JP5973397B2 - Electron spin resonance device - Google Patents

Description

  The present invention relates to an apparatus capable of observing an electron spin resonance (ESR) spectrum of a measurement object even in an outdoor environment.

  An ESR device is used as a device for obtaining an ESR parameter of a measurement object (see, for example, Non-Patent Document 1). ESR equipment uses free radicals such as atoms, molecules, and ions with unpaired electrons as measurement objects, and is mainly used for performance evaluation of electronic devices, dating active faults, and evaluation of radiation exposure doses to the human body. . Recently, it has been widely used for environmental evaluation such as antioxidant capacity of foods and drugs, water purification, malodor decomposition, sick house gas decomposition, decomposition of harmful substances in exhaust gas, removal of soil pollutants, and dioxin decomposition.

  A commonly used ESR device includes a microwave transmitter, a circulator, a cavity resonator, an electromagnet, a detector, and an evaluation unit.

  As the microwave transmitter, one that generates a microwave (electromagnetic wave) having a frequency of 9.5 GHz band (X-band), which is highly sensitive, is usually used. On the other hand, recently, the frequency of 1 GHz band (L-band) with less dielectric loss due to moisture has been utilized due to an increase in application to the living body and environment fields, and the present invention is also intended for application to an outdoor environment. Therefore, this frequency band is targeted. The reason for targeting the 1 GHz band is to avoid as much as possible the rise in the temperature of the sample that is the measurement object due to the heating of moisture by the microwave.

  The circulator directs the propagation direction of the microwave output from the microwave transmitter and propagating through the waveguide toward the cavity resonator side. In addition, the circulator directs the propagation direction of the microwave output from the cavity resonator and propagating through the waveguide to the detector side.

  The cavity resonator confines and resonates the microwave input from the microwave transmitter via the waveguide in the space. Such a cavity resonator is set to a size that satisfies the resonance condition of the input microwave. In addition, a sample as a measurement object is inserted into the cavity resonator in a state of being enclosed in a capillary tube.

  The electromagnet applies a DC magnetic field to a sample that is a measurement object.

  The detector detects microwave energy input from the cavity resonator through the waveguide.

  Based on the energy detected by the detector, the evaluation unit observes the ESR spectrum related to the free radical that is the measurement object, and enables qualitative and quantitative evaluation of the measurement object.

When measuring a sample which is an object to be measured using such an ESR apparatus, a microwave having a certain frequency ν ₀ output from a microwave transmitter is input to a cavity resonator through a waveguide. In this state, an external magnetic field is applied to the sample using an electromagnet. When an external magnetic field is applied to the sample, energy level splitting due to the Zeeman effect occurs in the electron spin of unpaired electrons contained in the sample (that is, degeneracy is solved), and two energy levels are formed. At this time, the difference between the two energy levels is proportional to the strength (magnetic flux density) of the external magnetic field.

When the intensity of the magnetic field is changed (magnetic field sweep) in a state where these two energy levels are formed, the microwave is generated at a specific magnetic field intensity (magnetic flux density) H ₀ corresponding to the sample as the measurement object. The energy difference due to Zeeman splitting is the same. That is, the following expression (1) is satisfied.
hν ₀ = gβH ₀ (1)

However, h is a Planck's constant (= 6.6255 × 10 ⁻³⁴ Js), g is a g value (magnetic rotation ratio) specific to the sample as a measurement object, and β is a Bohr magneton (= 9.274 × 10 ^{− 24} J / T).

  Thus, when the microwave energy and the energy difference due to Zeeman splitting coincide, a transition occurs in the state of the unpaired electron, and resonance occurs. Due to this resonance phenomenon, microwave energy is absorbed.

  That is, when the magnetic field intensity is changed (magnetic field sweep) with the microwave frequency fixed, the detector has a specific magnetic field intensity that satisfies the equation (1) according to the sample to be measured. A behavior in which the microwave energy rapidly decreases is observed as an ESR spectrum.

  When utilizing microwaves with a frequency of 1 GHz band (L-band) with low dielectric loss due to moisture, the required magnetic flux density of the magnetic field should be several tens of mT. Regardless of whether it is roughly 2, it is clearer.

"Basic knowledge of ESR", JEOL RESONANCE Inc., <http://www.j-resonance.com/knowledge/esr-basics/>

  However, the conventional ESR apparatus has a problem that it is very large in size and is not suitable for taking out to an outdoor environment. For example, the size of the cavity resonator constituting the conventional ESR device must be a size corresponding to the wavelength of the microwave (for example, a wavelength of 30 cm when the frequency is 1 GHz), that is, must be an integral multiple of a half wavelength. Therefore, it is difficult to reduce the size of the cavity resonator.

  In addition, since it is usually necessary to adjust the magnetic field strength according to the sample, electromagnets capable of adjusting the magnetic field strength are widely used. As a result, the ESR apparatus has a weight ranging from 600 kg to 2 t. Thus, the ESR device is not suitable for taking it out to the outdoor environment in terms of weight.

  As described above, the conventional ESR device requires a great deal of labor and cost because it cannot be easily carried in terms of size and weight, for example, when carrying out local environmental measurement or dating. did.

  Therefore, the present invention has been made in view of such problems, and an object thereof is to provide an ESR device that is reduced in size and weight.

The present invention relates to an electron spin resonance apparatus for observing an electron spin resonance spectrum of an object to be measured, a magnetic field applying unit for applying a magnetic field to the object to be measured, and a spiral inductor arranged so as to surround the object to be measured. Current supply means for supplying alternating current to the inductor, frequency sweep means for sweeping the angular frequency of the alternating current, and inductance measurement for measuring the inductance of the inductor for each angular frequency swept by the frequency sweep means And the inductor is covered with an insulating thin film having a dielectric loss of 0.01 or less, and the sample is disposed on the insulating thin film located inside the spiral inductor. It is a feature.
In one configuration example of the electron spin resonance apparatus of the present invention, the magnetic field applying means is a permanent magnet containing ferrite as a magnetic material.
Further, in one configuration example of the electron spin resonance apparatus of the present invention, a calculation for calculating a g value which is an electron spin resonance parameter based on a resonance angular frequency observed from a change in inductance measured by the inductance measuring means is further performed. Means are provided.

  According to the present invention, since the electron spin resonance spectrum of the measurement object can be observed based on the microwave frequency dependency of the inductance, the cavity resonator of the conventional electron spin resonance device having a size limitation is not required, and the device The overall size can be reduced, and the electron spin resonance apparatus can be easily taken out of the room. In addition, by making the inductor wiring spiral, it is possible to stack an insulating thin film on the spiral portion using a known CMOS (Complementary Metal Oxide Semiconductor) process, which allows it to be used in an external environment. Can also withstand. Further, the use of a permanent magnet containing ferrite as the magnetic field applying means can reduce the apparatus cost. As described above, the electron spin resonance apparatus of the present invention is advantageous in that the electron spin resonance spectrum of the measurement object can be easily observed even in an outdoor environment in addition to downsizing and weight reduction. Play.

It is a block diagram of the ESR apparatus which concerns on embodiment of this invention. It is a top view of the inductor of the ESR device concerning an embodiment of the invention. It is sectional drawing of the inductor of the ESR apparatus which concerns on embodiment of this invention. It is a figure which shows the inductance of the inductor measured in the state which does not dripping a sample to the ESR apparatus which concerns on embodiment of this invention. It is a figure which shows the inductance of the inductor measured in the state which dripped and dried the sample to the ESR apparatus which concerns on embodiment of this invention.

[Principle of the Invention]
The inventors have used a permanent magnet having a constant external magnetic field strength (magnetic flux density) instead of an electromagnet capable of adjusting the external magnetic field strength from the viewpoint of reducing the weight of the ESR device. Attention was paid to a frequency sweep method in which the ESR spectrum is observed by changing the frequency of the microwave output from the microwave transmitter in the applied state.

  When an external magnetic field is applied to the sample, energy level splitting due to the Zeeman effect occurs in the electron spin of unpaired electrons contained in the sample (that is, degeneracy is solved), and two energy levels are formed. At this time, the difference between the two energy levels is proportional to the strength (magnetic flux density) of the external magnetic field.

  When the frequency of the microwave output from the microwave transmitter is changed in the state in which these two energy levels are formed, a certain specific condition that satisfies Equation (1) corresponding to the sample that is the measurement object is obtained. In microwaves with a frequency, the energy difference between the microwave energy and the Zeeman splitting coincides. At this time, a transition occurs in the state of the unpaired electron and resonance occurs. Due to this resonance phenomenon, microwave energy is absorbed.

  In other words, even if the strength of the magnetic field is fixed, that is, even if a permanent magnet is used instead of an electromagnet, the frequency of the microwave output from the microwave transmitter is changed (frequency sweep), thereby measuring the object to be measured. In a microwave having a specific frequency satisfying the expression (1) corresponding to the sample, a behavior in which the energy of the microwave rapidly decreases is observed as an ESR spectrum.

  Also, from the viewpoint of miniaturization of the ESR device, from the conventional method in which microwaves are input to the cavity resonator through the waveguide, the inductor coil is used without using the waveguide or the cavity resonator. It was noted that the ESR spectrum may be observed as a change in inductance by placing a sample in a place corresponding to the inside, inputting and sweeping microwaves (see JP 2008-203104 A).

  Here, even in an outdoor environment, that is, in a system in which the amount of moisture such as humidity is not controlled (large dielectric loss), at least the coil portion of the inductor is required to enable observation of the ESR spectrum using the change in inductance. The surface needs to be covered with an insulating thin film. This insulating thin film also serves as a surface protection for the inductor, which is a great advantage when applied to an outdoor environment. Needless to say, the insulating thin film should be made of a material having a small dielectric loss.

  As for the coil shape of the inductor, a spiral shape capable of forming the inductor wiring on the same layer (layer) is adopted, and at least the insulating thin film is laminated thereon, thereby simplifying the manufacturing process. .

  In addition, since a microwave having a frequency of 1 GHz band (L-band) with little dielectric loss due to moisture is used, the magnetic flux density of the required magnetic field may be from several tens of mT to several tens of mT. For this reason, there is also an advantage that an inexpensive ferrite magnet may be used as a permanent magnet to be used instead of a strong neodymium magnet, samarium cobalt magnet, alnico magnet or the like. It is also possible to use a bond magnet (also called a rubber magnet, a vinyl chloride magnet, or a plastic magnet) in which ferrite magnetic powder is kneaded and molded using rubber or plastic as a binder.

[Embodiment]
Hereinafter, an ESR apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an ESR apparatus according to an embodiment of the present invention.

  The ESR device according to the present embodiment is a device that is reduced in cost in addition to being reduced in size and weight, and includes an inductor 201, a permanent magnet 202 containing ferrite, an AC voltage source function, and a frequency sweep. A measuring instrument 203 having both a function and an inductance measuring function, and an insulating thin film 204 laminated on the inductor 201 are provided. The measuring instrument 203 constitutes a current supply means, a frequency sweep means, and an inductance measurement means.

  2 is a plan view of the inductor 201, and FIG. 3 is a cross-sectional view taken along line AA of FIG. The inductor 201 includes a first wiring layer 201a made of a conductor such as aluminum or gold, and a second wiring layer 201b made of a conductor such as aluminum or gold formed below the first wiring layer 201a. Composed. The first wiring layer 201a and the second wiring layer 201b are insulated by an insulating thin film 206 as shown in FIG. The surfaces of the insulating thin film 206 and the first wiring layer 201a are covered with the insulating thin film 204.

  The starting point of the first wiring layer 201 a is connected to a surface layer pad 207 made of a conductor such as aluminum or gold formed on the insulating thin film 204 by a via 209. The starting point of the second wiring layer 201b is connected to the first wiring layer 201a by the via 210, and the end point of the second wiring layer 201b is connected to the first wiring layer 201a by the via 211. The end point of the first wiring layer 201a is connected to a surface layer pad 208 made of a conductor such as aluminum or gold formed on the insulating thin film 204 by a via 212. In this way, the inductor 201 having a spiral shape in a plan view can be manufactured by the two wiring layers 201a and 201b. The inductor 201 and the measuring instrument 203 are connected via surface layer pads 207 and 208.

It is essential for the insulating thin films 204 and 206 that the dielectric loss εr in the microwave frequency band to be used is 0.01 or less (refer to the document ““ Microwave Technology Basic Calculation ”, PUSCHNER, <http: //www.pueschner.com/basics/berechnung_en.php> ”). It goes without saying that quartz (silicon oxide) having a dielectric loss εr value of 4 × 10 ⁻⁴ is suitable as a material for the insulating thin films 204 and 206 (refer to the document “About the characteristics of quartz glass”, MARUWA, <http://www.maruwa-g.com/products/faq/images/quartz_chara.pdf> ”).

  A sample 205 as a measurement object is disposed on an insulating thin film 204 positioned inside the spiral inductor 201. Thus, when viewed from above, the sample 205 as the measurement object is in a positional relationship surrounded by the spiral inductor 201.

  A permanent magnet 202 containing ferrite as a magnetic material can apply a DC magnetic field having a magnetic flux density of, for example, tens of mT to several tens of mT to a sample 205 that is a measurement object. The permanent magnet 202 is attached and fixed to the lower surface of the insulating thin film 206 with an adhesive, for example.

  The measuring instrument 203 has a function of supplying an alternating current to the inductor 201, a function of sweeping the angular frequency of the alternating current, and a function of measuring the inductance of the inductor 201 for each angular frequency of the alternating current. Have.

  By the frequency sweep at this time, the ESR spectrum in the sample 205 as the measurement object is observed as a change in inductance. The calculation means (not shown) can calculate the g value of the sample 205 as the measurement object from the relational expression of the equation (1), and can identify the sample 205 as the measurement object from this value. At the same time, the calculation means can calculate the concentration of the sample 205 as the measurement object from the intensity of the observed ESR signal. The calculation process of the g value and concentration of the sample 205 as described above is a technique that is obvious to those skilled in the art. The calculation means can be realized by a computer having a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. The CPU executes calculation processing according to a program stored in the storage device.

  Next, the preliminary experiment result of this embodiment will be described. In this preliminary experiment, TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl) is used as the sample 205 which is a measurement object, and dielectric loss εr is used as the insulating thin films 204 and 206. Polybenzoxazole (PBO; manufactured by Sumitomo Bakelite Co., Ltd.) that is 0.01 or less was used.

  Here, the wiring width of the inductor 201 is 20 μm, the wiring interval is 10 μm, and the inner diameter of the spiral is 300 μm.

  In this preliminary experiment, a microsyringe (for example, a capillary syringe having a needle outer diameter of 200 μm, manufactured by Ito Manufacturing Co., Ltd.) is used on the insulating thin film 204 positioned inside the spiral inductor 201. 1 μl of TEMPOL solution (solvent is isopropyl alcohol) was dropped and dried to place the sample 205 as a measurement object.

  A magnet containing a ferrite with a magnetic flux density of 10.8 mT (for example, a magnet sheet manufactured by KOKUYO S & T Co., Ltd., model number Mac-S340) is used as the permanent magnet 202 and is output from the measuring instrument 203 in a range of about 10 MHz to 10 GHz. The angular frequency of the alternating current was swept. As the measuring instrument 203, N5230A 10MHz-40GHz PNA-L Network Analyzer (manufactured by Agilent Technologies) was used.

  4 and 5 are diagrams showing the inductance of the inductor 201 measured by the measuring instrument 203. FIG. 4 and 5, the horizontal axis represents angular frequency, and the vertical axis represents inductance.

  FIG. 4 is a diagram showing the inductance of the inductor 201 measured without dropping the above TEMPOL solution (sample 205). Since the sample 205 was not dripped, the characteristic change derived from ESR was not observed.

FIG. 5 is a diagram showing the inductance of the inductor 201 measured after 1 μl of the TEMPOL solution (sample 205) is dropped on the insulating thin film 204 located inside the spiral inductor 201 and dried. . A characteristic change derived from ESR was observed around 48.4 MHz. That is, the resonance angular frequency ω ₀ was detected as 48.4 MHz.

By converting this resonance angular frequency ω ₀ to the resonance frequency ν ₀ and substituting it into the equation (1), the g value is obtained as 2.0058. From this g value, it is identified that the sample 205 which is a measurement object is TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl).

  As described above, in the present embodiment, since the ESR spectrum of the measurement object can be observed based on the microwave frequency dependence of the inductance of the inductor 201, the cavity resonator of the conventional ESR device having a size limit is provided. It becomes unnecessary, and it is possible to reduce the size of the entire apparatus. Further, there is an advantage that the angular frequency of the alternating current can be freely set without being restricted by the cavity resonator.

  Furthermore, in the present embodiment, the intensity (magnetic flux density) of the external magnetic field applied to the sample 205 as the measurement object is closely related to the angular frequency (frequency), but the angle of the alternating current supplied to the inductor 201 is Since the frequency can be freely set, for example, a permanent magnet 202 containing lightweight ferrite can be used as a magnetic field applying means suitable for taking out to the outdoors.

  The electron spin resonance apparatus of the present invention achieves an effect that an electron spin resonance spectrum can be easily observed even in an outdoor environment by reducing the size, weight, and cost. It is useful for environmental evaluation such as measurement, water purification, malodor decomposition, decomposition of harmful substances in exhaust gas, removal of soil pollutants, and dioxin decomposition.

  DESCRIPTION OF SYMBOLS 201 ... Inductor, 201a, 201b ... Wiring layer, 202 ... Permanent magnet, 203 ... Measuring instrument, 204, 206 ... Insulating thin film, 205 ... Sample, 207, 208 ... Surface layer pad, 209-212 ... Via.

Claims (3)

In an electron spin resonance apparatus that observes an electron spin resonance spectrum of a measurement object,
Magnetic field applying means for applying a magnetic field to the measurement object;
A spiral inductor arranged so as to surround the measurement object;
Current supply means for supplying an alternating current to the inductor;
Frequency sweeping means for sweeping the angular frequency of the alternating current;
Inductance measuring means for measuring the inductance of the inductor for each angular frequency swept by the frequency sweep means,
The inductor is covered with an insulating thin film having a dielectric loss of 0.01 or less,
The electron spin resonance apparatus, wherein the sample is disposed on the insulating thin film positioned inside the spiral inductor. The electron spin resonance apparatus according to claim 1.
The electron spin resonance apparatus, wherein the magnetic field applying means is a permanent magnet containing ferrite as a magnetic material. The electron spin resonance apparatus according to claim 1 or 2,
The electron spin resonance apparatus further comprises calculation means for calculating a g value which is an electron spin resonance parameter based on a resonance angular frequency observed from a change in inductance measured by the inductance measurement means.

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