Optical Fibre NO2 Sensor Based on Lutetium Bisphthalocyanine in a Mesoporous Silica Matrix

Abstract

In this article, we describe a NO2 sensor consisting of a coating based on lutetium bisphthalocyanine (LuPc2) in mesoporous silica. The sensor exploits the absorption spectrum change of this material which strongly and reversibly decreases in contact with NO2. NO2 is measured by following the amplitude change in the reflected spectrum of the coating deposited on the tip of a silica fibre. As diffusion of NO2 in LuPc2 is slow, the response time could be slow. To reduce it, the active molecules are dispersed in a mesoporous silica matrix deposited by a sol-gel process (Evaporation Induced Self Assembly) avoiding the formation of large crystals. Doing so, the response is fairly fast. As the recovery is slow at room temperature, the recovery time is reduced by exposure to UV light at 365 nm. This UV light is directly introduced in the fibre yielding a practical sensor sensitive to NO2 in the ppm range suitable for pollution monitoring.

Higly sensitive active medium of sensor NO2 , based on cholesteric nematic mixture with impurities of carbon nanotubes

“…The spectral characteristics and its changes under the action of nanocomposites based on HLC doped with carbon nanotubes tracked by the signal converter optical sensor. The main problem of creating signal converter of optical sensors discussed in work [24][25][26][27][28][29].…”

Multifunctional integration on optical fiber tips: challenges and opportunities

“…Further, nanomaterials including metals, metal oxides, their composites, as well as low-dimensional materials such as CNT, graphene, and graphene oxides have been implemented for fiber-optic physical, chemical, and biological sensors. 15,117,118,127,128,159,[214][215][216][217][218][219][220][221][222][223][224][225] Incorporating the principles of Fresnel reflection, interferometers, and surface plasmon resonance (SPR), respectively, various nanomaterial films have been integrated onto fiber tips, thus demonstrating chemical sensors tailored to the detection of specific gases, VOCs, and heavy metal ions. 15,214,226 Predominantly, these fiber-based sensors exploit the sensing characteristics of the nanomaterials, which eventually affect the optical structure of the optical fiber sensing system.…”

“…Within the last decade, toxic gases (e.g., NH 3 , H 2 S, NO 2 , CO 2 ) and flammable gases (e.g., CH 4 , H 2 ) have been monitored using these optical fiber-based chemical sensors that comprise sensitive nanomaterial films on fiber tips. [215][216][217][218][219][220][221][222][223][224] For example, nanofilms of graphene oxide (GO)-based nanohybrids and porous graphene, as well as Fe 3 O 4 -graphene composite-coated optical fiber tips, have been investigated for the detection of ammonia (NH 3 ) at room temperature. 222,223,227 Elsewhere, ZnO NPs have been embedded into a poly-methyl-methacrylate (PMMA) matrix and coated on the fiber tip for sensing H 2 S (at concentrations ranging from 1 to 5 ppm) at room temperature.…”

“…221 Furthermore, a lutetium bisphthalocyanine (LuPc 2 ) dispersed mesostructured silica film has been coated on a fiber tip, which was sensitive to NO 2 in the ppm range. 224 Sensitive layers of Pd, Pd-Y, Pt-WO 3 , Pd capped alloys, and nanostructured α-MoO 3 [Fig. 11(a)] have been coated both on fiber endfaces and fiber resonance structures, creating high sensitivity hydrogen sensors.…”