobject imaging. The resolution was studied with two kinds of materials: high-index barium titanate glass and low-index polystyrene. Spheres of different sizes were taken, and thus we also checked if there is any dependence of the resolution capabilities on their dimensions. We concluded that, although we observed an increase in resolution for some of the spheres, practical considerations and lack of consistency in imaging makes this technique too cumbersome for practical applications.

Comparison of Particle Size Distributions of Reference Particles by Using Different Measuring Methods

Particle size analysis is most fundamental analysis to powder technology. However, the validation or calibration of particle size analysis, especially the laser diffraction (LD) method, was not often carried out due to the difficulty to prepare the well-known sample. For example, the validation of LD method need spherical reference particles, of which size distribution is better to have a range over one decade of size. As this request, the Association of Powder Process Industry and Engineering, Japan distributed three kinds of standard reference particles (SRP) of spherical barium titanate glass; their size ranges are 1 – 10 µm, 3 – 30 µm and 10 – 100 µm. Those particles are also fitted to the reference particles in JIS Z 8900-1 Standard.In this paper, the particle size distribution (PSD) based on volume of SRP which was converted from the number-based PSD of SRP measured by a scanning electron microscope (SEM) was compared with PSD measured by LD instruments, which was conducted by the Technical Group of Measurement and Control in APPIE. PSD results measured by LD instruments were almost same as each other. PSD by LD method was slightly different from PSD measured by SEM. This discrepancy was discussed by using by a flow type image analysis method which could measure the size of particles in the aqueous solution. It was found that sample particles could not be dispersed completely in the aqueous solution even if using dispersing instruments such as an ultrasonic bath, and that this influence was not serious to the PSD result when using the suitable operating condition of ultrasonic bath.

Large field-of-view super-resolution image obtained by manipulating submerged microsphere

Images with super-resolution can be obtained by dielectric microspheres with appropriate refractive index. However, in practical applications, the microsphere must be moved to the desired position and can scan the large specific area. Here we present a simple method of positioning a microsphere by using a four-dimensional precision translation stage. The simulations have been performed to confirm that 16 μm ϕ barium titanate glass (BTG) microsphere submerged in alcohol can obtain high quality images and the influence of the probe and the flowing liquid on imaging can be ignored. Therefore, by driving the translation stage, the submerged microsphere can scan the sample surface along the X and Y axis at the speed of 10 μm/s and the large field-of-view image can be achieved by stitching the pictures of different positions. This work has provided a new technique in super-resolution imaging and can be widely applied in field of scientific research.

Turning a normal microscope into a super-resolution instrument using a scanning microlens array

We report dielectric microsphere array-based optical super-resolution microscopy. A dielectric microsphere that is placed on a sample is known to generate a virtual image with resolution better than the optical diffraction limit. However, a limitation of such type of super-resolution microscopy is the restricted field-of-view, essentially limited to the central area of the microsphere-generated image. We overcame this limitation by scanning a micro-fabricated array of ordered microspheres over the sample using a customized algorithm that moved step-by-step a motorized stage, meanwhile the microscope-mounted camera was taking pictures at every step. Finally, we stitched together the extracted central parts of the virtual images that showed super-resolution into a mosaic image. We demonstrated 130 nm lateral resolution (~λ/4) and 5 × 105 µm2 scanned surface area using a two by one array of barium titanate glass microspheres in oil-immersion environment. Our findings may serve as a basis for widespread applications of affordable optical super-resolution microscopy.

Effective sensitization of Eu3+ and energy transfer in Sm3+/Eu3+ co-doped ZPBT glasses for CuPc based solar cell and w-LED applications

Sm3+/Eu3+ co-doped transparent Zinc Phosphate Barium Titanate (ZPBT) glasses have been successfully prepared via melt quenching technique. The photoluminescence properties and energy transfer mechanisms of these glasses were investigated in detail. The addition of Sm3+ as sensitizer expanded the excitation spectrum of Eu3+ in the Sm3+/Eu3+co-doped ZPBT glasses. The mechanism for energy transfer from Sm3+ to Eu3+ was dipole-dipole in nature, which was confirmed by Dexter energy transfer formula and Reisfeld's theory on emission spectra and Inokuti Hirayama (I-H) model on decay curves. The Sm3+/Eu3+ co-doped ZPBT glasses reveal the capability to down-convert the n-UV and blue wavelength photons located in the weakest absorption of copper phthalocyanine (CuPc), to red-emitting photons in the optimal absorption of CuPc. The evaluated CIE chromaticity coordinates for the glasses move towards the red region with the increase in Eu3+ concentration under n-UV excitation wavelength. The above-mentioned results imply that the Sm3+/Eu3+ co-doped ZPBT glasses are the potential candidate for applications in CuPc based solar cells and w-LEDs.

Development and characterization of retro-reflective colored tiles for advanced building skins

RR materials, able to reflect the solar radiation mainly toward the incident direction, are a strategy to mitigate the Urban Heat Island (UHI) phenomenon, by reducing the heat trapped inside the urban canyon.This paper introduces new ceramic tiles for outdoor applications properly treated to get RR optic properties.Traditional colored tiles were covered with a UV resistant, transparent paint containing RR microspheres for exterior applications, through an ad-hoc continuous tape casting process, developed for this specific application. The goal is to produce RR tiles through industrial continuous process in order to ensure the penetration of such innovative building materials in the market.Three types of microspheres were tested: i) clear barium titanate glass microspheres; ii) hemispherically aluminum coated barium titanate glass microspheres; iii) hemispherically aluminum coated barium titanate glass microspheres with an additional fluoropolymer coating. The obtained tiles were investigated with a spectrophotometric analysis, a study of the spatial distribution of the reflected radiation, a colorimetric analysis to evaluate changes in tiles’ original color. Reflectance is increased by clear barium titanate glass microspheres, while is almost halved by aluminum-coated spheres. All the three types of microspheres provide strong RR behavior for incident light directions from 0° to 60° with respect to the surface normal. Nevertheless, the aluminum-coated microspheres change completely the tiles’ original color, making the application of the aluminum RR tiles very limited. Clear barium microspheres instead improve the optic properties of the original tiles, with negligible effects on the color.

Contrast enhancement of microsphere-assisted super-resolution imaging in dark-field microscopy

We report a method of boosting the imaging contrast of microsphere-assisted super-resolution visualization by utilizing dark-field illumination (DFI). We conducted experiments on both 10-µm-diameter silica (SiO2) microspheres with refractive index n ∼ 1.46 under no and partial immersion in ethyl alcohol (n ∼ 1.36) and 20-µm-diameter barium titanate glass (BTG, n ∼ 1.9) microspheres with full immersion to show the super-resolution capability. We experimentally demonstrated that the imaging contrast and uniformity were extraordinarily improved in the DFI mode. The intensity profiles in the visualization also numerically confirm the enhanced sharpness for a better imaging quality when applying DFI.

Super-Resolution Imaging of a Dielectric Microsphere Is Governed by the Waist of Its Photonic Nanojet.

Dielectric microspheres with appropriate refractive index can image objects with super-resolution, that is, with a precision well beyond the classical diffraction limit. A microsphere is also known to generate upon illumination a photonic nanojet, which is a scattered beam of light with a high-intensity main lobe and very narrow waist. Here, we report a systematic study of the imaging of water-immersed nanostructures by barium titanate glass microspheres of different size. A numerical study of the light propagation through a microsphere points out the light focusing capability of microspheres of different size and the waist of their photonic nanojet. The former correlates to the magnification factor of the virtual images obtained from linear test nanostructures, the biggest magnification being obtained with microspheres of ∼6-7 μm in size. Analyzing the light intensity distribution of microscopy images allows determining analytically the point spread function of the optical system and thereby quantifies its resolution. We find that the super-resolution imaging of a microsphere is dependent on the waist of its photonic nanojet, the best resolution being obtained with a 6 μm Ø microsphere, which generates the nanojet with the minimum waist. This comparison allows elucidating the super-resolution imaging mechanism.