Development of an Interactive Touchless Technology Based on Static-Electricity-Induced Luminescence.

Touchless technology has garnered significant interest in recent years because of its effectiveness in combating infectious diseases such as the novel coronavirus (COVID-19). The goal of this study was to develop an inexpensive and high-precision touchless technology. A base substrate was coated with a luminescent material that emitted static-electricity-induced luminescence (SEL), and it was applied at high voltage. An inexpensive web camera was used to verify the relationship between the non-contact distance to a needle and the applied-voltage-triggered luminescence. The SEL was emitted at 20-200 mm from the luminescent device upon voltage application, and the web camera detected the SEL position with an accuracy of less than 1 mm. We used this developed touchless technology to demonstrate a highly accurate real-time detection of the position of a human finger based on SEL.

Flexible Mechanoluminescent SrAl2O4:Eu Film with Tracking Performance of CFRP Fracture Phenomena.

Non-destructive testing of carbon-fiber-reinforced plastic (CFRP) laminates with bidirectional fiber bundles (twill-weave) using a mechanoluminescence (ML) technique was proposed. The dynamic strain distributions and fracture phenomena of the CFRP laminates in the tensile testing were evaluated by the fabricated ML sensor consisting of SrAl2O4:Eu (SAOE) powder and epoxy resin. The ML images for the ML sensor attached to the CFRP laminates with bidirectional fiber bundles gave a net-like ML intensity distribution similar to the original twill weave pattern. Specifically, it was found that the ML intensity on the longitudinal fiber bundle, which is the same as the tensile direction, is higher than that on the transverse fiber bundle. This indicates that the ML sensor can visualize the load share between fiber bundles in different directions of the CFRP laminate with high spatial resolution. Meanwhile, the ML sensor could also visualize the ultrafast discontinuous fracture process of the CFRP laminates and its stress distribution. The amount of SAOE powder in the ML sensor affects the tracking performance of the crack propagation. A higher SAOE amount leads to a fracture of the ML sensor itself, and a lower SAOE amount leads to poor ML characteristics.

Flexible Ceramic Film Sensors for Free-Form Devices.

Recent technological innovations, such as material printing techniques and surface functionalization, have significantly accelerated the development of new free-form sensors for next-generation flexible, wearable, and three-dimensional electronic devices. Ceramic film sensors, in particular, are in high demand for the production of reliable flexible devices. Various ceramic films can now be formed on plastic substrates through the development of low temperature fabrication processes for ceramic films, such as photocrystallization and transferring methods. Among flexible sensors, strain sensors for precise motion detection and photodetectors for biomonitoring have seen the most research development, but other fundamental sensors for temperature and humidity have also begun to grow. Recently, flexible gas and electrochemical sensors have attracted a lot of attention from a new real-time monitoring application that uses human breath and perspiration to accurately diagnose presymptomatic states. The development of a low-temperature fabrication process of ceramic film sensors and related components will complete the chemically stable and reliable free-form sensing devices by satisfying the demands that can only be addressed by flexible metal and organic components.

Effect of Manual Upper Eyelid Elevation on Intraocular Pressure Measurement by Four Different Tonometers.

SIGNIFICANCE: This study is the first to show that the manual upper eyelid elevation (manual UEE) that is commonly used to prevent disruption of the IOP measurement due to blinking or upper eyelid contact with the tip of the tonometer does not affect the IOP values. PURPOSE: We investigated whether manual UEE affects the IOP readings using three rebound tonometers (Icare TA01i, Icare PRO, and Icare ic100) and Goldmann applanation tonometry (GAT). METHODS: One eye was measured for 101 patients (56 eyes of primary open-angle glaucoma patients and 45 healthy subjects). The IOPs were measured without and with manual UEE. Each IOP was measured twice; the measurement order using the tonometers was randomly selected. In addition, palpebral fissure height (distance between the upper and lower eyelids) was measured. RESULTS: The IOPs without manual UEE were 12.1 ± 2.9, 13.3 ± 2.7, 11.7 ± 2.9, and 16.0 ± 3.2 mmHg (Icare TA01i, Icare PRO, Icare ic100, and GAT), and those with manual UEE were 12.3 ± 3.0, 13.3 ± 2.8, 11.7 ± 2.9, and 16.0 ± 3.3, respectively. No significant difference was found between the IOP without and with manual UEE (IOP difference; all, P > .50; paired t test). Multiple linear regression analyses revealed that palpebral fissure height did not affect IOP difference for any of the tonometers. CONCLUSIONS: Simple manual UEE when measuring the IOP has little effect on the IOP obtained using all current rebound tonometers and GAT.

Mechanoluminescent Visualization of Crack Propagation for Joint Evaluation.

In this study, methods for the mechanoluminescent (ML) visualization of crack propagation and mechanical behavior to evaluate adhesive joints are demonstrated and explained. The first step involved sample preparation; an air spray was used to apply ML paint to the surface of the adhesive joint specimens. The performance of the ML sensor was described to examine the measurement conditions. The results of ML sensing during a double cantilever beam (DCB) test and a lap-shear (LS) test are demonstrated as these are the most frequently and widely used methods for evaluating adhesives. Originally, it was difficult to directly quantify the crack tip and strain/stress distribution and concentration because the crack tip was too small, and the effects of the strain could not be observed. The mechanoluminescence, crack propagation, and mechanical behavior during mechanical testing can be visualized via the ML pattern during the adhesive evaluation. This allows for the recognition of the precise position of the crack tips and other mechanical behaviors related to structural failure.

Potentiometric-Type Gas Sensor Using MgFe2O4 Sensing Electrode for Detection of Hydrocarbon Based on Carbon Number.

Hydrocarbon (HC) monitoring is necessary for safe and effective operations in industries such as petroleum and gas. In this study, total hydrocarbons can be detected by using yttria-stabilized zirconia (YSZ)-based potentiometric-type gas sensor using MgFe2O4 sensing electrode (SE). The sensor was found to generate a similar response magnitude to those of hydrocarbons that have the same carbon number, irrespective of the type of carbon bond (total hydrocarbon detection). Aside from being capable of detecting total hydrocarbons sensitively and selectively with rapid response time, the sensor using MgFe2O4-SE also exhibited a linear relationship between sensor responses and carbon number. In addition to that, the developed sensor showed a logarithmically linear relationship between sensor responses and HC concentration in the range 20-700 ppm. These sensing characteristics were confirmed to be reproducible, and sensor responses toward HC were found to be repeatable and gradually decreased with increasing in O2 concentration in the range of 3-21 vol %.

Effect of phosphoric acid and sodium hydroxide on cleaning and bonding of saliva-contaminated feldspar porcelain.

Purpose Hydrofluoric acid has been used to remove salivary contamination in dental glass-ceramics before bonding treatment. However, alternative methods are required because hydrofluoric acid is harmful. This study examined the cleaning effects of phosphoric acid and sodium hydroxide on glass-ceramics for bonding pre-treatment.Methods Feldspar porcelain was divided into four groups: (C) cleaned porcelain without any contamination, (S) porcelain contaminated with saliva, (SPA) porcelain cleaned with 37% phosphoric acid after saliva contamination, and (SSH) porcelain cleaned with 10% sodium hydroxide after saliva contamination. Each sample was bonded to the resin cement using a silane-containing primer. They were then subjected to a shear bond strength (SBS) test. Each surface was analyzed by scanning electron microscopy (SEM), contact angle measurements, and Fourier transform infrared spectroscopy (FT-IR).Results The SBS of group SSH was comparable to that of group C but significantly higher than that of groups S and SPA. SEM observations showed that saliva-like structures remained on the samples of groups S and SPA, but not on the SSH group. The contact angles of groups C and SSH were comparable and significantly smaller than those of groups S and SPA, respectively. FT-IR analysis also revealed saliva in groups S and SPA, which was absent in the SSH group.Conclusions The saliva remained on the porcelain even after cleaning with phosphoric acid, and SBS was not restored to the same level as before the contamination. In contrast, sodium hydroxide eliminated saliva and restored SBS to the same level as before contamination.

Construction of sensitive and selective zirconia-based CO sensors using ZnCr2O(4)-based sensing electrodes.

The carbon monoxide (CO) sensitivity of a mixed-potential-type yttria-stabilized zirconia (YSZ)-based tubular-type sensor utilizing a ZnCr(2)O(4) sensing electrode (SE) was tuned by the addition of different precious metal nanoparticles (Ag, Au, Ir, Pd, Pt, Ru and Rh; 1 wt % each) into the sensing layer. After measuring the electromotive force (emf) response of the fabricated SEs to 100 ppm of CO against a Pt/air-reference electrode (RE), the ZnCr(2)O(4)-Au nanoparticle composite electrode (ZnCr(2)O(4)(+Au)-SE) was found to give the highest response to CO. A linear dependence on the logarithm of CO concentration in the range of 20-800 ppm at an operational temperature of 550 °C under humid conditions (5 vol % water vapor) was observed. From the characterization of the ZnCr(2)O(4)(+Au)-SE, we can conclude that the engineered high response toward CO originated from the specific properties of submicrometer sized Au particles, formed via the coalescence of nanosized Au particles located on ZnCr(2)O(4) grains, during the calcining process at 1100 °C for 2 h. These particles augmented the catalytic activities of the gas-phase CO oxidation reaction in the SE layer, as well as to the anodic reaction of CO at the interface; while suppressing the cathodic reaction of O(2) at the interface. In addition, the response of the ZnCr(2)O(4)(+Au)-SE sensor toward 100 ppm of CO gradually increased throughout the 10 days of operation, and plateaued for the remainder of the month that the sensor was examined. Correlations between SEM observations and the CO sensing characteristics of the present sensor were suggestive that the sensitivity was mostly affected by the morphology of the Au particles and their catalytic activities, which were in close proximity to the ZnCr(2)O(4) grains. Furthermore, by measuring the potential difference (emf) between the ZnCr(2)O(4)(+Au) and a ZnCr(2)O(4) electrode, sensitivities to typical exhaust component gases other than CO were found to be negligible at 550 °C.

Surface modification of feldspar porcelain by corona discharge and its effect on bonding to resin cement with silane coupling agent.

This study aims to develop a corona discharge process for a surface treating a glass-ceramic, feldspar porcelain, to improve its bonding to a resin cement with a silane-coupling agent. Corona discharge, a type of plasma process, was performed using a custom-made device on a porcelain surface at temperatures ranging from 25 to 300 °C, for specific treatment times in air. The porcelain was then subjected to a post-heat-treatment at 600 °C to condition the surface state. The resulting surface was primed with a silane-coupling-agent followed by cementing using a resin cement to measure the shear bond strength (SBS). To investigate the effect of surface modifications by the corona discharge treatment, the porcelain was characterized by surface roughness, contact angle, and an X-ray photoelectron spectroscopy analyses. The SBS for the corona-discharge-treated porcelain increased with an increase in treatment-temperature and -time, and reached the maximum value at 200 °C and 5 min. The post-heat-treatment improved the bond durability after thermocycling. The SBS for the corona-discharge-treated porcelain was then compared to that of a conventional hydrofluoric-acid-treated one, which showed that the SBSs were comparable. The results of the surface characterizations indicated that the corona discharge treatment generated silanol groups on the porcelain surface giving hydrophilic properties without roughening the surface. It was found that the corona discharge treatment generates silanol groups on the porcelain surface, resulting in an increased SBS. This study is the first to demonstrate that corona discharge treatment is effective for improving bond strength through the modification of the surface of glass-ceramics.

Adhesive bonding of alumina air-abraded Ag-Pd-Cu-Au alloy with 10-methacryloyloxydecyl dihydrogen phosphate.

The aim of this paper is to study changes in the Ag-Pd-Cu-Au alloy surfaces by alumina air-abrasion process and effect of those changes on the adhesive bonding characteristic. Surface roughness, surface composition and chemical state of the alumina air-abraded alloys were analyzed by a confocal laser scanning microscope, an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy. The results showed that the alumina air-abrasion changed the alloy surface by mechanical roughening, alumina remain and copper oxidation. Effect of the changes in the alloy surface on the adhesive bonding characteristic was examined by using a methyl methacrylate/tri-n-butylborane derivative (MMA/TBB) resin cement with the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained primer. The shear bond strength test results indicated that the surface oxidation by the abrasion is the main contributor that improved the adhesive bonding rather than other effects such as mechanical roughening or alumina remain.

Chemical alteration of Ag-Pd-Cu-Au alloy surface by alumina air-abrasion and its effect on bonding to resin cement.

The goal of this study was to investigate the chemical alteration of a dental alloy surface by alumina air-abrasion and its effect on bonding to resin cement. Alumina air-abrasion was carried out on an Ag-Pd-Cu-Au alloy. The surface morphology and chemical state of the abraded alloy were characterized. The effect of the air-abrasion on the shear bond strength between the alloy and a methyl methacrylate/tri-n-butyl borane (MMA/TBB) resin cement with some primers was evaluated. The surface characterization revealed that the alumina air-abrasion mechanically roughened and chemically altered the surface. The chemical alterations had two effects: (1) abraded alumina particles remained on the alloy surface and (2) copper ions were oxidized in the alloy surface. As the result, the shear bond strength test indicated that 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained primer worked with the abraded alloy surface, whereas it did not work with the non-abraded alloy surface.

Comparison of the Intraocular Pressure Measured Using the New Rebound Tonometer Icare ic100 and Icare TA01i or Goldmann Applanation Tonometer.

PURPOSE: We evaluated the agreement between the intraocular pressure (IOP) values of new rebound tonometer, Icare ic100, and Icare TA01i or Goldmann applanation tonometer (GAT). METHODS: We studied one eye each of 106 subjects (57 with primary open-angle glaucoma, 49 healthy subjects). IOP was randomly measured twice with the patient in sitting position using the Icare ic100, Icare TA01i, and GAT. Tonometer measurements were evaluated using Bland-Altman analysis. The relationship between IOP difference (Icare ic100-GAT) and age, sex, disease, axial length, central corneal thickness (CCT), and corneal curvature was investigated using multivariate regression analysis. RESULTS: IOPs measured using Icare ic100, Icare TA01i, and GAT were 11.7±3.0 (mean±standard deviation), 12.2±2.9, and 16.0±3.2 mm Hg, respectively (P<0.001, one-way analysis of variance). Icare ic100 showed significantly lower IOPs than GAT (P<0.05), but not than Icare TA01 (P>0.05; Tukey-Kramer test). Bland-Altman analysis revealed that the mean differences between Icare ic100 and Icare TA01i and those between Icare ic100 and GAT were -0.46 and -4.2 mm Hg, respectively (95% limits of agreement, -3.35 to 2.42 and -10.10 to 1.61 mm Hg, respectively). For IOP differences between Icare ic100 and GAT, parameters selected in the optimal model were CCT (coefficient, 20.3, P=0.029), corneal curvature (3.0, P=0.020), and glaucoma-normal (-1.0, P=0.004). CONCLUSIONS: The new rebound tonometer Icare ic100 almost constantly showed IOPs lower than GAT. The difference was affected by CCT, corneal curvature, and disease.

Iris Morphological Features in Patients with 360° Angle-Closure Neovascular Glaucoma: An Anterior Segment Optical Coherence Tomography Study.

PURPOSE: To investigate iris morphological features in 360° angle-closure neovascular glaucoma (NVG) by swept-source anterior segment optical coherence tomography (ASOCT). PATIENTS AND METHODS: In this retrospective, clinic-based, comparative study, 14 patients with 360° angle-closure NVG and 14 healthy age-matched control subjects were enrolled. All patients enrolled had no prior glaucoma surgery but underwent cataract surgery with intraocular lens implantation. Horizontal scanning images of swept-source ASOCT were analyzed using software calipers in temporal and nasal angle areas. The iris thickness at 1 and 2 mm from the pupil edge, iris length, trabecular meshwork length, peripheral anterior synechia (PAS) length, PAS height ratio (PAS length/trabecular meshwork length), and pupil diameter were measured. RESULTS: Between the groups, there were no statistically significant differences in iris length, trabecular meshwork length, and pupil diameter (p > 0.05). However, the iris thickness was significantly reduced in the NVG group compared with the control group in the temporal and nasal areas (0.306 vs. 0.563 mm/0.326 vs. 0.645 mm at 1 mm, 0.278 vs. 0.523 mm/0.282 vs. 0.546 mm at 2 mm, respectively) (mean, all p < 0.001). In the NVG group, PAS height ratios were 1.55 ± 0.45 (mean ± standard deviation) (range, 0.58-2.30) and 1.55 ± 0.78 (range, 0.68-3.68) at the temporal and nasal angles, respectively. CONCLUSIONS: In patients with 360° angle-closure NVG, the iris thickness decreased to about 50% of that in healthy subjects, and the PAS length exceeded the trabecular meshwork length by about 1.5 times.

YSZ-based sensor using Cr-Fe-based spinel-oxide electrodes for selective detection of CO.

A selective carbon monoxide (CO) sensor was developed by the use of both of CuCrFeO4 and CoCrFeO4 as the sensing electrode (SE) for yttria-stabilized zirconia (YSZ)-based potentiometric sensor. The sensing-characteristic examinations of the YSZ-based sensors using each of spinel oxides as the single-SE sensor showed that CuCrFeO4-SE had the ability to detect CO, hydrocarbons and NOx gases, while CoCrFeO4-SE was sensitive to hydrocarbons and NOx gases. Thus, when both SEs were paired as a combined-SEs sensor, the resulting sensor could generate a selective response to CO at 450 °C under humid conditions. The sensor was also capable of detecting CO in the concentration range of 20-700 ppm. Its sensing mechanism that was examined via polarization-curve measurements was confirmed to be based on mixed-potential model. The CO response generated by the combined-SEs sensor was unaffected by the change of water vapor concentration in the range of 1.3-11.5 vol% H2O. Additionally, the sensing performance was stable during 13 days tested.

Cataract surgery causes biomechanical alterations to the eye detectable by Corvis ST tonometry.

PURPOSE: Modern cataract surgery is generally considered to bring about modest and sustained intraocular pressure (IOP) reduction. However, the pathophysiological mechanism for this remains unclear. Moreover, a change in ocular biomechanical properties after surgery can affect the measurement of IOP. The aim of the study is to investigate ocular biomechanics, before and following cataract surgery, using Corvis ST tonometry (CST). PATIENTS AND METHODS: Fifty-nine eyes of 59 patients with cataract were analyzed. IOP with Goldmann applanation tonometry (IOP-G), axial length, corneal curvature and CST parameters were measured before cataract surgery and, up to 3 months, following surgery. Since CST parameters are closely related to IOP-G, linear modeling was carried out to investigate whether there was a change in CST measurements following cataract surgery, adjusted for a change in IOP-G. RESULTS: IOP-G significantly decreased after surgery (mean±standard deviation: 11.8±3.1 mmHg) compared to pre-surgery (15.2±4.3 mmHg, P<0.001). Peak distance (the distance between the two surrounding peaks of the cornea at the highest concavity), maximum deformation amplitude (the movement of the corneal apex from the start of deformation to the highest concavity) and A1/A2 velocity (the corneal velocity during inward or outward movement) significantly increased after cataract surgery (P<0.05) while radius (the central curvature radius at the highest concavity) was significantly smaller following cataract surgery (P<0.05). Linear modeling supported many of these findings, suggesting that peak distance, maximum deformation amplitude and A2 velocity were increased, whereas A2 deformation amplitude and highest concavity time were decreased (after adjustment for IOP change), following cataract surgery. CONCLUSION: Corneal biomechanical properties, as measured with CST, were observed to change significantly following cataract surgery. TRIAL REGISTRATION: Japan Clinical Trials Registry UMIN000014370.

Time Course of Conjunctival Hyperemia Induced by a Rho-kinase Inhibitor Anti-glaucoma Eye Drop: Ripasudil 0.4.

PURPOSE: We investigated the detailed time course of conjunctival hyperemia induced by ripasudil 0.4%, a novel Rho-kinase inhibitor anti-glaucoma eye drop, in healthy subjects. METHODS: We recruited 51 healthy subjects and administered ripasudil 0.4% in their right eye. We evaluated conjunctival hyperemia using slit lamp photography and measured the intraocular pressure (IOP) using the Icare PRO Rebound Tonometer at baseline and after 5, 15, 30, 60, 90, and 120 min. The conjunctival hyperemia score was graded by three independent observers on a scale of 0 (none) to 3 (severe). Additionally, we analyzed the "percent coverage" of conjunctival hyperemia by using an automated hyperemia analysis software program; this program provides the pixel coverage of the conjunctival vessels in the region of interest. Dunnett and Steel multiple comparison tests were used, as appropriate, for the subsequent analyses. RESULTS: The conjunctival hyperemia score and percent coverage increased rapidly after the instillation of ripasudil 0.4%, peaking at 15 min (score: 1.83 ± 0.29 [mean ± SD]) and 5 min (11.6% ± 4.7%), respectively, and then gradually decreasing until 120 min (0.45 ± 0.22 and 4.7% ± 1.8%, respectively), when they reached a level that was not significantly different from the baseline values. The IOP decreased significantly compared to the baseline at 30, 60, and 90 min, based on the Dunnett test. CONCLUSION: Conjunctival hyperemia induced by ripasudil 0.4% peaks rapidly to moderate severity, but subsides relatively quickly.

A Pilot Evaluation Assessing the Ease of Use and Accuracy of the New Self/Home-Tonometer IcareHOME in Healthy Young Subjects.

PURPOSE: We investigated the ease of use and accuracy of a new self/home-tonometer (IcareHOME) versus Goldmann applanation tonometry (GAT) and the Icare tonometer (Icare) by measuring the diurnal intraocular pressure (IOP). PATIENTS AND METHODS: The right eyes of 43 healthy young subjects were studied. The IOP was measured using the IcareHOME, GAT, and Icare 6 times a day, every 2 hours, from 8:00 to 18:00. The coincidence of the diurnal curves among all tonometers was analyzed using a linear mixed model. The intradevice and interdevice agreement was evaluated using the intraclass correlation coefficients (ICC) and Bland-Altman method. The subjects' perception of the IcareHOME was evaluated using a questionnaire. RESULTS: The liner mixed model showed similar diurnal IOP curves for all tonometers (P=0.543); however, significant differences were observed between the tonometers over time (P<0.001). The intradevice repeatability was ICC>0.8 among all tonometers, although the interdevice agreement was lowest between the IcareHOME and GAT (ICC=0.641). The IOP values were significantly lower for the IcareHOME than for the GAT at 12:00, 16:00, and 18:00 (P<0.05, Tukey-Kramer test). The mean differences between the Icare and IcareHOME and GAT and IcareHOME were 0.83 and 1.03 mm Hg, respectively (95% limit of agreement: -4.17 to 5.84 mm Hg and -3.91 to 5.98 mm Hg, respectively). Regarding the subjects' perception of handling the IcareHOME, 17 (39.5%) subjects answered "easy to use," 20 (46.5%) answered "normal," and six (13.9%) answered "difficult to use." CONCLUSIONS: The IcareHOME can be used as a self/home-tonometer; however, it may result in lower IOP values.

Prostaglandin-associated periorbitopathy in latanoprost users.

PURPOSE: We investigated the incidence of prostaglandin-associated periorbitopathy (PAP) in subjects with glaucoma treated with latanoprost ophthalmic solution. SUBJECTS AND METHODS: One eye and the forehead in 22 subjects were evaluated. All patients had used latanoprost for more than 1 year (range, 12 to 45 months; mean, 26.0 months) and were prostaglandin F2α analogue treatment-naïve. Digital photographs of the subjects obtained before latanoprost therapy and at the last examination were compared retrospectively. Four signs of PAP (deepening of the upper eyelid sulcus (DUES), upper eyelid ptosis, flattening of the lower eyelid bags, and inferior scleral show) and supplemental side effects around the eyelids (eyelash growth, poliosis, and eyelid pigmentation) were judged to be negative or positive by three independent observers. If the observers unanimously rated a sign as positive, the result was defined as positive. RESULTS: Twelve subjects (54.5%) had no apparent signs. Three subjects were judged to have DUES (13.6%), and two subjects each were judged to have flattening of the lower eyelid bags and eyelid pigmentation (9.0%). The other signs were judged as positive in only one subject each, respectively (4.5%). A univariate logistic regression analysis showed no significant associations between any of the signs and age, sex, or the duration of therapy. CONCLUSION: Latanoprost induced DUES, upper eyelid ptosis, flattening of the lower eyelid bags, inferior scleral show, and supplemental side effects around the eyelids; however, the rates of such occurrence might be relatively low.

Stabilization of sensing performance for mixed-potential-type zirconia-based hydrocarbon sensor.

The recently reported sensing characteristics of the mixed-potential-type yttria-stabilized zirconia (YSZ)-based hydrocarbon (HC) sensor attached with ZnCr(2)O(4)-sensing electrode (SE) were found to be changed after the 10-day operation at 550°C under the wet condition (5 vol.% water vapor). To improve the stability of the present sensor, the several modifications of the SE material by adding YSZ powder were examined. As a result, the sensor using the laminated (ZnCr(2)O(4)/YSZ)-SE gave the stable electromotive force (emf) response against 100 ppm C(3)H(6) at 550°C for about one month examined. Based on the scanning electron microscopy (SEM) observation and the AC complex-impedance measurements, it was concluded that the stable behavior of the sensor using the laminated (ZnCr(2)O(4)/YSZ)-SE was provided by the stabilization of the interface between ZnCr(2)O(4) grains and YSZ particles. The fabricated sensor exhibited the linear dependence of sensitivity on the logarithm of either C(3)H(6) concentration (in the range of 20-800 ppm) or mixtures of various hydrocarbons (HCs) (in the range of 90-2600 ppmC). In addition, the emf response was not altered by the change of O(2) (2-20 vol.%), H(2)O (0-10.8 vol.%) and CO(2) (0-20 vol.%) concentrations, and no interference of other gases (CO, NO, NO(2), H(2), and CH(4)) was observed.

Spontaneous gradual accumulation of hexagonally-aligned nano-silica on gold nanoparticles embedded in stabilized zirconia: a pathway from catalytic to NH3-sensing performance.

The present study highlights the influence of nano-impurities on the catalytic/sensing performance of nano-structured Au sensing-electrodes (SEs) housed in a quartz reactor and operated at high temperature over a long period of time. The planar sensor, made from a nano-structured Au-SE on a polished-polycrystalline (pp) yttria-stabilized zirconia (YSZ) substrate exhibited initially negligible electromotive force (emf) response to each of the examined gases (CO, CH(4), C(3)H(8), C(3)H(6), NO(x) and NH(3); 400 ppm each) at 700 °C in the presence of 5 vol.% oxygen and 5 vol.% water vapor. Such a poor emf response was attributed to the excellent gas-phase oxidation/reduction ability of Au nanoparticles embedded in the YSZ substrate at high temperature. The response of the planar sensor made up of nano-structured Au-SE was monitored for about 75 days at 700 °C. As a result of this long-term monitoring, we detected the appearance of highly sensitive and selective NH(3) gas-sensing properties after 45-75 days of sensor operation. Detailed observation of the morphology and composition of the as-fabricated nano-structured Au-SE after 75 days operation at 700 °C revealed the gradual accumulation of hexagonally-aligned SiO(2) nano-impurities on the surface of the Au nanoparticles. The NH(3) sensing mechanism of the YSZ-based sensor using the spontaneously-formed composite (nano-Au + nano-SiO(2))-SE is therefore proposed to be based on a strong acid-base interaction between gaseous NH(3) and SiO(2) nano-impurities, followed by spillover of adsorbed NH(3) towards the nano-Au/pp-YSZ interface.