CN104062269A - Nanosecond time-resolved absorption and emission spectrum measuring device and measuring method - Google Patents

Abstract

The invention relates to a nanosecond time-resolved absorption and emission spectrum measurement device. The excitation light source is sequentially connected with a first sequence pulse generator, a working frequency coordinator, a second sequence pulse generator, and a data collector; the second sequence pulse is generated The detectors are respectively connected with the optical path system and the detection light source; the data collectors are respectively connected with the working frequency coordinator, the first light intensity detector, the second light intensity detector, the third light intensity detector, and the monochromator; the detection light source is connected with the monochromator An optical path system and a sample pool are also arranged between the colorimeters. The measurement method is to set the sample temperature, the excitation light source emits a light beam to irradiate the sample to the electronically excited state, and obtains the zero moment of the time-resolved spectral data through part of the light beam; the detection light intensity signal after the pulsed white light emitted by the detection light source passes through the sample is fed back to data logger and convert to absorption and emission spectra. The invention is equipped with a temperature-adjustable sample pool, and can obtain spectral data with a high signal-to-noise ratio.

Description

Nanosecond time-resolved absorption and emission spectroscopy measurement device and measurement method

technical field

The invention relates to a time-resolved spectrum measuring device and method, in particular to an instrument and method capable of measuring nanosecond time-resolved absorption and emission spectra respectively under the condition that the sample temperature can be adjusted.

Background technique

The photosynthesis of plants and the photodegradation of pollutants provide human beings with a source of food and a good living environment. Studying the physical and chemical processes triggered by light helps to understand these natural phenomena. New technical ideas. In general, the light-triggered chemical reaction path is: when a substance in the electronic ground state is irradiated by a light beam of a suitable wavelength, the electrons of the substance are triggered to an excited state, forming intermediates with strong reactivity, and generating electrons in different environments The final product in the ground state (Document 1: Fan Meigong, Yao Jiannian, Tong Zhenhe, etc., Molecular Photochemistry and Optical Functional Materials Science, Beijing: Science Press, 2009). The characteristics of excited state substances will greatly affect the path of photochemical reactions, especially the long-lived excited state substances have more important research value. Such long-lived excited state substances have sufficient time to make their own active electrons To exert its functionality, the lifetime of this excited state substance is often in the time scale of nanoseconds to milliseconds (document 2: HXHan, MNPaddon-row and RFHowe, Charge separation in mesoporous aluminosilicates, Res. Chem. Intermed., 2008, 34, 551 -564; JWVerhoeven, HJvan Ramesdonk and MMGroeneveld, et al.Long-livedcharge-transfer states in compact donor-acceptor dyads, ChemPhysChem ,2005,6,2251-2260), detecting the characteristics of excited state substances has become a difficult problem that people need to break through , time-resolved spectral testing technology has become a powerful means to solve the problem.

Mature commercial spectroscopic testing devices are mainly concentrated in steady-state absorption and emission spectrometers. The two most representative companies that produce this type of product are PerkinElmer of the United States (Document 3: http://www.perkinelmer.com/) and French company Horiba Jobin Yvon (Document 4: http://www.horiba.com/cn/), spectroscopic equipment with time-resolving functions often has a single function, specifically, an existing set of equipment can only measure time Resolved absorption spectrum or time-resolved emission spectrum, the longest measurement time scale is on the order of microseconds, the sample temperature can only be approximately equal to room temperature, and cannot be adjusted. The two most representative companies that produce this type of product They are British Edinburgh Instruments Ltd (Document 5: http://www.edinst.com/) and British Applied Photophysics Company (Document 6: http://www.photophysics.com/).

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a kind of experimental device and method for measuring nanosecond time-resolved absorption and emission spectra, and the technical scheme adopted by the present invention for realizing the above-mentioned purpose is:

The nanosecond time-resolved absorption and emission spectrum measurement device, the excitation light source is sequentially connected with the first sequence pulse generator, the working frequency coordinator, the second sequence pulse generator, and the data collector; the second sequence pulse generator is respectively connected with the optical path system , the detection light source connection; the data collector is respectively connected with the working frequency coordinator, the first light intensity detector, the second light intensity detector, the third light intensity detector, and the monochromator; the detection light source and the monochromator are also connected Equipped with optical path system and sample pool.

The light-emitting port of the detection light source is in a straight line with the sample in the sample cell and the position of the entrance of the monochromator.

The light beam emitted by the exciting light source is perpendicular to the pulsed light beam emitted by the detection light source.

The sample pool includes: the outer surface of the cavity bottom of the built-in cuvette is sequentially pasted with a semiconductor refrigerator and a temperature-controlling metal block, and a liquid circulation path is built inside the temperature-controlling metal block, and the liquid in the low-temperature constant temperature tank drives the liquid through a circulating pump To the circulation path; a temperature sensor is installed on the inner wall of the chamber.

A nanosecond time-resolved method for measuring absorption and emission spectroscopy, comprising the steps of:

(1) Setting the detection wavelength of the monochromator;

(2) The first sequence of pulse generators (send two identical frequency signals I and II to trigger the excitation light source and the working frequency coordinator to work respectively, and the working frequency coordinator sends out frequency signal III to trigger the second sequence of pulse generators, and the second sequence The pulse generator sends out three frequency signals IV, V, VI to trigger the optical system, detection light source, and data collector respectively;

(3) The excitation light source emits a nanosecond pulse beam to irradiate the sample in the sample cell to the electronically excited state, and part of the beam is reflected to the second light intensity detector through the optical path system, and the second light intensity detector sends a pulse signal to the data collector as The zero moment of time-resolved spectral data; after the pulsed white light emitted by the detection light source passes through the sample, it is recorded by the light intensity detector after passing through the monochromator, and the detected light intensity signal is fed back to the data collector;

(4) Repeat steps (2) to (4) to average the detection light intensity signals collected by the data collector multiple times;

(5) Reset the detection wavelength of the monochromator and repeat steps (2) to (4), and convert the average value of the detection light intensity signals collected by the data collector at different detection wavelengths into absorption and emission spectra.

The frequency signal I is delayed relative to the frequency signal II.

The frequency signal V is delayed relative to the frequency signal III.

The frequency signal VI is delayed relative to the frequency signal III.

The frequency signal IV is synchronized with the frequency signal III.

The present invention has the following beneficial effects and advantages:

1. The present invention is equipped with a temperature-adjustable sample cell and a set of equipment with two measurement modes for transient absorption and emission spectra.

2. The function of setting the average number of measurements according to requirements in the device and measurement method of the present invention helps to obtain spectral data with a high signal-to-noise ratio.

Description of drawings

Fig. 1 is a schematic diagram of the structure principle of the present invention;

Fig. 2 is the measured transient absorption and emission spectrogram of the embodiment of the present invention;

Fig. 3 is a schematic view of the sample cell structure of the present invention;

Among them: 1 excitation light source, 2 detection light source, 3 monochromator or polychromator, 4-1 first light intensity detector, 4-2 second light intensity detector, 4-3 third light intensity detector, 5 data Collector, 5-1 data acquisition card, 5-2 computer, 5-3 oscilloscope, 6 sample pool, 7-1 shutter controller, 7-2 shutter, 7-3 mirror, 7-4 focusing mirror, 8- 1 first sequence pulse generator, 8-2 second sequence pulse generator, 9 working frequency coordinator, 10 cavity, 11 semiconductor refrigerator, 12 temperature control metal block, 13 liquid circulation path, 14 low temperature constant temperature bath, 15 Circulation pump, 16 temperature sensors, 17 temperature control tables.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

In the sample cell of the present invention, the sample is controllably set at a temperature within the range of -50°C-50°C, and the time-resolved absorption and emission spectra of the excited state of the sample are measured within the range of wavelength 200nm-900nm and time 50ns-2ms , the minimum intensity resolution is about 0.0005, and the measurement frequency is adjustable in the range of 1Hz-5Hz. In order to obtain a high signal-to-noise ratio, the present invention obtains the final experimental result by taking the average of multiple measurements, and the average times are adjustable. The device will provide reliable technical support for developing clean energy regeneration technology and exploring new solutions for environmental protection.

The present invention completed according to the above-mentioned purpose is to complete the measurement work mode as follows: first set the sample temperature, the excitation light source excites the sample to a certain electronic excited state, and when the detection light source is in the working state, the pulse it sends is strengthened White light passes through the excited state material, and the transmitted white light is measured by the light intensity detector, and then the data acquisition system records and converts the light intensity into transient absorption spectrum data. When the detection light source is turned off, the sample in the electronically excited state emits light It is directly measured by the light intensity detector, and then the data acquisition system records and converts the light intensity into transient emission spectrum data. The working time sequence of the above-mentioned parts is coordinated by the sequence pulse generator and the working frequency coordinator.

As shown in Figure 3, the temperature-controllable sample cell of the present invention can controllably set the test sample to a certain temperature between -50°C and 50°C, and its composition method is: made of copper or aluminum A cavity 10 for placing a cubic quartz cuvette, the cavity has round holes 18 on three sides to transmit light, and the bottom surface is smooth, and the cooling surface of the semiconductor refrigerator 11 is tightly pasted on the lower surface of the cavity 10 with heat-conducting adhesive The other side of the semiconductor refrigerator 11 is closely connected with the temperature-controlling metal block 12 with heat-conducting adhesive. The temperature-controlling metal block 12 is a hollow metal block with an inlet for inflowing liquid and an outlet for outflowing liquid. The outlet, the inlet and the outlet are connected to the low-temperature constant temperature tank 14 through water pipes to form a liquid circulation path; the liquid in the low-temperature constant temperature tank 14 is driven by a circulating pump 15, so that the temperature-controllable liquid is constantly flowing in the temperature-controlling metal block 12 Flow in the liquid circulation path, the temperature of the controllable metal block 12 is equal to the liquid temperature in the low temperature tank 14, when the semiconductor refrigerator is supplied with positive voltage, the sample temperature in the quartz cuvette will drop, when the semiconductor refrigerator is supplied with negative voltage , the temperature of the sample in the quartz cuvette will rise, the probe of the temperature sensor 16 is placed deep inside the cavity, and the temperature control meter 17 is connected externally; when the measured temperature reaches the set temperature, the sensor sends an instruction to stop power supply, when the measured temperature deviates When setting the temperature, the temperature control table 17 sends instructions to supply power to the semiconductor refrigerator to achieve the purpose of regulating temperature. By reasonably setting the magnitude of the supply voltage and the temperature of the liquid in the cryostat, the sample cell 6 can controllably set the sample temperature between -50°C and 50°C.

The function of the working frequency coordinator 9 in the present invention is to make the exciting light source 1 working at a high repetition rate and the detection light source 2 working at a low repetition rate work together. Normally, the excitation light source 1 needs to obtain a stable working mode at a higher repetition frequency, while the detection light source 2 needs to obtain a stable working mode at a lower repetition frequency, and the working frequency coordinator 9 will excite the light source The high repetition frequency trigger signal of 1 is reduced to a suitable low frequency signal, which is used as the external trigger signal of the detection light source 2, so that the excitation light source 1 and the detection light source 2 can work synchronously and harmoniously.

The integrated electronic chip model and connection method used by the working frequency coordinator 9 are as follows: the trigger signal with a high repetition rate first passes through the inverter I (chip model 7404), then passes through the counter (chip model CD4040), and then passes through the NAND gate ( Chip model CD4011), then through the inverter II (chip model 7404), then through the NAND gate (chip model 7400), and then through 2 monostable flip-flops (chip model 74123) output with a certain delay phase and pulse width The negative pulse, and finally through the power amplifier (chip model 74128) to output the final external trigger signal with adjustable low repetition frequency width, where the other input terminal of the NAND gate (chip model 7400) mentioned above is connected to the data acquisition card 5 -1 output port, when the computer 5-2 sent a high-level command by the data acquisition card 5-1, the NAND gate was in an open state, and when the computer 5-2 sent a low-power command by the data acquisition card 5-1 When the command is equal, the NAND gate is in the closed state, so that the computer-controlled switching function of this device can be realized. In addition, the output of the inverter II (chip model 7404) mentioned above is connected to two series-connected Monostable flip-flop (chip model 74123), whose output signal is sent to the clear function pin of the counter mentioned above (chip model CD4040).

The optical path system 7 is used to control the beam diameter and propagation direction, and can use optical reflection, focusing elements and mechanical shutters. In this embodiment, a shutter controller 7-1, two shutters 7-2, and a mirror 7-3 are included. , a focusing mirror 7-4. Among them, a shutter 7-2, a reflection mirror 7-3 and a focusing mirror 7-4 are sequentially placed between the excitation light source and the sample, and the shutter is used to block redundant excitation light pulses; the other shutter 7-2 is placed Between the detection light source and the sample, it is used to block excess detection light irradiation.

The data collector 5 includes a data acquisition card 5-1, a computer 5-2 and an oscilloscope 5-3. The data acquisition card 5-1 is used to collect the data sent by the pulse signal generator 8, and is connected with the working frequency coordinator 9, the second sequence pulse generator 8, the light intensity detector 4-1, and the computer 5-2; the computer 5 -2 is used to collect the light intensity data in the oscilloscope 5-3, and convert the light intensity data into transient absorption spectrum data; the computer 5-2 is connected with the monochromator 3 and the oscilloscope 5-3; the oscilloscope 5-3 is used for Read light intensity data, and connect with light intensity detectors 4-2, 4-3.

Figure 1 shows the technical roadmap of the present invention. The experimental sample is 3mL of 4mM benzil acetonitrile solution. First, the temperature of the liquid is set at 22°C by the temperature-controllable sample pool 6, and the computer 5-2 specifies that the measurement wavelength range of the monochromator 3 is 350nm by instruction. The characteristic of the pulse emitted by the excitation light source 1 is 33mJ355nm. As shown in Figure 1, firstly, two trigger signals with a repetition frequency of 10Hz are issued by the sequence pulse generator 8-1 (DG535 of SRS Company of the United States), which are respectively I and II, in which the signal I is delayed by 9ms from II, and II is used as the input signal Delivered to the working frequency coordinator 9, the computer control data acquisition card 5-1 in the data collector 5 sent the high-level signal VII to open the working frequency coordinator 9, after reducing the frequency effect, the working frequency coordinator 9 Send out a low repetition frequency 3Hz signal III synchronous with II, this signal is passed as an external trigger signal to the second sequence pulse generator 8-2 (SRS company DG645 in the United States), which sends out three 3Hz signals IV, V, VI, Among them, IV and III are synchronized in time, and the two mechanical shutters 7-2 are in the open state after receiving IV. The opening duration is 12ms, and V is delayed by 7.3ms from III. After receiving V, the detection light source 2 sends out a pulse with a width of 6ms. The enhanced white light pulse, VI is 13ms later than III, and the data acquisition card 5-1 starts to record data after receiving this signal VI. After the excitation light source 1 receives I, it emits a nanosecond pulsed beam with a wavelength of 355 nm to irradiate the sample to an electronically excited state. At this time, the pulsed white light emitted by the detection light source 2 just passes through the electronically excited state sample perpendicular to the direction of the excitation light. After the transmitted light passes through the monochromator 3, it is recorded by the light intensity detector 4-3, and the intensity signal is transmitted to the oscilloscope 5-3 in the data collector 5, and a very small part of the excitation pulse light is reflected to the left in Fig. 1 When the light intensity detector 4-2 on the side (photodiode with nanosecond turn-on time) sends a pulse signal to the oscilloscope 5-3 as the zero moment of the time-resolved spectral data, then the data acquisition card 5-1 receives the After the VI, store the data in the oscilloscope 5-3 to complete a measurement process. Continuously measure 100 times at the 350nm position of the monochromator 3, and take the average result as the final test result, and then the computer sets the detection of the monochromator 3. The wavelength is 355nm, measure again at this position 100 times, and store the average result, and so on, until the detection wavelength of the monochromator 3 is 650nm, and after completing 100 measurements and taking the average result, the entire experiment process ends, and the experimental data is stored in the computer.

Figure 2 shows the experimental results obtained in the above experimental process. This figure is the transient absorption and emission spectra obtained by 4mM benzil acetonitrile solution under the excitation condition of 33mJ355nm. Since the single wavelength result is obtained by the average of 100 measurement results, Therefore, the signal-to-noise ratio of the data is high, which contains rich physical and chemical connotations, and has great scientific research value. Figure 3 shows a pictorial view of the temperature-controlled sample cell in the device of the present invention, which is robust and works well with other components of the present invention.

Claims (9)

1. Nanosecond time-resolved Absorption and emission spectra measurement mechanism, it is characterized in that: excitation source (1) and First ray pulse producer (8-1), frequency of operation telegon (9), the second train pulse generator (8-2), data acquisition unit (5) are linked in sequence; The second train pulse generator (8-2) is connected with light path system (7), probe source (2) respectively; Data acquisition unit (5) is connected with frequency of operation telegon (9), the first light intensity detector (4-1), the second light intensity detector (4-2), the 3rd light intensity detector (4-3), monochromator (3) respectively; Between probe source (2) and monochromator (3), be also equipped with light path system (7) and sample cell (6).
2. Nanosecond according to claim 1 time-resolved Absorption and emission spectra measurement mechanism, it is characterized in that: sample, monochromator (3) position, entrance port in the light outlets of described probe source (2) and sample cell (6) are a straight line.
3. Nanosecond according to claim 1 time-resolved Absorption and emission spectra measurement mechanism, it is characterized in that: the pulsed light beam of the light beam that described excitation source (1) sends and probe source (2) transmitting is vertical.
4. Nanosecond according to claim 1 time-resolved Absorption and emission spectra measurement mechanism, it is characterized in that: described sample cell (6) comprising: cavity (10) bottom outer surface of built-in cuvette posts semiconductor cooler (11), temperature control derby (12) successively, temperature control derby (12) inside is equipped with liquid-circulating path (13), and the liquid in low temperature thermostat bath (14) drives liquid in circulation path (13) through ebullator (15); Cavity (10) inwall is equipped with temperature sensor (16).
5. Nanosecond time-resolved Absorption and emission spectra measuring method, it is characterized in that comprising the following steps:

   (1) the detection wavelength of setting monochromator (3);

   (2) First ray pulse producer (8-1) sends frequency signal I, the II that two-way is identical and triggers respectively excitation source (1) and frequency of operation telegon (9) work, frequency of operation telegon (9) sends frequency signal III and triggers the second train pulse generator (8-2), and the second train pulse generator (8-2) sends three road frequency signal IV, V, VI trigger respectively light path system (7), probe source (2), data acquisition unit (5);

   (3) sample that excitation source (1) sends in nanosecond pulse light beam irradiates sample cell (6) arrives excited electronic state, its segment beam is reflected to the second light intensity detector (4-2) through light path system (7), the second light intensity detector (4-2) send pulse signal to data acquisition unit (5) moment at zero point as time resolved spectroscopy data; The pulse white light that probe source (2) sends is through after sample, and after monochromator (3), by light intensity detector (4-3) record, this detection light intensity signal feeds back to data acquisition unit (5);

   (4) repeating step (two)～(four), average the detection light intensity signal of data acquisition unit (5) multi collect;

   (5) reset the detection wavelength of monochromator (3) and repeat step (two)～(four), detection light intensity signal mean value when data acquisition unit (5) is gathered to different detection wavelength converts Absorption and emission spectra to.
6. Nanosecond according to claim 5 time-resolved Absorption and emission spectra measuring method, it is characterized in that: described frequency signal I has time delay with respect to frequency signal II.
7. Nanosecond according to claim 5 time-resolved Absorption and emission spectra measuring method, it is characterized in that: described frequency signal V has time delay with respect to frequency signal III.
8. Nanosecond according to claim 5 time-resolved Absorption and emission spectra measuring method, it is characterized in that: described frequency signal VI has time delay with respect to frequency signal III.
9. Nanosecond according to claim 5 time-resolved Absorption and emission spectra measuring method, it is characterized in that: described frequency signal IV is synchronizeed with frequency signal III.