CN104761692A - Modification method for introducing carbon-carbon double bond to surface of nanometer silicon dioxide - Google Patents

Abstract

The invention relates to a modification method for introducing a carbon-carbon double bond to the surface of nanometer silicon dioxide. The modification method comprises the following steps of 1, determining content of hydroxyl on the nanometer SiO2 surface, 2, preparing an amino-modified nanometer SiO2 by a reaction of an aminosilane coupling agent and nanometer SiO2 and determining content of amino groups on the surface of the amino-modified nanometer SiO2 to determine a modification degree, and 3, grafting carbon-carbon double bonds with reaction activity to the surface of the nanometer SiO2 by a reaction of the excess carbon-carbon double bond-containing modifier and the amino-modified nanometer SiO2. The modification method can graft a certain amount of carbon-carbon double bonds with reaction activity to the nanometer SiO2 surface according demands and can control content of the grafted carbon-carbon double bonds by control of an amino modification degree.

Description

Nano-silica surface introduces the method for modifying of carbon-carbon double bond

Technical field

The present invention relates to Nano-meter SiO_2 ₂the technical field of surface modification, more particularly, the present invention relates to the method for modifying that a kind of nano-silica surface introduces carbon-carbon double bond.

Background technology

Nano silicon is a kind of nano-powder material that the output of large-scale industrial production in the world is at present the highest.Special microparticle surfaces Rotating fields and electronic energy level structure create the performance that common nanoparticle does not have.Nano-meter SiO_2 ₂because specific surface energy is high, strong, the quantum size effect of surface adsorption ability and macro quanta tunnel effect, small-size effect, and the chemical property of high temperature resistant, acid and alkali-resistance and asepsis environment-protecting, and the property such as unusual mechanics, electromagnetism, optics, calorifics and chemistry of having, be used to all conglomeraties such as biology, medicine, chemical industry, material, electronics, machinery, the energy, national defence; Especially all have a wide range of applications in fields such as polymer composite, electronic package material, plastics, coating, pigment, rubber, pottery, sizing agent, makeup, support of the catalyst and anti-biotic materials.

Nano-meter SiO_2 ₂in tridimensional network, its surface is with the hydroxyl of a large amount of different states, thus Nano-meter SiO_2 ₂chemical mobility of the surface is higher, easy and properties-correcting agent generation chemical reaction, and utilizes this special property, the much properties-correcting agent with particular functional group can be connected to Nano-meter SiO_2 ₂surface, thus realize Nano-meter SiO_2 by surface chemical modification ₂functionalization.Nano-meter SiO_2 ₂surface modifying method have esterification reaction method, modification by coupling, surfactant method, graftomer method etc.In the prior art, silane coupling agent is Nano-meter SiO_2 ₂one the most frequently used in numerous properties-correcting agent.Although the kind of silane coupling agent is more, their structure basic simlarity.The general formula of silane coupling agent can be expressed as 3 (RO) SiR, and wherein RO is alkoxy grp, and R is other organo-functional groups.Silane coupling agent is to Nano-meter SiO_2 ₂surface modification can be divided into two steps: be first the alkoxyl group generation hydrolysis reaction on silane coupling agent, obtain silicone hydroxyl; Then be the silicone hydroxyl that obtains of hydrolysis reaction and Nano-meter SiO_2 ₂the silicone hydroxyl on surface is obtained by reacting silica singly-bound, and silane coupling agent is connected to Nano-meter SiO_2 ₂surface.The silane coupling agent with different organo-functional group can be selected as required, just organo-functional group can be connected to Nano-meter SiO_2 by surface modification ₂surface.Except silane coupling agent and polymkeric substance, Nano-meter SiO_2 ₂can also by other modifier modifications a lot.In order to play desirable modified effect, can with carboxyl (-COOH), isocyanate group (-NCO) etc. can with the functional group of hydroxyl reaction.

Usually the silane coupling agent containing carbon-carbon double bond is utilized to modify nano silicon in prior art, but the carbon-carbon double bond of silica sphere is difficult to quantitative mensuration, and the reaction contained between the silane coupling agent of carbon-carbon double bond and silicon-dioxide is difficult to fully react completely, and be subject to the impact of many factors, therefore the modification degree of silica sphere carbon-carbon double bond is difficult to accurately control, but silica surface modified degree, the performance of proportionlity on matrix material of such as unmodified hydroxyl and carbon-carbon double bond has remarkably influenced, therefore be necessary very much to develop a kind of Nano-meter SiO_2 ₂surface modification degree carries out the method for fixing quantity.

Summary of the invention

In order to solve the above-mentioned technical problem existed in prior art, a kind of nano-silica surface is the object of the present invention is to provide to introduce the method for modifying of carbon-carbon double bond.Method of the present invention can control the modification degree of its carbon-carbon double bond easily.

To achieve these goals, present invention employs following technical scheme:

Nano-silica surface introduces a method of modifying for carbon-carbon double bond, it is characterized in that comprising the following steps: (1) measures Nano-meter SiO_2 ₂the content of surface hydroxyl; (2) amino silicane coupling agent and Nano-meter SiO_2 is utilized ₂be obtained by reacting amino modified Nano-meter SiO_2 ₂, measure amino modified Nano-meter SiO_2 ₂the content of surface amino groups determines modification degree; (3) properties-correcting agent of excessive carbon-carbon double bonds and amino modified Nano-meter SiO_2 is utilized ₂reaction, at described Nano-meter SiO_2 ₂on the surface grafting has the carbon-carbon double bond of reactive behavior.

Wherein, described amino silicane coupling agent is at least one in γ-aminopropyltrimethoxysilane, γ-aminopropyl triethoxysilane, phenylaminomethyl triethoxyl silane, phenylaminomethyl Trimethoxy silane, N-β (aminoethyl)-γ-aminopropyltriethoxy dimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxy diethoxy silane and N-β (aminoethyl)-γ-aminopropyl triethoxysilane.

Wherein, the properties-correcting agent of described carbon-carbon double bonds is maleic anhydride, olefin(e) acid or acrylate.As preferably, described properties-correcting agent is maleic anhydride.

Wherein, described acrylate is selected from methyl acrylate, ethyl propenoate, butyl acrylate, ethyl acrylate, methyl methacrylate, β-dimethyl-aminoethylmethacrylate, butyl methacrylate, methacrylic acid-2-ethylhexyl, Hydroxyethyl acrylate, Propylene glycol monoacrylate, glycidyl acrylate, hydroxyethyl methylacrylate, Rocryl 410, glycidyl methacrylate or a-cyanoacrylate.

Wherein, in step (2), Nano-meter SiO_2 is utilized ₂react in organic solvent with amino silicane coupling agent, with to described Nano-meter SiO_2 ₂surface is carried out amino modified.

Wherein, in step (2), temperature of reaction is 75 ~ 80 DEG C, and the reaction times is more than 12h.

Wherein, in step (3), add the properties-correcting agent of carbon-carbon double bonds first in organic solvent, after stirring and dissolving is complete, add amino modified Nano-meter SiO_2 ₂, then at 75 ~ 80 DEG C, stirring reaction is complete, can be grafted with the modified Nano SiO of the carbon-carbon double bond with reactive behavior after reaction product deionized water wash, filtration, drying ₂.

Wherein, described organic solvent is selected from anhydrous dimethyl benzene, propyl carbinol, petroleum naphtha, Virahol, methylcyclohexanone, dimethylcyclohexanon, trimethylcyclohexanone, isophorone, ritalin, vinyl acetic monomer, N, at least one in dinethylformamide, N,N-dimethylacetamide and N-Methyl pyrrolidone.

Wherein, in step (3), hydrochloric acid-ethanol nonaqueous titrations is utilized to judge amino modified Nano-meter SiO_2 ₂whether the amino on surface reacts completely.

Compared with prior art, the method for modifying of nano-silica surface introducing carbon-carbon double bond of the present invention has following beneficial effect:

Adopt method of modifying of the present invention, not only can as required at Nano-meter SiO_2 ₂the grafting that surface can be quantitative has the carbon-carbon double bond of reactive behavior, and the content of the carbon-carbon double bond in grafting can be controlled by controlling amino modified degree.

Accompanying drawing explanation

Fig. 1 is γ-aminopropyl triethoxysilane addition and Nano-meter SiO_2 ₂the graph of a relation of surface modification degree.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is described in further detail.Should be appreciated that specific embodiment described herein only for setting forth technical scheme of the present invention, and be not used in the protection domain limiting invention.

Embodiment 1

Measure Nano-meter SiO_2 ₂surface hydroxyl quantity

Adopt Grignard reagent titration measuring Nano-meter SiO_2 ₂the operation steps of surface hydroxyl quantity is as follows: 1. connect the titration apparatus shown in Fig. 1; 2. dry toluene is joined and Nano-meter SiO_2 is housed ₂filter flask in, in order to dispersed sample; Phosphorus pentoxide desiccator is opened (eudiometer closedown), to the dry 10min of the pipeline of titration apparatus, then closes moisture eliminator, in filter flask, add the CH be stored in constant pressure funnel fast ₃mgCl; 3. drainage eudiometer is adopted to collect the gas generated, until react completely; 4. blank assay: measure and do not add Nano-meter SiO_2 ₂the amount V of Shi Shengcheng gas _k.Nano-meter SiO_2 is calculated by formula 1 ₂the quantity of surface silicon hydroxyl:

$N=\frac{P\×(V-V_K)\×N_A}{R\×T\×S\×m}$ Formula 1

In formula: N-Nano-meter SiO_2 ₂the quantity of surface hydroxyl, individual/m ²; P-barometric point, Pa; V-generates the volume of gas, m ³; V _k-blank assay generates the volume of gas, m ³; N _a-Avogadro constant, individual/mol; R-gas law constant, (m ³pa)/(Kmol); T-experimental temperature, K; The specific surface area of S-sample, m ²/ g; The quality of m-sample, g.

According to above-mentioned determination of experimental method paper Nano-meter SiO_2 used ₂the quantity of surface hydroxyl, Grignard reagent used is methylmagnesium-chloride (3mol/L, is stored in tetrahydrofuran (THF), Shanghai Jing Chun biochemical technology limited-liability company), and measurement result is as table 1.Get the mean value of 4 groups of parallel laboratory tests, obtain Nano-meter SiO_2 ₂the adsorbed hydroxyl content is 1.1223mmol/g.

Table 1 Nano-meter SiO_2 ₂the adsorbed hydroxyl content

Nano-meter SiO_2 ₂the mensuration of modified surface amino groups

Utilize γ-aminopropyl triethoxysilane to Nano-meter SiO_2 ₂modifying surface, under certain condition can with Nano-meter SiO_2 ₂surface hydroxyl quantitative reaction, so just can calculate Nano-meter SiO_2 by measuring amino content ₂the degree of surface modification.

Hydrochloric acid-ethanol nonaqueous titrations can be used after reaction to measure Nano-meter SiO_2 ₂surface institute connect amino content.Titration principle and the operation steps of the method are as follows: Nano-meter SiO_2 ₂modified through γ-aminopropyl triethoxysilane, its surface with amine-based basic more weak, can not in water accurate titration amino content.Adopt thymol blue as indicator, under non-aqueous conditions, the hydrochloric acid-ethanolic soln knowing volumetric molar concentration with oneself then can accurate titration amino content.The chemical equation of drop reaction is as follows:

In 500mL dehydrated alcohol, add the concentrated hydrochloric acid that 10mL mass concentration is about 36%, be uniformly mixed.Accurately take 0.3g anhydrous sodium carbonate, be dissolved in 30mL deionized water, add tetrabromo-mcresolsulfonphthalein-methyl red mixture indicator solution that 5 mass concentrations are 1%, with the hydrochloric acid-ethanolic soln titration of preparation, color is garnet by green transition is titration end point, carries out blank test simultaneously.The volumetric molar concentration of hydrochloric acid-ethanolic soln is calculated by formula 2:

$c=\frac{m}{0.05299\×(V-V_0)}$ Formula 2

In formula: c-hydrochloric acid-ethanolic soln volumetric molar concentration, mol/L; M-anhydrous sodium carbonate quality, g; V-sample consumes the volume of hydrochloric acid-ethanolic soln, mL; V ₀-blank sample consumes the volume of hydrochloric acid-ethanolic soln, mL.

Accurately take the Nano-meter SiO_2 that a certain amount of γ-aminopropyl triethoxysilane is modified ₂sample, adds 20 ~ 30mL dehydrated alcohol, after sample dispersion is even, add the thymol blue solution that 5 mass concentrations are 1%, with the hydrochloric acid-ethanolic soln titration of known volumetric molar concentration, be titration end point when color from light yellow becomes pink, carry out blank assay simultaneously.Employing formula 3 calculates modified Nano SiO ₂the content of surface amino groups.

$C_N=\frac{c\×(V-V_0)}{m}\×100$ Formula 3

In formula: C _n-Nano-meter SiO_2 ₂surface amino groups content, mmol/g; M-Nano-meter SiO_2 ₂quality, g; The volumetric molar concentration of c-hydrochloric acid-ethanolic soln, mol/L; V-modified Nano SiO ₂consume the volume of hydrochloric acid-ethanolic soln, mL; V ₀-blank assay consumes the volume of hydrochloric acid-ethanolic soln, mL.

Temperature of reaction is on the impact of modification degree

Take 5g Nano-meter SiO_2 ₂(use before at 110.0 DEG C dry 8h), adds 1g γ-aminopropyl triethoxysilane and 80mL anhydrous dimethyl benzene, stirring reaction 48h at the temperature arranged.After reaction terminates, decompression steams unreacted γ-aminopropyl triethoxysilane and anhydrous dimethyl benzene, and reaction product is vacuum-drying 24h at the temperature of correspondence.Adopt hydrochloric acid-ethanol nonaqueous titrations to measure the amino content of its surface, calculate Nano-meter SiO_2 ₂surface modification degree.When temperature of reaction is lower, Nano-meter SiO_2 ₂surface amino groups content increases along with the rising of temperature; But continue to raise temperature of reaction, Nano-meter SiO_2 when temperature of reaction is elevated to 75.0 DEG C or more ₂the amino content on surface does not continue to increase, and γ-aminopropyl triethoxysilane and Nano-meter SiO_2 75 DEG C or more times are described ₂the reaction of surface hydroxyl is more complete.

Reaction times is on the impact of modification degree

Take 5g Nano-meter SiO_2 ₂(Nano-meter SiO_2 ₂before using at 110.0 DEG C dry 8h), add 1g γ-aminopropyl triethoxysilane and 80mL anhydrous dimethyl benzene, at 75.0 DEG C, react different time.After reaction terminates, decompression steams unreacted γ-aminopropyl triethoxysilane and anhydrous dimethyl benzene, and reaction product is vacuum-drying 24h at 80.0 DEG C.Adopt hydrochloric acid-ethanol nonaqueous titrations to measure the amino content on modified product surface, and calculate Nano-meter SiO_2 ₂conducting modification of surface hydroxy group degree.Make properties-correcting agent with γ-aminopropyl triethoxysilane, when being 12h when reacted, continue to extend the reaction times, Nano-meter SiO_2 ₂the amino content on surface does not obviously increase, and illustrates that the reaction times should control at about 12h.

Feed molar ratio is on the impact of modification degree

Found by above-mentioned experimental result, Nano-meter SiO_2 ₂compare thoroughly as solvent reaction with anhydrous dimethyl benzene at 75.0 DEG C with γ-aminopropyl triethoxysilane, the reaction times can be controlled in about 12h.So control Nano-meter SiO_2 ₂surface modification degree, can realize by controlling feed molar ratio.Take 1g Nano-meter SiO_2 ₂(use before at 110.0 DEG C dry 8h), adds γ-aminopropyl triethoxysilane and the 16mL anhydrous dimethyl benzene of different amount, at 75.0 DEG C, reacts 12h.By reaction product vacuum-drying 24h at 80.0 DEG C after reaction terminates.Adopt hydrochloric acid-ethanol nonaqueous titrations to measure the amino content of its surface, calculate Nano-meter SiO_2 ₂conducting modification of surface hydroxy group degree, result as shown in Figure 1.As shown in Figure 1, the dosage by controlling γ-aminopropyl triethoxysilane can control modified Nano-meter SiO_2 ₂the content of surface amino groups.Along with the increase of γ-aminopropyl triethoxysilane dosage, amino content increases gradually, the corresponding increase of modification degree.These results suggest that the condition by controlling modified-reaction, can realize Nano-meter SiO_2 ₂surface hydroxyl controllable modified.

Nano-meter SiO_2 ₂the introducing of surface double-bond

Take the Nano-meter SiO_2 that 1g γ-aminopropyl triethoxysilane is modified ₂, add 20mL N,N-dimethylacetamide (DMA) and make solvent, dropped to by above-mentioned solution at 20.0 DEG C in the solution containing 0.4g maleic anhydride and 20mL DMA, time for adding is 3h; At 75.0 DEG C, 12h is reacted, product deionized water wash, then vacuum-drying 24h at 70.0 DEG C after dripping.Adopt hydrochloric acid-ethanol nonaqueous titrations assaying reaction its surface there is no amino, illustrate that second step reaction is carried out completely.

Show to adopt the method for the present embodiment at Nano-meter SiO_2 by thermogravimetric analysis and Infrared spectroscopy ₂surface has connected the carbon-carbon double bond with reactive behavior.

Embodiment 2

Utilize phenylaminomethyl triethoxyl silane to substitute γ-aminopropyl triethoxysilane as different from Example 1, can obtain at Nano-meter SiO_2 equally ₂surface has connected the carbon-carbon double bond with reactive behavior, and modification degree and the addition of phenylaminomethyl triethoxyl silane are the identical linear relationship of embodiment 1, modification degree can be controlled easily by the addition controlling phenylaminomethyl triethoxyl silane.

Embodiment 3

Propyl carbinol, petroleum naphtha, Virahol, methylcyclohexanone, dimethylcyclohexanon, trimethylcyclohexanone, isophorone, ritalin, vinyl acetic monomer is utilized to substitute anhydrous dimethyl benzene wherein as there being agent solvent as different from Example 1.Can obtain at Nano-meter SiO_2 equally ₂surface has connected the carbon-carbon double bond with reactive behavior, and the addition of modification degree and phenylaminomethyl triethoxyl silane is the linear relationship of embodiment 1, can control modification degree easily by the addition controlling amino silicane coupling agent.

Embodiment 4

Methyl acrylate, ethyl propenoate, butyl acrylate, ethyl acrylate, methyl methacrylate, β-dimethyl-aminoethylmethacrylate, butyl methacrylate, methacrylic acid-2-ethylhexyl, Hydroxyethyl acrylate, Propylene glycol monoacrylate, glycidyl acrylate, hydroxyethyl methylacrylate, Rocryl 410, glycidyl methacrylate or a-cyanoacrylate is utilized to substitute maleic anhydride as different from Example 1.Can obtain at Nano-meter SiO_2 equally ₂surface has connected the carbon-carbon double bond with reactive behavior, and the addition of modification degree and phenylaminomethyl triethoxyl silane is the linear relationship of embodiment 1, can control modification degree easily by the addition controlling amino silicane coupling agent.

Claims (10)

1. nano-silica surface introduces a method of modifying for carbon-carbon double bond, it is characterized in that comprising the following steps: (1) measures Nano-meter SiO_2 ₂the content of surface hydroxyl; (2) amino silicane coupling agent and Nano-meter SiO_2 is utilized ₂be obtained by reacting amino modified Nano-meter SiO_2 ₂, measure amino modified Nano-meter SiO_2 ₂the content of surface amino groups determines modification degree; (3) properties-correcting agent of excessive carbon-carbon double bonds and amino modified Nano-meter SiO_2 is utilized ₂reaction, at described Nano-meter SiO_2 ₂on the surface grafting has the carbon-carbon double bond of reactive behavior.

2. method of modifying according to claim 1, is characterized in that: described amino silicane coupling agent is at least one in γ-aminopropyltrimethoxysilane, γ-aminopropyl triethoxysilane, phenylaminomethyl triethoxyl silane, phenylaminomethyl Trimethoxy silane, N-β (aminoethyl)-γ-aminopropyltriethoxy dimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxy diethoxy silane and N-β (aminoethyl)-γ-aminopropyl triethoxysilane.

3. method of modifying according to claim 1, is characterized in that: the properties-correcting agent of described carbon-carbon double bonds is maleic anhydride, olefin(e) acid or acrylate.

4. method of modifying according to claim 3, is characterized in that: described acrylate is selected from methyl acrylate, ethyl propenoate, butyl acrylate, ethyl acrylate, methyl methacrylate, β-dimethyl-aminoethylmethacrylate, butyl methacrylate, methacrylic acid-2-ethylhexyl, Hydroxyethyl acrylate, Propylene glycol monoacrylate, glycidyl acrylate, hydroxyethyl methylacrylate, Rocryl 410, glycidyl methacrylate or a-cyanoacrylate.

5. method of modifying according to claim 1, is characterized in that: in step (2), utilize Nano-meter SiO_2 ₂react in organic solvent with amino silicane coupling agent, wherein temperature of reaction is 75 ~ 80 DEG C, and the reaction times is more than 12h.

6. method of modifying according to claim 1, is characterized in that: in step (3), add the properties-correcting agent of carbon-carbon double bonds first in organic solvent, after stirring and dissolving is complete, adds amino modified Nano-meter SiO_2 ₂, then stirring reaction is complete at a certain temperature, can be grafted with the modified Nano SiO of the carbon-carbon double bond with reactive behavior after reaction product deionized water wash, filtration, drying ₂.

7. the method for modifying according to claim 5 or 6, it is characterized in that: described organic solvent is selected from anhydrous dimethyl benzene, propyl carbinol, petroleum naphtha, Virahol, methylcyclohexanone, dimethylcyclohexanon, trimethylcyclohexanone, isophorone, ritalin, vinyl acetic monomer, N, at least one in dinethylformamide, N,N-dimethylacetamide and N-Methyl pyrrolidone.

8. method of modifying according to claim 1, is characterized in that: in step (1), measure Nano-meter SiO_2 ₂the method of surface hydroxyl quantity comprises the following steps: 1. joined by dry toluene and Nano-meter SiO_2 is housed ₂filter flask in disperse described Nano-meter SiO_2 ₂; Then drying is carried out to the pipeline of titration apparatus, and in filter flask, add the CH be stored in constant pressure funnel fast ₃mgCl; 2. drainage eudiometer is adopted to collect the gas generated, until react completely; 3. blank assay: measure and do not add Nano-meter SiO_2 ₂the amount V of Shi Shengcheng gas _k; Be calculated as follows Nano-meter SiO_2 ₂the quantity of surface silicon hydroxyl:

$N=\frac{P\×(V-V_K)\×N_A}{R\×T\×S\×m}$

In formula: N-Nano-meter SiO_2 ₂the quantity of surface hydroxyl, individual/m ²; P-barometric point, Pa; V-generates the volume of gas, m ³; V _k-blank assay generates the volume of gas, m ³; N _a-Avogadro constant, individual/mol; R-gas law constant, (m ³pa)/(Kmol); T-experimental temperature, K; The specific surface area of S-sample, m ²/ g; The quality of m-sample, g.

9. method of modifying according to claim 1, is characterized in that: in step (3), utilize hydrochloric acid-ethanol nonaqueous titrations to judge amino modified Nano-meter SiO_2 ₂whether the amino on surface reacts completely.

10. method of modifying according to claim 1, is characterized in that: in step (2), utilize hydrochloric acid-ethanol nonaqueous titrations to measure Nano-meter SiO_2 ₂surface institute connect amino content; It comprises the following steps:

1. in 500mL dehydrated alcohol, add the concentrated hydrochloric acid that 10mL mass concentration is 36%, be uniformly mixed; Take 0.3g anhydrous sodium carbonate, be dissolved in 30mL deionized water, add tetrabromo-mcresolsulfonphthalein-methyl red mixture indicator solution that 5 mass concentrations are 1%, with the hydrochloric acid-ethanolic soln titration of preparation, color is garnet by green transition is titration end point, carries out blank test simultaneously; Be calculated as follows the volumetric molar concentration of hydrochloric acid-ethanolic soln:

$c=\frac{m}{0.05299\×(V-V_0)}$

In formula: c-hydrochloric acid-ethanolic soln volumetric molar concentration, mol/L; M-anhydrous sodium carbonate quality, g; V-sample consumes the volume of hydrochloric acid-ethanolic soln, mL; V ₀-blank sample consumes the volume of hydrochloric acid-ethanolic soln, mL;

2. amino modified Nano-meter SiO_2 is taken ₂, add dehydrated alcohol, after sample dispersion is even, adds the thymol blue solution that 5 mass concentrations are 1%, with the hydrochloric acid-ethanolic soln titration of known volumetric molar concentration, be titration end point when color from light yellow becomes pink, carry out blank assay simultaneously; Following formula is adopted to calculate modified Nano SiO ₂the content of surface amino groups:

$C_N=\frac{c\×(V-V_0)}{m}\×100$

In formula: C _n-Nano-meter SiO_2 ₂surface amino groups content, mmol/g; M-Nano-meter SiO_2 ₂quality, g; The volumetric molar concentration of c-hydrochloric acid-ethanolic soln, mol/L; V-modified Nano SiO ₂consume the volume of hydrochloric acid-ethanolic soln, mL; V ₀-blank assay consumes the volume of hydrochloric acid-ethanolic soln, mL.