In the temperature range of 296K-673K, the optical temperature sensors based on Er3+ doped silicate glass achieved a favorable result. Here, the operating temperature of 673K and sensitivity of 0.0023K-1, which excelled 448K and 0.004K-1 in fluoroindate glass [11], and 523K and 0.0052K-1 in chalcogendie glass [12], respectively. From Equation (2), the sensitivity depends on the ��E. Thus, the Er3+ doped silicate glass possesses a better sensitivity because its ��E of 512cm-1 is smaller than that of fluoroindate glass (��E �� 742cm-1) and chalcogendie glass (��E �� 850cm-1). The temperature resolution for the Er3+ doped silicate glass was also relatively high, at about 0.8K by employing a signal division circuitry with a precision of four digits or more.
Another important aspect to consider is the suitability of the Er3+ doped silicate glass to be fibered, and the possibility to the use the doped fiber as the active sensing element. Finally, a prototype optical high temperature sensor based on the FIR technique of the green up-conversion emissions in th
In the last years the employment of glucose oxidase (GOD) in glucose optical sensing has been largely investigated for clinical and industrial applications [1- 8]. Different immobilization procedures have been adopted [9-11] aiming to extend the linear range of optical sensors, their sensibility, specificity, reproducibility and time stability. Recently new approaches to ��in vivo�� glucose measurements by means of fluorescence-based systems have been critically reviewed by Pickup et al [12,13].
As far as concerns glucose determination by means of GOD endogenoeus fluorescence, two different approaches have been followed. The former is based on the changes in steady-state fluorescence of the flavine (FAD) region during the enzymatic reaction [14-16]. This approach is very simple and highly specific to glucose and the use of visible light (��exc = 420 nm; emission range = 480 �C 580 nm) makes it not very expensive as far as optical components. However, this approach requires large consumption of enzymes owing to the low quantum yield of flavine fluorescence. Moreover, fluorescence changes are not very strong and only particular immobilization procedures can allow a widening of linear calibration region for sensors operating in this wavelength range.
The second approach exploits the GOD UV Carfilzomib intrinsic fluorescence of some amino acids, basically tyrosine and tryptophan. This fluorescence is generally characterized by an excitation with two maxima at 224 and 278 nm and an emission around 340 nm and it is usually employed to obtain information about the enzyme configuration and bonding positions [17]. UV intrinsic fluorescence gives some advantages in comparison with flavine fluorescence: higher quantum yield and larger linear calibration range [2].