Microscale enzymatic optical biosensors using mass transport limiting nanofilms. 1. Fabrication and characterization using glucose as a model analyte

"Smart tattoo" sensors-fluorescent microspheres that can be implanted intradermally and interrogated noninvasively using light-are being developed as potential tools for in vivo biochemical monitoring. In this work, a platform for enzymatic tattoo-type sensors is described and prototype devices evaluated using glucose as a model analyte. Sensor particles were prepared by immobilizing Pt(II) octaethylporphine (PtOEP), a phosphorescent dye readily quenched by molecular oxygen, into hybrid silicate microspheres, followed by loading and subsequent covalent immobilization of glucose oxidase. Rhodamine B-doped multilayer nanofilms were subsequently assembled on the surfaces of the particles to provide a reference signal and provide critical control of glucose transport into the particle. The enzymatic oxidation of glucose within the sensor results in the glucose concentration-dependent depletion of local oxygen levels, enabling indirect monitoring of glucose by measuring relative changes in PtOEP emission. A custom testing apparatus was used to monitor the dynamic sensor response to varying bulk oxygen and glucose levels, respectively. For the prototypes tested, dynamic test results indicate that the sensors respond rapidly (t(95) = 84 s) and reversibly to changes in bulk glucose levels, while demonstrating high baseline stability. The sensitivity (change in intensity ratio) of these devices was determined to be 4.16 +/- 0.57%/mg dL(-1). The analytical range for the prototypes was determined to be 2-120 mg/dl, though this can be extended to cover the physiologically relevant range by tailoring the nanofilm coatings. These findings confirm the potential for enzymatic microscale optical and pave the way for extension of this initial demonstration with glucose to target other biochemical species relevant to metabolic monitoring.     

磁控溅射制备纳米二氧化钒半导体薄膜及表征

本文采用射频磁控溅射法,结合氩气气氛退火工艺制备了VO2薄膜。通过优化磁控溅射和热退火工艺,结合激光拉曼光谱仪(Raman)、X射线光电子能谱(XPS)、电镜扫描(SEM)对薄膜的相结构、组分和表面形貌进行分析。结果表明:溅射衬底温度为150℃,在450℃氩气气氛退火2.5 h能制备出高质量的VO2薄膜,表面呈米粒状,有一定的取向性。     

Effects of composition on optical and electrical properties of amorphous In-Ga-Zn-O films deposited using radio-frequency sputtering with varying O2 gas flows

This study used powders containing various In₂O₃-Ga₂O₃-ZnO (IGZO) chemical compositions to manufacture targets by using a metallurgical process. The resulting targets were used to deposit amorphous In-Ga-Zn-O (a-IGZO) channel films using a radio frequency (r.f.) magnetron sputtering process. The average transmittance increased and achieved saturation; the resistivity increased in conjunction with the O₂ flow ratio of less than 6%; and subsequently, the resistivity decreased with increasing the O₂ flow ratio larger than 6%. This study examined the effects of compositions on electrical characteristics and optical properties of a-IGZO films at varied O₂ flow rates. The effects of composition on optical and electrical characteristics of a-IGZO films indicate that the average transmittance of a-IGZO films with more zinc atoms (approximately 50%) had more than 80% at various O₂ flow ratios because of the higher oxygen absorption of the zinc atoms. However, the average transmittance of a-IGZO film with a lower zinc atomic ratio (approximately 20%) without an O₂ flow ratio decreased to below 10% because of the indium and indium oxide crystalline precipitation in the indium-rich a-IGZO films. The results revealed that the resistivity increased when the gallium atomic ratio increased and the indium atomic ratio decreased.     

Electrical and optical properties of MoSe2 films prepared by r.f. magnetron sputtering

The electrical resistivity of MoSe₂ films prepared by r.f. magnetron sputtering was measured between 300 and 10 K. The main sputtering parameter governing the physical properties of the films was found to be the substrate temperature T_sub. The room temperature resistivity of the as-sputtered films increased from $\text{1.7 × 10}{}^{-1}\text{Ω}\text{cm}$(T_sub = -70 °C) to $\text{1.4 × 10}{}^1\text{Ω}\text{cm}\text{(T}{}_{\mathrm{<mtext>sub</mtext>}}\text{= 150 °}\text{C}\text{)}$. A check of the thermo-electrical response showed that the majority charge carriers are holes except for films deposited at T_sub = 150 °C which are n type. Hall effect measurements indicated very low Hall mobilities (3–5 cm² V^-1 s^-1). Thermal annealing increased the room temperature resistivities by more than one order of magnitude for the specimens sputtered at a low substrate temperature. The optical properties were weakly influenced by the process conditions. The optical gap was determined to be 1.06 eV.     

Microstructure and optical properties of Al2O3 prepared by oblique deposition using microsphere shell templates

We fabricated an orderly inclined Al2O3 column array using a hollow microsphere template. The microstructure and optical properties were investigated with scanning electron micrography and a UV/VIS spectrometer, respectively. Microsphere shell templates were formed using atomic layer deposition to prevent the melting of polystyrene microspheres during the following high-temperature deposition process. An inclined Al2O3 column array with a 30° tilt angle was grown by oblique deposition on a substrate with a 75.5° tilt angle with respect to the substrate normal. Birefringence and photonic crystalline behavior can be observed in the orderly inclined column array. The difference in the refractive indices between the p and s polarizations of the orderly inclined Al2O3 column array was about 0.1. The photonic properties of the crystal were enhanced compared to those of substrates without patterns.     

Influence of heat treatment on the optical properties of SnO2 : Sb thin films deposited by dip coating using aqueous solution

Antimony doped tin oxide thin films were deposited on glass by a chemical route derived from Pechini method. Particular emphasis was given to the microstructure of crystallized films. Crystalline phase formation was studied by grazing incident X-ray diffraction and by thermal analyses. Scanning electron microscopy was carried out for microstructure characterization, surface roughness was observed using scanning tunneling microscope and the optical transmittance measurements were performed in the wavelength range of 200–800 nm.     

Influence of deposition parameters on the optical and structural properties of TiO2 films produced by reactive d.c. plasmatron sputtering

We investigated the variations in the structure and optical properties of TiO₂ films produced by reactive d.c. plasmatron sputtering with the most important deposition parameters.Over a wide range, the phase composition (ratio of rutile to anatase) and the grain size of the TiO₂ films can be influenced in a controlled manner by variations in the substrate temperature and the oxygen partial pressure.Because of their high refractive index and low light-scattering losses, plasmatron-sputtered TiO₂ films are of great interest in the field of optical interference coatings, e.g. for dielectric multilayer stacks.     

Fabrication and optical properties of Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) thin films on Si substrates using the PLD method.

Epitaxial 0.67Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3)-0.33PbTiO(3) (PMN-PT) thin films with electro-optic effects were fabricated on (PMN-PT) thin films with electro-optic effects were fabricated on (La0(0.5)Sr0(0.5))CoO(3) (LSCO)/CeO(2)/YSZ-buffered Si(001) substrates using double-pulse excitation pulsed laser deposition (PLD) method with a mask placed between the target and the substrate. Epitaxial growth of PMN-PT thin films was undertaken using the two-step growth method of PMN-PT film. The PMN-PT seed layer was deposited at 500 degrees C on the LSCO/CeO(2)/YSZ/Si, which temperature was the same as that used for LSCO deposition. The PMN-PT thin films were deposited on the PMN-PT seed layer at 600 degrees C, which enables growth of high-crystallinity PMN-PT films with smooth surfaces. We obtained optimum fabrication conditions of PMNPT film with micrometer-order thickness. Resultant films showed high crystallinity with full width at half maximum (FWHM) = 0.73 deg and 1.6 mum thickness. Electro-optic properties and the refractive index value were measured at 633 nm wavelength using the prism coupling method. The obtained refractive index was 2.59. The electro-optic coefficients r(13) and r(33) were determined by applying the electrical field between a semitransparent, thin top electrode of Pt and a bottom LSCO electrode. The electro-optic coefficient was r(13) = 17 pm/V at transverse electric field (TE) mode and r(33) = 55 pm/V at transverse magnetic field (TM) mode.