Fullerene C₆₀ immobilized in polymethylmethacrylate film as an optical temperature sensing material

Abstract

Recent years have seen a growing interest in optical sensors based on oxygen-induced or temperature-induced changes in the luminescence intensity of organic dyes [1][2][3][4]. Probes available for optical temperature sensor are fluorescent, thermal-quenchable and non oxygen-quenchable organic and inorganic dyes, such as coumarin, perylene, pyronin and rare earth metal compounds [5][6][7]. One of the candidate probes available for the optical temperature sensor is fullerene. Fullerenes possess useful electronic and photochemical properties [8][9][10]. As the fluorescence lifetime of fullerene C 60 is estimated to be 1.1 ns, the fluorescence of C 60 is not quenched by oxygen [11]. Thus, the fluorescence intensity of C 60 is changed by temperature changes. Thus, fullerene is attractive compound for optical temperature sensing based on the fluorescence intensity change thermally.In this letter we describe a new optical temperature sensing material, fullerene C 60 immobilized in polymethylmethacrylate (PMMA) film, and its temperature sensing properties. ExperimentalC 60 was obtained from Tokyo Kasei Inc. and was purified by recrystalization with toluene-benzene. PMMA (average M.W. 280 000, GPC grade) was purchased from Aldrich. The C 60 immobilized in PMMA film was formed by casting a mixture of 20 wt. % PMMA and C 60 in toluene onto 1.4 × 5.0 cm non-luminescent glass slides. The C 60 concentration in the film was approximately 1.0 × 10 -3 mol dm -3 . The films were dried at room temperature and stored in the dark prior to use. The thickness of the films was determined by the use of a micron-sensitive calliper. The thickness of the prepared film was c.a. 50 µm. The fluorescence spectrum of the C 60 film was measured using a Shimadzu RF-5300PC spectrofluorophotometer with a 150 W Xenon lamp as the excitation light source. The excitation and emission bandpasses were 10 and 5.0 nm, respectively. The sample film was mounted at a 45º angle to minimize light scattering from the sample and substrate. The temperature (260-373 K) was controlled using an Oxford Instrument Optistat-DN cryostat system. All the experiments were carried out under ambient condition.Theory of optical temperature sensing based on the fluorescence intensity change of C 60 film is as follows. The quantum yield (Φ) in the absence of quencher is given bywhere I a is the absorption intensity. k L and k D are the rate constants for the fluorescence and the radiationless deactivation, respectively. The deactivation term, k D is decomposed into a temperature-independent part k 0 and a temperature-dependent part k 1 that is related to thermally activated intersystem crossing. The k 1 can be assumed to have an Arrhenius form as follows:where A, E and R are a constant, the Arrhenius activation energy and the universal gas constant, respectively. The eq.(1) is re-written by the eq. (2) of the radiationless deactivation rate: Keyword. Optical temperature sensing -fullerene -fluorescence quenching -Arrhenius activation energy -polymer film.

Intramolecular Excimer Formation in a Tripodal Polyamine Receptor Containing Three Naphthalene Fluorophores

“…It is better than the 1%/°C value reported in ref 1 for a two component fluorescence temperature sensor and better than other systems based on the intensity of fluorescence, either dual- 17 or single-wavelength systems. [18][19][20][21][22] It also compares well with the sensitivity levels obtained with systems based on temperature-dependent excited-state lifetimes 20,23,24 and is much better than systems based on shifts in fluorescence spectra. 25 The system is not totally reversible in the temperature range tested, showing some hysteresis upon temperature cycles.…”

State of Art on Bioimaging by Nanoparticles in Hyperthermia and Thermometry: Visualization of Tissue Protein Targeting

“…Thermochromic fluorescent films and optical films are other available options [83]. Still challenge of thermal imaging remains at large for the range of milli kelvins within millisecond temporal resolution [84]. Recently several magnetic resonance image characteristics have come into light such as pH, phase contrast, spin relaxivities, etc.…”

Magnetic Nanoparticles in Cancer Diagnosis and Hyperthermic Treatment

“…The greatest limitation of temperature probes is that they provide a single-point measurement with very limited information about the temperature distribution. Various teams have reported the development of thermochromic films based on thermal fluorescence [74] or thermally sensitive optical properties [75]. These techniques have demonstrated better than 1 • C precision in laboratory tests, but the temporal response of these techniques is unclear.…”