The fluorescence intensity ratio technique for optical fiber-based point temperature sensing is reviewed, including the materials suitable for this technique. The temperature dependence of the fluorescence intensity ratio has been studied using thermally coupled energy levels in seven different rare earth ions doped into a variety of glasses and crystals. Sensor prototypes developed using Pr3+:ZBLANP, Nd3+-doped silica fiber and Yb3+-doped silica fiber as the sensing material have been used to measure temperatures covering the range of approximately −50 to 600 °C with a resolution of the order of 1 °C.

Articles you may be interested inCharacteristics of doped optical fiber for fluorescence-based fiber optic temperature systems Rev. Sci. Instrum. 74, 5212 (2003); 10.1063/1.1623624 Analysis of dopant concentration effects in praseodymium-based fluorescent fiber optic temperature sensors Rev. Sci. Instrum. 71, 100 (2000)Nd 3+ -doped optical fiber temperature sensor using the fluorescence intensity ratio technique Rev. Sci. Instrum. 70, 4279 (1999); 10.1063/1.1150067 Determination of local high temperature excursion in an intrinsic doped fiber fluorescence-based sensor Rev. Sci. Instrum. 69, 2930 (1998); 10.1063/1.1149036Quasidistributed fluorescence-based optical fiber temperature sensor system Rev.The performance of the two most promising fluorescence-based temperature sensing techniques, namely the fluorescence intensity ratio ͑FIR͒ and fluorescence lifetime ͑FL͒ schemes, have been compared. Theoretical calibration graphs for the two methods illustrate the useful monotonic change of the response with temperature variation. Comparison of the responses and the sensitivities of the two schemes show that at very low temperatures the FIR method exhibits a significant variation with temperature, while the response of the FL method becomes constant with its sensitivity approaching zero. With increasing temperature, the FIR and the FL methods ͑with short relaxation times and shorter intrinsic lifetimes of the upper energy levels͒ share a similar sensitivity over a wide temperature range. The presence of a long relaxation time or a longer intrinsic lifetime of the upper level in the use of the FL method gives a less satisfactory response. Experimental data obtained for a range of dopant ions in various host materials are found to be consistent with the theoretical expectation, with each material having a specific energy gap difference. The sensitivities of each material are compared graphically which would allow the most appropriate sensor for an intended application to be selected.

No abstract

Atomic force microscopy has been used to study the in situ adsorption of an amphiphilic block copolymer from aqueous solution onto hydrophilic mica and hydrophobic silica substrates. Adsorption was studied as a function of concentrationsclose to and below the bulk critical micelle concentration the copolymers adsorb as single chains or "premicelle aggregates". As concentration is increased, micelles form into densely packed structures. At a given concentration, the ordering is higher for the strongly adsorbed micelles on silica. Competitive adsorption onto the hydrophilic silicon nitride AFM tip occurs. The substrate coverage of micelles on mica increases roughly linearly with scan time at low micelle concentration. Weak adsorption on mica was analyzed to provide a two-dimensional diffusion coefficient. The effect of tip oscillation frequency on the AFM images was investigatedshigher frequencies were required to image polymer aggregates on mica. Finally, force-distance curves provide information on the nanomechanical properties of the adsorbed polymer layers. Evidence is presented to show that micelles and aggregates adsorb to silica via the hydrophobic P block, while they adsorb to mica via the hydrophilic E block.

Physical delivery of anticancer drugs in controlled anatomic locations can complement the advances being made in chemo‐selective therapies. To this end, an optical fiber catheter is coated in a thin layer of metal organic framework UiO‐66 and the anticancer drug 5‐Fluorouracil (5‐FU) is deposited within the pores. Delivery of light of appropriate wavelength through the fiber catheter is found to trigger the release of 5‐FU on demand, offering a new route to localized drug administration. The system exhibits great potential with as much as 110 × 10−6 m of 5‐FU delivered within 1 min from one fiber.