CN115032183B - Device and method for measuring colloid stability and collision strength among colloid particles - Google Patents
Device and method for measuring colloid stability and collision strength among colloid particles Download PDFInfo
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Abstract
The invention belongs to the technical field of colloid detection, and relates to a device and a method for measuring colloid stability and collision strength among colloid particles, wherein the device comprises a temperature controller, a sample cell, a liquid filler and a laser Raman instrument; the sample cell is placed on the temperature controller and comprises a cell body, a transparent window arranged at the top of the cell body and a silicon wafer substrate connected to the bottom of the cell body. The measuring device provided by the invention has the advantages of simple structure, simplicity and convenience in operation, high sensitivity, no damage, rapidness, in-situ monitoring and the like based on the SERS technology, can dynamically monitor the stability of colloid in real time, and has universality. Meanwhile, the colloidal stability is quantitatively analyzed through the relation between the Raman intensity of a single 'hot spot' of the particle monolayer film and the collision behavior among particles, and the calculation method of the collision intensity among the single particles is novel, simple and quick.
Description
Technical Field
The invention belongs to the technical field of colloid detection, relates to a device and a method for measuring colloid stability and collision strength among colloid particles, and particularly relates to a device and a method for monitoring colloid stability and quantitatively analyzing based on surface enhanced Raman scattering.
Background
The development of colloid science has long history so far, all life processes occur in a colloid system, and colloid is widely researched in the fields of daily life, medicine and health, food industry, environmental protection and the like, and a systematic new subject, namely the establishment of colloid chemistry, is gradually developed. On one hand, the colloid system has strong Brownian movement due to the smaller size, is not easy to settle in a gravitational field, namely has dynamic stability; on the other hand, the particles have large specific surface area and high surface energy, so that the particles have a tendency of mutually aggregating to reduce the surface energy, thereby destroying the stability of the colloid, namely the colloid is a thermodynamically unstable system. Therefore, whether the colloidal particles are aggregated or not is a key to the colloidal stability.
Seventy years ago, derjaguin, landau, verwey and Overbeek (DLVO) proposed a theory for explaining colloidal stability in aqueous media, which has been used as one of the important models for understanding colloidal science. They state that the stable existence of a colloid under certain conditions depends on the potential of interactions between colloid particles, which is equal to the sum of the potential of van der Waals attraction (related to the distance between colloid particles) and the potential of electrostatic repulsion (caused by an electric double layer), where van der Waals attraction tends to cause particle aggregation, and an electrostatic electric double layer causes repulsive interaction to prevent particle aggregation. Whether the colloid is stable or not depends on the magnitude of the two opposing forces.
In real life, the stability of the colloid is often closely related to the development of its application. For example, most macromolecular drugs, such as proteins, polypeptides, DNA, etc., are susceptible to enzymatic degradation by themselves, and in most cases these drugs must be administered by injection or drug delivery systems (Drug Delivery System, DDS) (reference: filipe v., haweA., jiskootW.Pharmaceutical.Research,2010,27,796). Most of DDSs are colloid particles, and if the DDSs are easy to aggregate, the DDSs can cause poor drug administration effect and seriously threaten the life safety of patients. In scientific research and trace detection, metal sol is generally used as a substrate for surface enhanced raman spectroscopy, and in order to improve sensitivity in the detection process, salt substances are often added to promote aggregation of sol particles, but the addition of an aggregation agent reduces reproducibility of detection signals to a certain extent. Therefore, it is necessary to explore a method for monitoring the long-term stability of the dynamic process of colloid application, so as to ensure the quality and performance of colloid particles.
At present, the method for dynamically monitoring the colloidal stability mainly comprises a dynamic light scattering method (Dynamic Light Scattering, DLS) and a Nanoparticle tracking analysis method (Nanoparticle TrackingAnalysis, NTA), which are all based on the principle of Brownian motion to track the changes of parameters such as the particle size and distribution of colloidal particles, so as to reflect the colloidal stability.
DLS, also known as time dependent light scattering, measures the fluctuation of light intensity over time. When light passes through the colloid, the particles will undergo a light scattering phenomenon, and the brownian motion of the particles will cause fluctuations in the intensity of scattered light, with the magnitude of the fluctuations being related to the particle size. DLS is the measurement and analysis of the fluctuation amplitude to obtain information on the particle size of the particles affecting the change, thereby judging the tendency of the particles to sink with time. The instrument has three components-laser, sample cell and photodetector. The sample cell is a square tube made of glass or optically translucent disposable plastic. (Bhattacharjee S.J. control. Release,2016,235,337.)
NTA is a real-time dynamic nanoparticle detection technique. The technology combines a laser scattering microscope with a Charge Coupled Device (CCD) camera, and recognizes and tracks the motion trail of single particles under Brownian motion through NTA software 'visualization'. The core of the testing device is a particle observer which comprises a laser device and a sample chamber. The laser device comprises a laser diode for emitting a focused beam of light. The upper end of the sample chamber is provided with a detachable stainless steel top plate assembled with a glass window for observing the sample by a microscope. The bottom of the sample chamber contains a metalized optical plane, allowing the laser to propagate near the metal plane. And observing and recording the movement of the particles in the sample chamber by combining a microscope and a camera, and carrying out size measurement on each particle according to Einstein equation and combining NTA software to obtain the particle size distribution of the particles, and simultaneously, providing the approximate concentration of the particles. (CarrB., malloyA.NanoParticle Trackinganalysis-The Nano System.2006.)
However, DLS only considers the intensity of the scattered light of spherical particles and since the intensity of the scattered light of particles is proportional to the hexagonal of the particle diameter, making this technique less sensitive to the presence of small-sized particles, a small number of large aggregates may hinder the measurement of particle size, and thus DLS is not suitable for use in non-spherical and highly polydisperse colloidal systems nor for quantitative analysis. The NTA result is strongly dependent on the update of software and the subjective judgment of professional technicians, and the information of certain particle movements is easy to ignore and emphasize when the software threshold parameter is set, so that the result reproducibility is poor, the operation is complex, the cost is high, and a large amount of professional technicians are required to be trained.
Disclosure of Invention
The invention aims at overcoming the defects of the prior art and provides a device and a method for measuring colloid stability and collision strength among colloid particles.
According to the technical scheme of the invention, the device for measuring the colloid stability comprises a temperature controller, a sample cell, a liquid filler and a laser Raman instrument; the sample cell is arranged on the temperature controller and comprises a cell body, a transparent window arranged at the top of the cell body and a substrate connected to the bottom of the cell body; the liquid adding device is communicated with the sample tank, a sample is injected into the sample tank through the liquid adding device, and the sample is colloidal particle solution with the surface modified with probe molecules; the objective lens of the laser Raman instrument is arranged right above the transparent window.
Furthermore, the substrate is a silicon wafer substrate or a monocrystalline gold wafer, so that laser focusing of the Raman instrument is facilitated, and meanwhile, light can not penetrate and a Raman signal overlapped with a probe molecule is not generated.
Further, the probe molecule is a p-mercaptobenzoic acid (MBA) molecule, p-aminophenylthiophenol (PATP) or p-nitrophenylthiophenol (PNTP); since MBA has only two characteristic peaks, the probe molecule is preferably MBA.
Further, the colloid particles are SiO 2 Colloid particles @ Ag, fe 3 O 4 Au colloidal particles, au nanoparticles, etc.
Further, as the temperature is an important factor affecting the stability of the colloid, the higher the temperature is, the more severe the movement of particles is, the more easily the particles are aggregated, the stability of the colloid is destroyed, the temperature is increased, the evaporation of the solution is accelerated, and the laser is out of focus in the SERS measurement process, so that the change of the SERS signal intensity in the solution is affected, therefore, the set temperature of the temperature controller is 20-30 ℃, and preferably 22 ℃.
Further, the transparent window is a glass window.
Further, in order to ensure that no bubbles are generated in the sample adding process, the liquid charger is a bent liquid charger and comprises a vertical section, a bent pipe section and an introduction section which are sequentially communicated, wherein the included angle between the introduction section and the horizontal plane is not more than 5 degrees, and the introduction section is communicated with the sample tank.
In a second aspect the invention provides a method of determining colloidal stability comprising the steps of,
s1: mixing and adsorbing colloidal particles with the probe molecule solution to obtain a colloidal particle solution with the surface modified with probe molecules;
s2: and observing the colloidal particle solution with the surface modified with the probe molecules by a laser Raman instrument, collecting Raman signals, and judging the stability of the colloidal particle solution with the surface modified with the probe molecules according to the Raman signals.
The principle of the invention is based on that when particles with surface plasmas in Surface Enhanced Raman Scattering (SERS) are close to each other to a certain distance (less than 10 nm), the incident light irradiates on the structure to generate a strong local electric field between the particles, and the Raman signal of probe molecules in a gap area is greatly enhanced, namely a 'hot spot' effect. In addition to the endless collisions (brownian motion) with solvent molecules, there are often also collisions between colloidal particles, forming a large number of "hot spots", where the raman signal of the molecules is greatly enhanced. According to DLVO theory, colloid stability depends on the relative magnitudes of electrostatic repulsive force potential energy and van der Waals attractive force potential energy, and the potential energy varies along with the distance variation between particles, so that particle aggregation and sedimentation are easy to cause colloid instability due to particle collision, and the colloid stability can be revealed due to the variation of Raman signal intensity based on real-time monitoring of particle collision behavior by SERS technology.
Furthermore, the colloidal particles are prepared by a seed growth method.
Further, the concentration of the probe molecule solution is 0.1-10mM.
Further, in the step S2, the judging mode is as follows: the stable baseline intensity in the raman intensity change trace graph indicates that the colloidal particle solution is stable; or estimating the collision probability among particles according to the occurrence frequency of the 'peak' of the Raman signal of the probe molecule in the Raman intensity change track graph, and when the collision probability is lower than 20%, the colloidal particle solution is relatively stable.
Concrete embodimentsIn SiO of 2 For example, the method for determining colloidal stability can be as follows:
(1) SiO preparation by seed growth method 2 Mixing and adsorbing @ Ag colloid particles with an ethanol solution of 1mM MBA molecules to obtain SiO to be detected of the surface-modified MBA probe molecules 2 A solution of Ag colloidal particles;
(2) To be measured of SiO 2 Slowly injecting the @ Ag colloidal particle solution into the sample cell from the liquid charger to ensure no bubble generation until the whole sample cell is full of the solution;
(4) And connecting the bottom of the sample tank with a temperature controller, setting the temperature to 22 ℃, transferring to a testing platform of a Raman spectrometer, focusing laser of the Raman spectrometer on the surface of a bottom silicon wafer through a glass window of the sample tank, and performing SERS measurement.
In a third aspect the present invention provides a method for determining the collision strength between colloidal particles, using the apparatus described above, comprising the steps of,
SS1: preparing a colloidal particle monolayer film modified by probe molecules, and transferring the colloidal particle monolayer film to the surface of a substrate for SERS (surface enhanced Raman scattering) test;
SS2: according to the SERS test result, calculating the Raman intensity of a single hot spot (the distance between the colloid particles is less than 10 nm);
SS3: and calculating the intensity of collision among the single colloid particles according to the Raman intensity obtained in the step SS2 and the collision time among the colloid particles.
Further, in the step SS1, the colloidal particle monolayer film modified by the probe molecule is prepared by liquid-liquid assembly; specifically, the probe can be prepared by adding an organic solvent I (oil phase) to an aqueous solution of colloidal particles and then adding an organic solvent II containing probe molecules.
Further, in step SS1, the operation of SEM (scanning electron microscope) positioning is further included before SERS test.
Further, the specific operation of the step SS2 is as follows:
determining a region with a hot spot and average SERS intensity according to the SERS test result;
calculating the diameter of a laser spot according to the numerical aperture and the excitation wavelength of the Raman test lens, and combining the diameter of the colloid particles to obtain the number of hot spots in the region where the hot spots exist;
and estimating the Raman intensity of the single hot spot according to the average SERS intensity and the number of the hot spots.
Because the collision between the 'hot spot' in the particle monolayer film and the particle in the solution is formed based on the balance of electrostatic repulsion between particles and external force, the dynamic change of the inter-particle distance in the collision process is ignored, so the intensity of the collision between the single particles is estimated through the Raman intensity of the single 'hot spot' in the particle monolayer film. For the Raman intensity of a single 'hot spot', the measurement method used by the invention is based on liquid-liquid assembly to obtain a relatively uniform particle monolayer film, and the particle monolayer film is obtained by calculation by adopting a method combining SEM positioning and SERS imaging technology. Then according to a calculation formula of the collision time of particles in the smouchowski model under the brownian motion:
wherein eta is the viscosity of the aqueous particle solution, about 9.534X 10 -4 kg·m -1 ·s -1 ρ is the density of the aqueous particle solution, about 2200 kg.m -3 R is the radius of the particle, about 450nm, giving the magnitude of the theoretical collision time between particles under experimental conditions. And finally, calculating the collision intensity among single particles based on the quantitative relation between the theoretical collision time and the test time.
Compared with the prior art, the technical scheme of the invention has the following advantages: the measuring device has the advantages of simple structure, simplicity and convenience in operation, high sensitivity, no damage, rapidness, capability of in-situ monitoring and the like based on the SERS technology, and can dynamically monitor the stability of colloid in real time and has universality. Meanwhile, the colloidal stability is quantitatively analyzed through the relation between the Raman intensity of a single 'hot spot' of the particle monolayer film and the collision behavior among particles, and the calculation method of the collision intensity among the single particles is novel, simple and quick.
Drawings
FIG. 1 is SiO 2 SEM image of Ag core-shell colloidal particles.
Fig. 2 is a schematic structural view of the device of the present invention.
FIG. 3 is a standard Raman spectrum of MBA molecules (A), 1585cm for MBA molecules at different particle concentrations -1 A Raman intensity change track diagram (B) and a particle collision probability change curve (C) under different particle concentrations.
FIG. 4 shows 1585cm of MBA molecules in glycerol with different volume fractions -1 A raman intensity variation trace graph (a), a number statistics graph (B) of raman signal "spikes" in glycerol with different volume fractions, and an inter-particle collision probability variation graph (C).
FIG. 5 is SiO 2 SEM image of monolayer film of Ag particles (A), the dashed box in A shows MBA molecules 1585cm -1 And (3) a color zone image (B) formed by characteristic peaks, and a and B region MBA molecular Raman spectrum (C) in the B.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
Example 1
1. SiO to be measured 2 Preparation of @ Ag core-shell colloidal particles
This example uses the SiO provided by this solution according to the technical scheme disclosed in Yin et al Sensors andActuators B:chemical 2 The preparation method of the Ag core-shell colloidal particles is applied to the determination of colloidal stability. SiO (SiO) 2 The particles were aminated on their surface with 3-Aminopropyl Trimethoxysilane (ATPMS) and reduced with silver ammonia ion [ Ag (NH) by formaldehyde (HCHO) using 2nm Au as nucleation site 3 ) 2 ] + Growing a continuous Ag shell layer on the surface of the particles to prepare SiO 2 Ag core-shell colloidal particles.
The method comprises the following specific steps:
2nmAu was prepared using the Duff (ref. DuffD.G., baikerA., edwards P.P.Langmuir,1993,9,2301) method.
SiO 2 The @ Ag is prepared by a seed growth method. To a certain amount of SiO 2 Dissolving the powder in 15mL ethanol, ultrasonic dispersing, adding 100 μLAPTMS solution, and stirring vigorously at room temperature24h, washing with ethanol for 3 times, dispersing in the 15mL of 2nmAu seed solution, stirring at room temperature for 24h, washing with ultrapure water for clarifying and transparentizing, dispersing in 30mL of ultrapure water, adding 20 μl of ammonia (NH) with vigorous stirring 3 ·H 2 O), and then 5mL of diluted AgNO is added dropwise at an injection rate of 20mL/min 3 Solution (125. Mu.L 1% AgNO) 3 Diluting the solution to 5 mL), adding 10 mu LHCHO solution after injection, turning the color of the solution into dark brown to indicate the formation of Ag shell, centrifugally washing for 3 times, and dispersing in 8mL of ultrapure water for later use. Referring to FIG. 1, siO is provided for the present embodiment 2 SEM image of Ag core-shell colloidal particles; wherein SiO is 2 The diameter of the @ Ag particles was about 900nm.
2. Colloidal stability measuring device
Referring to fig. 2, a schematic structural diagram of a colloidal stability measurement device is shown. The device consists of three parts, wherein the bottom end is a temperature controller, the side edge is a bent liquid feeder, and the middle is a cylindrical sample cell. The sample cell is a semi-closed cylindrical container with the inner diameter of 3cm and the height of 8mm, a glass window is assembled at the upper end, the bottom is connected with a clean silicon wafer substrate, and the side end of the sample cell is connected with a bent liquid feeder so that the upper part of the sample cell is kept horizontal; connecting the bottom of the sample tank with a temperature controller, and setting the temperature to be 22 ℃; the colloid to be measured is SiO of a surface modified para-mercaptobenzoic acid (MBA) molecule 2 @ Ag particles: siO is made of 2 Mixing and adsorbing the @ Ag colloid particles and an ethanol solution of 1mM MBA molecules to obtain SiO to be detected of the surface-modified MBA probe molecules 2 Ag colloidal particle solution. During testing, about 6mL of particle solution to be tested is slowly added through a bent liquid feeder of the sample cell, no bubble is generated until the whole sample cell is filled with the solution, laser of a Raman instrument objective lens is focused on the surface of a silicon wafer through a glass window at the top end of the sample cell, real-time observation is performed, and Raman signals of particles in the solution are collected.
SERS tracking the influence of particle concentration on colloidal stability
In this example, different concentrations of SiO of surface modified MBA molecules were injected into the same assay device 2 The effect of particle concentration on colloidal stability was measured for the Ag particle solution.
The measuring device is connected with a temperature controller to set the temperature to 22 ℃, the temperature is transferred to a sample stage of a Raman instrument, 6mL of colloidal solution with different particle concentrations is slowly added into a sample cell, then laser of a Raman instrument objective lens is focused on the surface of a silicon wafer through a window, mapping measurement of Raman signals along with time is respectively carried out, and the measurement result is shown in figure 3. Wherein, A is a standard Raman spectrum of MBA molecules, B is 1585cm of MBA molecules in different particle concentrations -1 And a Raman intensity change track graph, wherein a graph C is a change curve of collision probability among particles in different particle concentrations. As can be seen from FIG. 3, the probe molecule MBA was only 1078 and 1585cm -1 The characteristic peaks are respectively attributed to C-S stretching vibration and C-C stretching vibration of MBA. In pure water solutions, the baseline is relatively stable with no sharp peaks due to the absence of particle addition, whereas a large number of raman signal "spikes" are obtained at a particle concentration of 0.13mM, with a "spike" intensity of about 15-120cps. The method is characterized in that colloid particles are easy to collide with each other under Brownian motion to form 'hot spots', the Raman intensity of molecules at a gap is greatly enhanced, and different numbers of 'hot spots' are captured by laser spot areas, so that 'peaks' of different Raman intensity signals are generated. To further understand the collision behavior of the particles, the ratio of time of occurrence of the MBA molecules to the total test time within 2h was defined as the particle collision probability, which was estimated to be about 17.4%. Such a low probability of inter-particle collisions also accounts for the colloidal stability to some extent. As the particle concentration was reduced, the probability of inter-particle collisions gradually decreased to approach 0, and when the particle concentration was reduced to 0.01625mM, no changes in SERS intensity due to inter-particle collisions were detected almost in the laser spot region within 2 h. In contrast, at higher particle concentrations (0.26 mM), the particles in the initial solution collide with each other under Brownian motion, resulting in the appearance of a partial signal "spike" with a Raman intensity of about 15-120cps, whereas after 2000s the particle aggregates in the spot area accelerate particle sedimentation, causing an increase in baseline intensity, and continue to increase by 80cps, at which time the inter-particle collision probability is about 75.8%. This occurs because the probability of inter-particle collisions is significantly greater and the particles are more tolerant at a particle concentration of 0.26mM at the same solution volumeIs easy to gather, is settled on the surface of the substrate under the action of gravity, and is not easy to return to the solution. This phenomenon also indicates that when the particle concentration exceeds 0.13mM, particles are liable to aggregate and settle due to a remarkable increase in the probability of collision between particles, resulting in unstable colloid.
Example 2
Preparation of SiO of surface-modified MBA molecule according to the method of example 1 2 The @ Ag colloidal particles were used to determine the effect of the dispersing medium on colloidal stability.
At the same particle concentration (0.13 mM), the property of the dispersion medium, namely the solution viscosity, is changed by regulating and controlling the proportion of glycerol and water in the solvent, a series of particle solutions with different viscosities are prepared, the whole sample cell is respectively filled, and the Mapping measurement of Raman signals along with time is carried out, wherein the measurement result is shown in figure 4. Wherein A is the MBA molecule in the glycerol with different volume fractions at 1585cm -1 The raman intensity change trace graph B, C is a statistical graph of the number of raman signal peaks in glycerol with different volume fractions and a change curve of collision probability among particles. The graph shows that the viscosity of the particle aqueous solution is relatively low, the viscosity is about 0.9 mPa.s at the experimental temperature of 22 ℃ according to the standard viscosity table of water, the particles collide and disperse with each other under the Brownian motion to form a large number of hot spots, the collision probability among the particles is relatively small, namely 17.4 percent, and the colloid is relatively stable at the moment, so that SERS signal 'peak' appears. When the glycerol content in the solution increases from 10% to 40%, the viscosity of the system gradually increases from 1.2 to 3.3 mPa.s according to a standard viscosity table at 22 ℃ under the condition that the collision probability among particles gradually decreases from 10.8% to approach 0, and when the glycerol content in the solvent reaches 40%, a signal peak caused by particle collision is hardly detected in a light spot area, and the movement of particles is very difficult and corresponds to solid-phase particles. These results are all that the addition of glycerol in the solvent increases the viscosity of the system, impedes the movement of particles, reduces the van der Waals attraction between particles, is not easy to collide, and maintains the stability of the colloid to a certain extent. The effect of solution viscosity on particle movement is very pronounced.
Example 3
1.SiO 2 Preparation of monolayer particle film of @ Ag
According to the technical scheme disclosed in Reinck et al Angewandte Chemie-Internatiaonal Edition, the embodiment prepares uniform SiO by liquid-liquid assembly 2 The @ Ag particle monolayer film is applied to the measurement of the collision strength of single particles.
The method comprises the following specific steps: 2ml of SiO was taken 2 The @ Ag particle sol was added to a 5ml beaker, whereupon 0.5ml of n-hexane was slowly added. At this time, an ethanol solution of 1mmol/LMBA molecule was slowly dropped into the system, and it was observed that the particles gradually floated on the interface between the two phases. With the continuous dripping of ethanol, the particles are gradually increased and aggregated, a compact particle monolayer film structure is formed at the interface, and finally the film is transferred to the surface of a silicon wafer for SERS test.
2. Testing of individual "hot spot" raman intensities
The raman intensity of a single "hot spot" is calculated using SEM localization in combination with SERS imaging techniques. See fig. 5 for measurement results. Wherein A is SiO 2 SEM image of monolayer film of Ag particles, B is 1585cm of MBA molecules in the area of A dotted line frame -1 And a color zone image formed by characteristic peaks, wherein C is an MBA molecular Raman spectrum of an a region and a B region in B. The ideal region for SERS Mapping detection is obtained first by SEM localization. The particle film arrangement is compact and uniform in the region with the side length of about 3 μm, and the particle size is large, so that the position can be easily found again by using an optical microscope of a Raman instrument, a 3X 3 μm region is selected, and a total of 256 points are acquired by taking 200nm as a step length, wherein the points are 1585cm based on MBA molecules -1 The characteristic peaks form a color region image. Most of the areas in the graph, including the a-area, i.e. the areas not containing hot spots, show only the baseline intensity, blue or green, since no significant raman signal is captured; and the SERS activity is greatly improved in the region b where the 'hot spot' is located, and the signal of MBA molecules at the gap is greatly enhanced, so that the signal is highlighted in the whole region. The average SERS intensity at this time was known to be about 3.5cps from the b-zone SERS intensity curve, due to the raman test lens numerical aperture N A =0.6, excitation wavelength 532nm, thus laser spot diameter size is aboutd＝(1.22λ)/N A = (1.22×532)/(0.6) =1.08 μm, then the area S of the circular laser spot laser ＝π×(d/2) 2 ≈0.92μm 2 . Also due to SiO 2 The diameter of the @ Ag particles is 900nm, siO 2 Area S of @ Ag particles is approximately 0.64 μm 2 0.92 μm 2 SiO under round laser spot 2 The number of @ Ag particles was estimated to be 0.92/0.64.apprxeq.1. If approximated as SiO 2 The single-layer film of @ Ag particles is arranged in honeycomb form, and is 0.92 μm in the most ideal state 2 The circular laser spot area contains 6 "hot spots". But in reality SiO 2 The arrangement mode of the monolayer film of Ag particles is shown in a graph A, and by corresponding the blue square areas in the graph B and the graph A one by one, the number of possible 'hot spots' in the area B can be approximately determined to be 1 to 4, and for the convenience of estimation, the Raman intensity of the single 'hot spot' is approximately considered to be 3.5 cps/2=1.75 cps.
3. Calculation of the intensity of collisions between individual particles
Based on the calculation formula of the particle collision time deduced from the Smoluchowski model, the inter-particle collision time in this experiment was found to be about 0.164 mus. Since 1 "hot spot" is 1.75cps, referring to a single "hot spot" SERS effect of 1.75counts within 1s, the inter-particle collision time is 0.164 μs, and the SERS intensity of the inter-particle collision is 1.75x0.164 x 10 -6 ＝2.9×10 -7 counts。
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. The device for measuring the colloid stability is characterized by comprising a temperature controller, a sample cell, a liquid filler and a laser Raman instrument; the sample cell is arranged on the temperature controller and comprises a cell body, a transparent window arranged at the top of the cell body and a substrate connected to the bottom of the cell body; the liquid adding device is communicated with the sample tank, a sample is injected into the sample tank through the liquid adding device, and the sample is colloidal particle solution with the surface modified with probe molecules; the objective lens of the laser Raman instrument is arranged right above the transparent window.
2. The apparatus for determining colloidal stability according to claim 1, wherein the probe molecule is a paramercaptobenzoic acid molecule, a paraaminophenol or a paranitrophenol.
3. The apparatus for measuring colloidal stability according to claim 1, wherein the temperature controller is set at 20 to 30 ℃.
4. The apparatus for determining the stability of a gel of claim 1, wherein the liquid feeder is a bent liquid feeder.
5. A method for determining the stability of a gel, characterized in that the device according to any one of claims 1 to 4 is used,
s1: mixing and adsorbing colloidal particles with the probe molecule solution to obtain a colloidal particle solution with the surface modified with probe molecules;
s2: and observing the colloidal particle solution with the surface modified with the probe molecules by a laser Raman instrument, collecting Raman signals, and judging the stability of the colloidal particle solution with the surface modified with the probe molecules according to the Raman signals.
6. The method for determining colloidal stability according to claim 5, wherein the concentration of the probe molecule solution is 0.1 to 10mM.
7. A method for measuring collision strength between colloid particles is characterized by comprising the following steps,
SS1: preparing a colloidal particle monolayer film modified by probe molecules, and transferring the colloidal particle monolayer film to the surface of a substrate for SERS (surface enhanced Raman scattering) test;
SS2: according to the SERS test result, calculating the Raman intensity of the single hot spot;
SS3: and calculating the intensity of collision among the single colloid particles according to the Raman intensity obtained in the step SS2 and the collision time among the colloid particles.
8. The method for measuring collision strength between colloidal particles according to claim 7, wherein in the step SS1, the probe molecule-modified colloidal particle monolayer film is prepared by liquid-liquid assembly.
9. The method of claim 7, wherein the step SS1 further comprises SEM positioning before SERS.
10. The method for determining the collision strength between colloidal particles as set forth in claim 7, wherein said step SS2 is specifically performed as follows:
determining a region with a hot spot and average SERS intensity according to the SERS test result;
calculating the diameter of a laser spot according to the numerical aperture and the excitation wavelength of the Raman test lens, and combining the diameter of the colloid particles to obtain the number of hot spots in the region where the hot spots exist;
and estimating the Raman intensity of the single hot spot according to the average SERS intensity and the number of the hot spots.
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