A single silicon nanowire fluorescent ratiometric thermometer and its preparation method and application

Abstract

The application discloses a single silicon nanowire fluorescent ratio type thermometer and a preparation method and application thereof. The single silicon nanowire fluorescent ratio type thermometer takes a single silicon nanowire as a substrate, and the surface of the single silicon nanowire is decorated with temperature-sensitive up-conversion nanoparticles; the up-conversion nanoparticles are NaYF4(Yb, Er). The single silicon nanowire fluorescent ratio type thermometer can effectively avoid the space drift problem of a traditional zero-dimensional nanoparticle thermometer when detecting the temperature of a micro space, and thus the spatial resolution can be improved. Meanwhile, the single silicon nanowire fluorescent ratio type thermometer uses the fluorescence ratio of the up-conversion nanoparticles as a detection index, can eliminate the interference of probe concentration fluctuation on a signal, and improves the detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of nanothermometers. More specifically, it relates to a single silicon nanowire fluorescence ratio thermometer, its preparation method, and its application. Background Technology

[0002] Cellular temperature is related to many chemical reactions, such as enzymatic reactions, gene expression, and protein synthesis. Different types of cells, and even different cells of the same type, exhibit individual temperature variations due to differences in the reactions they undergo and their physiological environments. Furthermore, temperatures also differ at different spatial locations within the same cell; areas experiencing vigorous biochemical reactions are generally warmer, while areas with milder reactions are typically cooler. Therefore, precisely studying the temperature at different locations within a cell not only helps in understanding cellular physiological activities and revealing the pathogenesis of diseases at the cellular level, thus promoting disease diagnosis and drug development, but also contributes to a better understanding of intercellular differences and the study of physiological processes such as cellular metabolism and intercellular signal transduction.

[0003] Real-time visualization and monitoring of temperature is a primary method for studying temperature at different locations within cells. Fluorescence sensing, a semi-invasive thermometry method with advantages such as high sensitivity, rapid response, and visualization, has been widely applied in fields such as biomedicine. However, currently widely studied fluorescent nanothermometers primarily use nanoparticles as substrates, and fluorescent probes are mostly based on downconversion fluorescent emitting substances. During testing, these fluorescent nanothermometers are prone to spatial drift of the substrate, reducing the spatial resolution of the measurement. Furthermore, fluorescent probes based on downconversion fluorescence emission have poor penetration into biological tissues and can cause some damage. They are also susceptible to interference from the autofluorescence of biological tissues and fluctuations in the concentration of fluorescent substances in the probes, leading to measurement errors.

[0004] Therefore, there is a need for a single silicon nanowire fluorescence ratio thermometer that is unaffected by the external environment, avoids interference from fluorescent probe concentration, and has high spatial resolution to accurately detect the temperature in minute spatial locations. Summary of the Invention

[0005] The first objective of this invention is to provide a single-strand silicon nanowire fluorescence ratio thermometer. This thermometer can effectively avoid interference with test results caused by environmental factors and fluctuations in the concentration of fluorescent substances.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned single silicon nanowire fluorescent ratio thermometer.

[0007] A third objective of this invention is to provide the application of the above-described single silicon nanowire fluorescent ratio thermometer in temperature measurement within micrometer-scale micro-spaces.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a single silicon nanowire fluorescence ratio thermometer, wherein the single silicon nanowire fluorescence ratio thermometer uses a single silicon nanowire as a substrate, and the surface of the single silicon nanowire is modified with temperature-sensitive upconversion nanoparticles; the upconversion nanoparticles are NaYF4(Yb,Er).

[0010] The thermometer of this invention uses a single silicon nanowire as a substrate. This one-dimensional nanowire can be inserted into specific micro-systems, such as specific parts of a cell, via micromanipulation, thereby achieving high spatial resolution temperature detection of these micro-systems. Secondly, the thermometer of this invention uses upconversion nanoparticles as temperature-sensitive probes. These upconversion nanoparticles contain multiple fluorescence emission peaks, and the ratio of these peaks changes with temperature. Therefore, the fluorescence ratio thermometer of this invention can eliminate interference from downconversion fluorescence signals and avoid measurement errors caused by fluctuations in the concentration of the temperature-sensitive probe.

[0011] Furthermore, in the NaYF4(Yb,Er), the molar content of Yb is 10-30%, and the molar content of Er is 1-5%. This specific composition of NaYF4(Yb,Er) exhibits superior temperature sensitivity.

[0012] Furthermore, the length of the single silicon nanowire is 100μm-150μm and the diameter is 150nm-200nm.

[0013] Furthermore, the NaYF4(Yb,Er) can be prepared by the following method, specifically including the following steps:

[0014] YCl3·6H2O, YbCl3·6H2O, and ErCl3·6H2O were dispersed in a mixed solution of oleic acid and octadecene, and thoroughly sonicated. Under vacuum, the temperature was raised to 120℃-130℃ and maintained for 5-10 minutes. The temperature was then allowed to cool naturally to 30℃-40℃. NH4F and NaOH were added, and the mixture was heated to 250℃-350℃ under nitrogen atmosphere for 1-2 hours. The mixture was then washed.

[0015] Among them, the above preparation method produces NaYF4(Yb,Er) with uniform morphology and higher luminescence efficiency.

[0016] For example, the volume of oleic acid is 6 mL to 10 mL, and the volume of octadecene is 10 mL to 20 mL.

[0017] Furthermore, the cleaning includes a primary cleaning and a secondary cleaning. The primary cleaning is performed using a mixture of cyclohexane and ethanol. The secondary cleaning is performed using a mixture of ethanol and water. In the secondary cleaning, the pH of the mixture is 0-3. The purpose of the secondary cleaning is to remove oleic acid from the surface of NaYF4(Yb,Er).

[0018] Preferably, the volume ratio of cyclohexane to ethanol is 1:1;

[0019] Preferably, the volume ratio of ethanol to water is 0.5-2:0.5-2.

[0020] Secondly, the present invention provides a method for preparing a single silicon nanowire fluorescence ratio thermometer, the method comprising the following steps:

[0021] Step 1: The silicon nanowire array is sequentially subjected to hydroxylation and carboxylation treatments, and after exfoliation, a single silicon nanowire with a carboxylated surface is obtained;

[0022] Step 2: Prepare an aqueous dispersion of the surface-carboxylated monosilicon nanowires, add the upconversion nanoparticles, adjust the pH to 9-14 using ammonia, add tetraethyl orthosilicate (TEOS), shake to react, and wash thoroughly with deionized water.

[0023] Hydroxylation and carboxylation treatments can enhance the hydrophilicity of silicon nanowire arrays, making them easier to modify. TEOS hydrolyzes and condenses into SiO2 under alkaline conditions. SiO2 coats NaYF4(Yb,Er) onto the surface of the entire single silicon nanowire. The thermometer prepared by the method provided by this invention has better temperature sensitivity.

[0024] Furthermore, the conditions for the oscillation reaction are: an oscillation rate of 500 r / min-1500 r / min and an oscillation time of 1 h-12 h. These reaction conditions allow NaYF4(Yb,Er) to be more uniformly coated on the surface of the single silicon nanowire.

[0025] For example, in step two, the upconversion nanoparticles may be added in excess.

[0026] For example, the silicon nanowire array can be fabricated using Ag. + The auxiliary chemical etching method specifically includes the following steps: first, immersing the silicon wafer in a mixed solution of silver nitrate, hydrofluoric acid and water to deposit a layer of silver particles on the silicon wafer; then etching the obtained silicon nanowire array in a mixed solution of hydrofluoric acid, hydrogen peroxide and water.

[0027] For example, the etching temperature is 40℃-60℃ and the etching time is 100min-150min.

[0028] For example, the soaking time is 8-10 minutes.

[0029] Furthermore, the hydroxylation treatment includes the following steps: immersing the silicon nanowire array in a mixed solution of concentrated sulfuric acid and hydrogen peroxide, heating and refluxing, cleaning it, then immersing it in a mixed solution of H2O, 30% H2O2 and NH3·H2O, cleaning it, and then drying it.

[0030] For example, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3-5:1, and the concentrated sulfuric acid has a concentration of 18.4 mol / L.

[0031] For example, the volume ratio of H2O, 30% H2O2 and NH3·H2O is 5:1:1.

[0032] For example, the heating reflux time is 1h-2h.

[0033] For example, the soaking time is 3h-10h.

[0034] Furthermore, the carboxylation treatment includes the following steps: adding deionized water to the hydroxylated silicon nanowire array, adding sodium carboxyethylsilane triol, shaking the reaction thoroughly, and then cleaning with deionized water.

[0035] For example, the amount of deionized water added is 5 mL to 10 mL.

[0036] For example, the volume of the sodium carboxyethylsilane triol is 100 μL-400 μL.

[0037] For example, the oscillation rate is 500 r / min-1500 r / min, and the oscillation time is 1 h-12 h.

[0038] Thirdly, the present invention provides an application of the above-mentioned single silicon nanowire fluorescent ratio thermometer in temperature measurement within a micrometer-scale space.

[0039] Furthermore, the micron-scale tiny space includes the space within a single cell.

[0040] Furthermore, the application includes the following steps:

[0041] At least one end of the aforementioned single silicon nanowire fluorescence ratio thermometer is inserted into the measurement location in a micrometer-scale space. A laser scanning confocal microscope (LSCM) is used to perform fluorescence imaging on the silicon nanowire fluorescence ratio thermometer, and the fluorescence intensity ratio (FIR) at wavelengths of 525 nm and 545 nm is obtained. The temperature at the measurement location is calculated using a standard curve. The laser excitation wavelength of the laser scanning confocal microscope is 980 nm.

[0042] Furthermore, the plotting of the standard curve includes the following steps:

[0043] 1) The fluorescence intensity ratio of the single silicon nanowire fluorescence ratio thermometer at different test temperatures was tested using a laser scanning confocal microscope at wavelengths of 525 nm and 545 nm, wherein the laser excitation wavelength of the laser scanning confocal microscope was 980 nm.

[0044] 2) A standard curve was obtained by fitting the test temperature as the x-axis and the ratio of fluorescence intensity at wavelengths of 525 nm and 545 nm (FIR) as the y-axis.

[0045] For example, the single silicon nanowire fluorescence ratio thermometer of the present invention can be inserted into a single cell through cell incubation or micromanipulation techniques, and then excited by a 980nm laser configured on an LSCM to collect fluorescence intensity in the 490nm-620nm range for fluorescence spectral imaging. By measuring the FIR values ​​of the silicon nanowire fluorescence ratio thermometer at different spatial locations, the temperature at different spatial locations can be obtained.

[0046] The beneficial effects of this invention are as follows:

[0047] (1) The single silicon nanowire fluorescence ratio thermometer of the present invention uses the ratio of the fluorescence intensities of two points of NaYF4(Yb,Er) itself as the monitoring index when performing temperature detection, which can effectively reduce the influence of probe concentration fluctuation on the signal. At the same time, the excitation wavelength is 980nm and the monitoring window is 490nm-620nm, which can effectively avoid downconversion autofluorescence interference.

[0048] (2) The single silicon nanowire fluorescence ratio thermometer of the present invention can realize temperature detection at different spatial locations in a small area with the help of a micro-manipulation platform. In addition, the thermometer has strong resistance to photobleaching and excellent anti-interference ability, making it suitable for detection in complex environments.

[0049] (3) The single-silicon nanowire fluorescence ratio thermometer of the present invention uses a single silicon nanowire as a substrate. This substrate has good biocompatibility, and the nanometer-scale diameter causes little damage to cells. The micrometer-scale length can greatly reduce the Brownian motion of the substrate, avoiding the spatial drift of traditional zero-dimensional nanoparticles during the testing process, and improving the spatial resolution during detection.

[0050] (4) The preparation method of the single silicon nanowire fluorescent ratio thermometer of the present invention is simple and can be mass-produced. Attached Figure Description

[0051] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0052] Figure 1 A schematic diagram illustrating the fabrication principle of the fluorescent ratio thermometer based on a single silicon nanowire in Example 1 is shown.

[0053] Figure 2 A scanning electron microscope image of the silicon nanowire array of Example 1 is shown;

[0054] Figure 3 This shows a transmission electron microscope (TEM) image of a single silicon nanowire from Example 1.

[0055] Figure 4 The transmission electron microscope image of NaYF4(Yb,Er) from Example 1 is shown.

[0056] Figure 5 The X-ray diffraction energy spectrum of NaYF4(Yb,Er) in Example 1 is shown.

[0057] Figure 6 The fluorescence spectrum of NaYF4(Yb,Er) from Example 1 is shown.

[0058] Figure 7 The FIR curve of NaYF4(Yb,Er) in Example 1 as a function of temperature is shown.

[0059] Figure 8 The FIR temperature resolution plots of NaYF4(Yb,Er) from Example 1 at different temperatures are shown.

[0060] Figure 9 The relative sensitivity of the FIR curve of NaYF4(Yb,Er) as a function of temperature is shown in Example 1.

[0061] Figure 10 The FIR of NaYF4(Yb,Er) in Example 1, tested under different interfering ions, is shown.

[0062] Figure 11The images show fluorescence spectral imaging and bright-field imaging of a single silicon nanowire under 980 nm laser irradiation, as shown in Example 1; wherein, a shows the fluorescence spectral imaging of a single silicon nanowire under 980 nm laser irradiation, and b shows the bright-field imaging of a single silicon nanowire under 980 nm laser irradiation.

[0063] Figure 12 A fluorescence image of the single silicon nanowire fluorescence ratio thermometer of Example 1 is shown.

[0064] Figure 13 The fluorescence spectrum of the single silicon nanowire fluorescent ratio thermometer of Example 1 is shown.

[0065] Figure 14 The graph shows the FIR variation with temperature for the single silicon nanowire fluorescent ratio thermometer of Example 1.

[0066] Figure 15 The fluorescence image of the single silicon nanowire fluorescence ratio thermometer of Comparative Example 1 is shown.

[0067] Figure 16 The following are fluorescence images of the modified NaYF4(Yb,Er) silicon nanowire array and the single silicon nanowire fluorescence ratio thermometer of Comparative Example 2; wherein, a shows the fluorescence intensity map of the modified NaYF4(Yb,Er) silicon nanowire array; b shows the fluorescence intensity map of the single silicon nanowire fluorescence ratio thermometer. Detailed Implementation

[0068] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] Step 1: Fabrication of silicon nanowire arrays

[0071] A 1×1 cm n-type silicon wafer was cut and ultrasonically cleaned for 5 min each with acetone, ethanol, and deionized water. The wafer, face up, was immersed in a mixed solution of 0.153 g silver nitrate, 40 mL hydrofluoric acid, and 140 mL deionized water for 8 min. After removal, the wafer was cleaned and then added to a mixed solution of 40 mL hydrofluoric acid, 4 mL hydrogen peroxide, and 136 mL deionized water. Etching was performed at 50°C for 120 min. The etched wafer was then immersed in aqua regia for 1 h to remove excess silver, yielding a silicon nanowire array. The silicon nanowire array was observed under a scanning electron microscope, and the results are as follows: Figure 2 As shown.

[0072] Step 2: Hydroxylation and carboxylation treatment of silicon nanowire arrays.

[0073] Hydroxylation treatment: The silicon nanowire array was immersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide (volume ratio of concentrated sulfuric acid to hydrogen peroxide 15 mL: 5 mL) and heated under reflux for 1 h. After cleaning the nanowire array, it was immersed in a mixed solution of H2O: 30% H2O2: NH3·H2O = 10 mL: 2 mL: 2 mL (v / v / v) for 3 h. After cleaning, it was placed in a vacuum oven to dry, thus obtaining the hydroxylated silicon nanowire array.

[0074] Carboxylation treatment: 5 mL of deionized water and 100 μL of sodium carboxyethylsilanetriol were added to the hydroxylated silicon nanowire array. After thorough shaking and reaction, the array was washed with deionized water to obtain a surface-carboxylated silicon nanowire array. Individual silicon nanowires were peeled off from the array using a scraper and dispersed in 5 mL of aqueous solution. Transmission electron microscopy (TEM) images of the individual silicon nanowires are shown below. Figure 3 As shown.

[0075] Step 3: Preparation of NaYF4(Yb,Er)

[0076] 246.8 mg YCl3·6H2O, 66.7 mg YbCl3·6H2O, and 7.0 mg ErCl3·6H2O were dispersed in a 6 mL solution of oleic acid and 10 mL of octadecene, and the mixture was thoroughly sonicated. The mixture was transferred to a three-necked flask, and a vacuum was applied. When the bubbles in the flask were no longer obvious, the stirrer was turned on, and the temperature was set to 40 °C. Vacuuming and purging were performed using a double-row tube, repeated several times, to remove oxygen from the reaction vessel. Under vacuum, the temperature was raised to 120-130 °C. When the solution began to boil, the vacuuming was stopped, and the mixture was maintained in a closed system for 40-60 minutes. The temperature was then raised to 160 °C. After reaching 160 °C, the temperature was maintained for 5-10 minutes, and then the temperature was set to 40 °C and allowed to cool naturally. After cooling, 4 mmol NH4F and 1 mmol NaOH were added to the reaction solution, and the vacuuming and purging processes were continued until no obvious bubbles were observed. Insert a nitrogen balloon to protect the system under nitrogen atmosphere, heat to 300°C, and react for one hour. After the reaction is complete, allow it to cool naturally. Pour the reaction product into a centrifuge tube, centrifuge at 10000 rpm for 10 minutes, and remove the supernatant.

[0077] First wash: The reaction product was ultrasonically dispersed in a cyclohexane:ethanol (1:1 v:v) mixture, followed by centrifugation to precipitate. The washing was repeated, and finally, the bottom precipitate was dispersed in 10 mL of cyclohexane.

[0078] Secondary washing: Prepare an ethanol:water (1:4 v:v) mixed solution and adjust the pH of the mixed solution to 0 with hydrochloric acid. The product from the first washing is centrifuged and redispersed in the mixed solution. After centrifugation to remove the supernatant, it is further dissolved in the mixed solution and ultrasonically dispersed. After multiple centrifugations and removal of the supernatant, the final precipitate is dispersed in the mixed solution and thoroughly shaken for 12 hours at a speed of 500 r / min to obtain NaYF4(Yb,Er) (where the molar content of Yb is approximately 17% and the molar content of Er is approximately 1.8%). Its transmission electron microscopy image is shown below. Figure 4 As shown, the X-ray diffraction energy spectrum is as follows: Figure 5 As shown, the fluorescence spectrum is as follows: Figure 6 As shown (tested at high temperature 50℃ and low temperature 10℃ respectively).

[0079] Step 4: Fabrication of a single silicon nanowire fluorescence ratio thermometer

[0080] All of the NaYF4(Yb,Er) obtained in step three above was added to the aqueous dispersion of all the carboxylated monocrystalline silicon nanowires obtained in step two. The pH was adjusted to 9 with ammonia, and 100 μL of TEOS was added. The mixture was shaken thoroughly at 500 r / min for 1 h. The monocrystalline silicon nanowires were collected through a 200 μm aqueous filter and thoroughly washed with deionized water to obtain a monocrystalline silicon nanowire fluorescence ratio thermometer (see schematic diagram of preparation principle). Figure 1 ).

[0081] Depend on Figure 1 As can be seen, in step four of this example, TEOS reacts to form SiO2, which can coat NaYF4(Yb,Er) onto the surface of the entire single silicon nanowire, thereby obtaining a single silicon nanowire fluorescence ratio thermometer.

[0082] Depend on Figure 2 It can be seen that the average length of the silicon nanowires prepared in this example is 120 μm.

[0083] Depend on Figure 3 It can be seen that the diameter of the single silicon nanowire prepared in this example is 150nm-200nm.

[0084] Depend on Figure 4 It can be seen that the NaYF4(Yb,Er) particles prepared in this example are uniform, with an average diameter of 60 nm.

[0085] Depend on Figure 5 It can be seen that the NaYF4(Yb,Er) prepared in this example is β-NaYF4(Yb,Er), and the material with this crystal form has a higher quantum yield.

[0086] Example 2

[0087] Step 1: Fabrication of silicon nanowire arrays

[0088] A 1×2cm n-type silicon wafer was cut and ultrasonically cleaned for 10 min each with acetone, ethanol, and deionized water. The wafer, face up, was immersed in a mixed solution of 0.153g silver nitrate, 40mL hydrofluoric acid, and 140mL deionized water for 9 min. After removal, the wafer was cleaned and then etched at 50℃ for 120 min in a mixed solution of 40mL hydrofluoric acid, 4mL hydrogen peroxide, and 136mL deionized water. The wafer was then removed and immersed in aqua regia for 2 h to remove excess silver, yielding a silicon nanowire array. The array was observed under a scanning electron microscope; the average length of the nanowires was 120µm.

[0089] Step 2: Hydroxylation and carboxylation treatment of silicon nanowire arrays.

[0090] Hydroxylation treatment: The silicon nanowire array was immersed in a solution of concentrated sulfuric acid and hydrogen peroxide (volume ratio of concentrated sulfuric acid to hydrogen peroxide 20 mL: 5 mL) and heated under reflux for 1.5 h. After cleaning the nanowire array, it was immersed in a mixed solution of H2O: 30% H2O2: NH3·H2O = 10 mL: 2 mL: 2 mL (v / v / v) for 7 h. After cleaning, it was placed in a vacuum oven to dry, thus obtaining the hydroxylated silicon nanowire array.

[0091] Carboxylation treatment: 8 mL of deionized water and 300 μL of sodium carboxyethylsilanetriol were added to the hydroxylated silicon nanowire array. After thorough shaking and reaction, the array was washed with deionized water to obtain a surface-carboxylated silicon nanowire array. Individual silicon nanowires were peeled off from the array using a scraper and dispersed in 5 mL of aqueous solution (wherein the diameter of the individual silicon nanowires was 150 nm-200 nm).

[0092] Step 3: Preparation of NaYF4(Yb,Er)

[0093] 246.8 mg YCl3·6H2O, 66.7 mg YbCl3·6H2O, and 10 mg ErCl3·6H2O were dispersed in 8 mL of a mixed solution of oleic acid and 15 mL of octadecene, and thoroughly sonicated. The mixture was transferred to a three-necked flask, evacuated, and stirred until the bubbles in the flask were no longer obvious. The temperature was set to 40 °C. Vacuuming and purging were performed using a double-row tube, repeated several times, to remove oxygen from the reaction vessel. Under vacuum, the temperature was raised to 120-130 °C. When the solution began to boil, vacuuming was stopped, and the mixture was maintained in a closed system for 40-60 minutes. The temperature was then raised to 160 °C. After reaching 160 °C, the temperature was maintained for 5-10 minutes, and then the temperature was set to 40 °C and allowed to cool naturally. After cooling, 4 mmol NH4F and 1 mmol NaOH were added to the reaction solution, and vacuuming and purging were continued until no obvious bubbles were observed. Vacuuming was then stopped. Insert a nitrogen balloon to protect the system under nitrogen atmosphere, heat to 300°C, and react for one hour. After the reaction is complete, allow it to cool naturally. Pour the reaction product into a centrifuge tube, centrifuge at 10000 rpm for 15 minutes, and remove the supernatant.

[0094] First wash: The reaction product was ultrasonically dispersed in a cyclohexane:ethanol (1:1 v:v) mixture, followed by centrifugation to precipitate. The washing was repeated, and finally, the bottom precipitate was dispersed in 10 mL of cyclohexane.

[0095] Secondary washing: Prepare an ethanol:water (1:1 v:v) mixed solution and adjust the pH of the mixed solution to 1 with hydrochloric acid. During oleic acid removal, the product from the first washing is centrifuged and redispersed in the mixed solution. Subsequently, after centrifuging to remove the supernatant, NaYF4(Yb,Er) is further dissolved in the mixed solution and ultrasonically dispersed. After multiple centrifugations and removal of the supernatant, the final precipitate is dispersed in the mixed solution and thoroughly shaken for 18 hours at a speed of 1000 r / min to obtain NaYF4(Yb,Er) (with a molar content of approximately 17% for Yb and approximately 2.6% for Er).

[0096] Step 4: Fabrication of a single silicon nanowire fluorescence ratio thermometer

[0097] NaYF4(Yb,Er) was added to an aqueous dispersion of carboxylated silicon nanowires, the pH was adjusted to 11 with ammonia, 300 μL of TEOS was added, and the mixture was shaken thoroughly at 1000 r / min for 7 h. Single silicon nanowires were collected through a 200 μm aqueous filter and thoroughly washed with deionized water to obtain a single silicon nanowire fluorescence ratio thermometer.

[0098] Example 3

[0099] Step 1: Fabrication of silicon nanowire arrays

[0100] A 2×2cm n-type silicon wafer was cut and ultrasonically cleaned for 10 min each with acetone, ethanol, and deionized water. The wafer, face up, was then immersed in a mixed solution of 0.153g silver nitrate, 40mL hydrofluoric acid, and 140mL deionized water for 10 min. After removal, the wafer was cleaned and then etched at 60℃ for 150 min in a mixed solution of 40mL hydrofluoric acid, 4mL hydrogen peroxide, and 136mL deionized water. The wafer was then removed and immersed in aqua regia for 2 hours to remove excess silver, yielding a silicon nanowire array. The array was observed under a scanning electron microscope; the average length of the nanowires was 150µm.

[0101] Step 2: Hydroxylation and carboxylation treatment of silicon nanowire arrays.

[0102] Hydroxylation treatment: The silicon nanowire array was immersed in a solution of concentrated sulfuric acid and hydrogen peroxide (volume ratio of concentrated sulfuric acid to hydrogen peroxide 25 mL: 5 mL) and heated under reflux for 2 h. After cleaning the nanowire array, it was immersed in a mixed solution of H2O: 30% H2O2: NH3·H2O = 10 mL: 2 mL: 2 mL (v / v / v) for 10 h. After cleaning, it was placed in a vacuum oven to dry, thus obtaining the hydroxylated silicon nanowire array.

[0103] Carboxylation treatment: 10 mL of deionized water and 400 μL of sodium carboxyethylsilanetriol were added to the hydroxylated silicon nanowire array. After thorough shaking and reaction, the array was washed with deionized water to obtain a surface-carboxylated silicon nanowire array. Individual silicon nanowires were peeled off from the array using a scraper and dispersed in 5 mL of aqueous solution (wherein the diameter of the individual silicon nanowires was 150 nm-200 nm).

[0104] Step 3: Preparation of NaYF4(Yb,Er)

[0105] 246.8 mg YCl3·6H2O, 66.7 mg YbCl3·6H2O, and 7.0 mg ErCl3·6H2O were dispersed in a 10 mL solution of oleic acid and 20 mL of octadecene, and the mixture was sonicated thoroughly. The mixture was transferred to a three-necked flask, and a vacuum was applied. When the bubbles in the flask were no longer obvious, the stirrer was turned on, and the temperature was set to 40 °C. Vacuuming and purging were performed using a double-row tube, repeated several times, to remove oxygen from the reaction vessel. Under vacuum, the temperature was raised to 120-130 °C. When the solution began to boil, the vacuuming was stopped, and the mixture was maintained in a closed system for 40-60 minutes. The temperature was then raised to 160 °C. After reaching 160 °C, the temperature was maintained for 5-10 minutes, and then the temperature was set to 40 °C and allowed to cool naturally. After cooling, 4 mmol NH4F and 1 mmol NaOH were added to the reaction solution, and the vacuuming and purging processes were continued until no obvious bubbles were observed. Insert a nitrogen balloon to protect the system under nitrogen atmosphere, heat to 300°C, and react for one hour. After the reaction is complete, allow it to cool naturally. Pour the reaction product into a centrifuge tube, centrifuge at 12000 rpm for 20 minutes, and remove the supernatant.

[0106] First wash: The reaction product was ultrasonically dispersed in a cyclohexane:ethanol (1:1 v:v) mixture, followed by centrifugation to precipitate. The washing was repeated, and finally, the bottom precipitate was dispersed in 10 mL of cyclohexane.

[0107] Secondary washing: Prepare an ethanol:water (4:1 v:v) mixed solution and adjust the pH of the mixed solution to 3 with hydrochloric acid. During oleic acid removal, the product from the first washing is centrifuged and redispersed in the mixed solution. Subsequently, after centrifugation to remove the supernatant, it is further dissolved in the mixed solution and ultrasonically dispersed. After multiple centrifugations and removal of the supernatant, the final precipitate is dispersed in the mixed solution and thoroughly shaken for 24 hours at a speed of 1500 r / min to obtain NaYF4(Yb,Er).

[0108] Step 4: Fabrication of a single silicon nanowire fluorescence ratio thermometer

[0109] NaYF4(Yb,Er) was added to an aqueous dispersion of carboxylated silicon nanowires, the pH was adjusted to 14 with ammonia, 400 μL of TEOS was added, and the mixture was shaken thoroughly at 1500 r / min for 12 h. Single silicon nanowires were collected through a 200 μm aqueous filter and thoroughly washed with deionized water to obtain a single silicon nanowire fluorescence ratio thermometer.

[0110] Comparative Example 1

[0111] Same as Example 1, except that in step four, ammonia is not used to adjust the pH, and TEOS is not added. The oleic acid-free NaYF4(Yb,Er) is decoordinated and de-coordinated with the carboxyl groups on the carboxylated silicon nanowires.

[0112] Comparative Example 2

[0113] Similar to Example 1, the only difference being in step four, where NaYF4(Yb,Er) was directly added to the aqueous dispersion of the carboxylated silicon nanowire array, directly modifying the array with NaYF4(Yb,Er) particles. First, the pH was adjusted to 14 with ammonia, and 400 μL of TEOS was added. The reaction was thoroughly shaken at 1500 r / min for 12 h. After the reaction, the array was thoroughly washed with deionized water to obtain the NaYF4(Yb,Er) modified silicon nanowire array. Subsequently, the silicon nanowire array was scraped off the array using a spatula to obtain a single silicon nanowire fluorescence ratio thermometer.

[0114] Experimental Example 1

[0115] 1) The thermosensitivity of NaYF4(Yb,Er) prepared in Example 1 was determined, and the steps are as follows:

[0116] The NaYF4(Yb,Er) prepared in Example 1 was dispersed in 10 mL of cyclohexane. 100 μL of this dispersion was then added to 900 μL of cyclohexane solvent. The fluorescence spectrum was measured in a fluorescent cuvette. Figure 6 As shown, the ratio of fluorescence intensity at 525 nm to 545 nm was measured as a function of temperature. Measurements were taken three times at each temperature point from 10°C to 50°C, obtaining the ratio of fluorescence intensity at 525 nm and 545 nm, denoted as FIR. A curve showing the FIR versus temperature was plotted to obtain the temperature measurement curve, as shown below. Figure 7 As shown. The sensitivity and resolution of FIR to temperature were calculated at different temperature points, and the results are as follows. Figure 8 and Figure 9 As shown.

[0117] 2) The anti-interference ability of NaYF4(Yb,Er) prepared in Example 1 was determined, and the steps are as follows:

[0118] The method is the same as test 1), the only difference being that common intracellular interfering ions, such as Na+, are added to a series of fluorescent cuvettes. + K + Ca 2+ and Mg 2+ The final concentration was adjusted to 10 mM, and tests were conducted at 25 °C. The results are as follows: Figure 10 As shown.

[0119] 3) The fluorescence imaging capability of the single silicon nanowire prepared in Example 1 was measured, and the results are as follows: Figure 11 As shown.

[0120] 4) The fluorescence imaging capability of the single silicon nanowire fluorescence ratio thermometer prepared in Example 1 was determined, and the steps are as follows:

[0121] A single-strand silicon nanowire fluorescence ratio thermometer was observed under a laser scanning confocal microscope (LSCM). Two-photon 980nm laser excitation was used, and fluorescence spectra from 490-620nm were collected to obtain fluorescence images of the single-strand silicon nanowire fluorescence ratio thermometer. The results are as follows: Figure 12 As shown.

[0122] Select Figure 12 The fluorescence spectrum of the single-strand silicon nanowire fluorescence ratio thermometer was analyzed in LSCM, yielding the fluorescence spectrum of this single-strand silicon nanowire fluorescence ratio thermometer. The results are as follows: Figure 13 As shown.

[0123] 5) The temperature-sensitive performance of the single silicon nanowire fluorescent ratio thermometer prepared in Example 1 was determined, and the steps are as follows:

[0124] Under LSCM, a single silicon nanowire fluorescence ratio thermometer was excited using a 980 nm laser, and fluorescence spectra from 490 to 620 nm were collected. The FIR values ​​at different temperatures were measured. The FIR versus temperature curve was plotted, and the operating curve of the single silicon nanowire fluorescence ratio thermometer is shown below. Figure 14 As shown.

[0125] 6) Measure the fluorescence imaging of the single silicon nanowire fluorescence ratio thermometer of Comparative Example 1, such as... Figure 15 As shown.

[0126] 7) Measure and compare the fluorescence images of the modified NaYF4(Yb,Er) silicon nanowire array and the single silicon nanowire fluorescence ratio thermometer in Comparative Example 2, as shown below. Figure 16 As shown.

[0127] Analysis and Conclusion:

[0128] Depend on Figure 8-9 It can be seen that the relative sensitivity of temperature measurement of NaYF4(Yb,Er) prepared in Example 1 can reach 1.2%, and the temperature resolution can reach 0.3℃.

[0129] Depend on Figure 10 It can be seen that the FIR of NaYF4(Yb,Er) prepared in Example 1 remains unchanged after the addition of common interfering ions, indicating that NaYF4(Yb,Er) has strong anti-interference ability.

[0130] Depend on Figure 11It can be seen that the single silicon nanowires prepared in Example 1 can only be observed in bright-field images, and no fluorescence can be observed in fluorescence spectroscopy imaging.

[0131] Depend on Figure 12 It can be seen that the single silicon nanowire fluorescence ratio thermometer exhibits significant fluorescence under 980nm laser excitation.

[0132] Depend on Figure 13 It can be seen that the fluorescence spectrum of the single silicon nanowire fluorescence ratio thermometer is the same as that of NaYF4(Yb,Er). Figure 6 As shown in the figure, this demonstrates that we have successfully modified the surface of a single silicon nanowire with NaYF4(Yb,Er).

[0133] Depend on Figure 14 Calculations show that the relative sensitivity of the single silicon nanowire fluorescent ratio thermometer is 0.2%.

[0134] Depend on Figure 15 It can be seen that the single silicon nanowire fluorescent ratio thermometer in Comparative Example 1 did not show a significant fluorescence signal under 980nm laser irradiation. This indicates that the method of using the carboxyl groups on the surface of carboxylated silicon nanowires to decoordinate NaYF4(Yb,Er) cannot uniformly modify the surface of silicon nanowires with NaYF4(Yb,Er).

[0135] Depend on Figure 16 As can be seen, in Comparative Example 2, the top of the silicon nanowire array modified with NaYF4(Yb,Er) showed a clear fluorescence signal, but the resolution was low and there was no clear outline. The single-silicon nanowire fluorescence ratio thermometer obtained by this modification method did not show any single silicon nanowire with a fluorescence signal in the field of view; only NaYF4(Yb,Er) particles dispersed in the aqueous solution were visible. This indicates that the preparation method in Comparative Example 2 could only modify some NaYF4(Yb,Er) particles at the top of the silicon nanowire array, and could not uniformly modify the entire silicon nanowire.

[0136] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A single silicon nanowire fluorescent ratiometric thermometer characterized in that, The single silicon nanowire fluorescence ratio thermometer uses a single silicon nanowire as a substrate, and the surface of the single silicon nanowire is modified with temperature-sensitive upconversion nanoparticles; the upconversion nanoparticles are NaYF4(Yb,Er). In the NaYF4(Yb,Er), the molar content of Yb is 10-30%, and the molar content of Er is 1-5%. The preparation method of NaYF4(Yb,Er) includes the following steps: YCl3·6H2O, YbCl3·6H2O and ErCl3·6H2O were dispersed in a mixed solution of oleic acid and octadecene, and thoroughly sonicated. Under vacuum, the temperature was raised to 120℃-130℃ and maintained for 5 min-10 min. The temperature was then lowered to 30℃-40℃, and NH4F and NaOH were added. Under nitrogen atmosphere, the mixture was heated to 250℃-350℃ and reacted for 1-2 hours. The mixture was then washed.

2. The single silicon nanowire fluorescent ratiometric thermometer according to claim 1, wherein, The cleaning process includes a primary cleaning and a secondary cleaning. The primary cleaning is performed using a mixture of cyclohexane and ethanol. The secondary cleaning is performed using a mixture of ethanol and water. In the secondary cleaning, the pH of the mixture is 0-3.

3. In the single silicon nanowire fluorescent ratio thermometer according to claim 2, the volume ratio of cyclohexane to ethanol is 1:

1.

4. In the single silicon nanowire fluorescent ratio thermometer according to claim 2, the volume ratio of ethanol to water is 0.5-2:0.5-2.

5. The single silicon nanowire fluorescent ratiometric thermometer of claim 1, wherein, The length of the single silicon nanowire is 100 μm-150 μm and the diameter is 150 nm-200 nm.

6. The method of claim 1-5, wherein the single silicon nanowire fluorescent ratiometric thermometer is prepared by the steps of: Includes the following steps: Step 1: The silicon nanowire array is sequentially subjected to hydroxylation and carboxylation treatments, and after exfoliation, a single silicon nanowire with a carboxylated surface is obtained; Step 2: Prepare an aqueous dispersion of the surface-carboxylated monosilicon nanowires, add the upconversion nanoparticles, adjust the pH to 9-14 using ammonia, add tetraethyl orthosilicate, shake to react, and wash thoroughly with deionized water.

7. The production method according to claim 6, characterized by, The conditions for the oscillating reaction are: the oscillating reaction rate is 500 r / min-1500 r / min, and the oscillating reaction time is 1 h-12 h.

8. The preparation method according to claim 6, characterized in that, The hydroxylation treatment includes the following steps: immersing the silicon nanowire array in a mixed solution of concentrated sulfuric acid and hydrogen peroxide, heating and refluxing, cleaning it, then immersing it in a mixed solution of H2O, 30% H2O2 and NH3•H2O, cleaning it, and then drying it.

9. The preparation method according to claim 6, characterized in that, The carboxylation treatment includes the following steps: adding deionized water to the hydroxylated silicon nanowire array, adding sodium carboxyethylsilane triol, shaking the reaction thoroughly, and then cleaning with deionized water.

10. The application of the single silicon nanowire fluorescence ratio thermometer according to any one of claims 1-5 in detecting the temperature in micron-sized spaces.

11. Use according to claim 10, characterized in that, The micron-scale tiny spaces include the space within a single cell.

12. The use according to claim 10, characterized in that, Includes the following steps: At least one end of the single silicon nanowire fluorescence ratio thermometer is inserted into the test location within a micrometer-sized space. The silicon nanowire fluorescence ratio thermometer is then imaged using a laser scanning confocal microscope, and the fluorescence intensity ratio at wavelengths of 525 nm and 545 nm is obtained. The temperature at the test location is calculated using a standard curve. The laser excitation wavelength of the laser scanning confocal microscope is 980 nm.

13. Use according to claim 12, characterized in that, The plotting of the standard curve includes the following steps: 1) The fluorescence intensity ratio of the single silicon nanowire fluorescence ratio thermometer at different test temperatures was tested using a laser scanning confocal microscope at wavelengths of 525 nm and 545 nm, wherein the laser excitation wavelength of the laser scanning confocal microscope was 980 nm. 2) A standard curve was obtained by fitting the test temperature as the x-axis and the ratio of fluorescence intensity at wavelengths of 525 nm and 545 nm as the y-axis.

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