• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    植物還原法制備鈀納米單質(zhì)的還原率研究

    2017-12-27 09:26:19賀媛媛傅吉全
    化學(xué)與生物工程 2017年12期
    關(guān)鍵詞:還原法北京服裝學(xué)院廈門大學(xué)

    賀媛媛,傅吉全

    (北京服裝學(xué)院材料科學(xué)與工程學(xué)院,北京 100029)

    植物還原法制備鈀納米單質(zhì)的還原率研究

    賀媛媛,傅吉全*

    (北京服裝學(xué)院材料科學(xué)與工程學(xué)院,北京 100029)

    以PdCl2為鈀前驅(qū)體、銀杏葉提取液為還原劑,采用植物還原法將Pd2+從PdCl2溶液中還原出來,制備鈀納米單質(zhì);采用等離子體發(fā)射光譜分析法(ICP-AES)測定反應(yīng)溶液中殘留的Pd2+濃度,計算反應(yīng)的還原率;采用正交實驗探討PdCl2濃度、反應(yīng)溫度、反應(yīng)時間及銀杏葉提取液體積對還原率的影響。結(jié)果表明,鈀納米單質(zhì)最佳制備條件為:PdCl2濃度0.005 mol·L-1、反應(yīng)溫度80 ℃、反應(yīng)時間24 h、銀杏葉提取液體積60 mL,在此條件下,反應(yīng)的平均還原率為91.74%。證實,可以用ICP-AES對植物還原法進(jìn)行定量研究。

    植物還原法;鈀納米單質(zhì);正交實驗;還原率

    Palladium(Pd),a noble metal,has attracted much attention due to its unique small size effect[1].The catalytic potential of Pd nanoparticles(NPs) has been applied in many areas,including organic synthesis,catalytic degradation,chemical/biological sensors,hydrogen generation/storage,methane combustion,supercapacitors,and lithium ion batteries[2-5].In the past,Pd NPs have been prepared by a variety of physical and chemical methods,which require sophisticated equipment and excess chemicals,and easily cause environment contamination[6].The increased demand for preparation of Pd NPs and the emerging economic and environmental issues make people aware of the need to develop a simple,environmentally friendly,and cost-effective method.In this case,the biological processes using plants,microorganisms,enzymes,and biochemicals have been used to prepare Pd NPs as green substitutes.Among these methods,plant reduction is a method for the preparation of metal NPs under mild conditions using plant materials,which has unique properties and many advantages,including extensive availability,sustainability,chemical function,biocompatibility,and biodegradability[7].In addition to eco-friendly,the method can also control the morphology of NPs better,and provide a variety of precursor selections as reducing agents.In the biosynthesis of plant extracts,the biochemical components of leaves,flowers,bark,and roots,such as reducing sugars,terpenoids,flavonoids,swan glycosides,polyols,and amino acids,are involved in the reduction of metal ions into zero valent metals and nucleation processes,and they are treated as NPs with different sizes and shapes[8].

    For Pd NPs,the plant reduction process involves the introduction of biogenic substances into Pd2+solution leading to the reduction of Pd0and stabilizes the NPs with controlled morphological and structural characteristics.The preparation of Pd NPs by a plant reduction method is shown in Tab.1.

    Tab.1 The preparation of Pd NPs by a plant reduction method

    As shown in Tab.1,the size of the obtained Pd NPs is in the range of 3-100 nm,the products are stable and difficult to aggregate.In the above reports,the prepared Pd NPs were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM) or transmission electron microscopy(TEM),and they focused on qualitative analysis,but quantitative analysis was not performed.At present,only Li[16]had reported the measurement of reduction rate of this method,but there was no in-depth study on the influencing factors of reduction rate.

    In this study,using PdCl2as a palladium precursor,Ginkgobilobaleaves extract as a reducing-agent,we prepared palladium nano-element through reducing Pd2+from PdCl2solution by a plant reduction method.We measured the residual Pd2+concentration in the reaction solution by inductively coupled plasma atomic emission spectroscopy(ICP-AES),and calculated the reduction rate of the reaction.Moreover,we investigated the effects of PdCl2concentration,reaction temperature,reaction time,and volume ofGinkgobilobaleaves extract on the reduction rate by an orthogonal experiment.

    1 Experiment

    1.1 Materials and reagents

    Gingkgobilobaleaves were picked by ourselves.

    PdCl2was supplied by Tianjin Guangfu Fine Chemical Research Institute.Anhydrous ethanol,hydrochloric acid(HCl),and nitric acid(HNO3) were got from Beijing Chemical Plant.All reagents used in this experiment were of analytical grade.Experimental water was deionized(DI) water.

    1.2 Experimental method

    Ginkgobilobaleaves dry powder preparation:the collectedGinkgobilobaleaves were cleaned and dried,then placed in the oven at 80 ℃ for 12 h.Finally the leaves were crushed with high-speed universal crusher,and then sieved.The size of the particles was around 100 mesh,and the powders were stored in the fresh bag at room temperature for use in the future.

    Ginkgobilobaleaves extract preparation:weighting 5 g ofGinkgobilobaleaves dry powders in a conical flask,then 100 mL of DI water and 150 mL of anhydrous ethanol were added.The solution was boiled at 60 ℃ for 24 h.After it cooled down,the insoluble matter was removed by suction filtration,and the resulting supernatant was 20 g·L-1ofGinkgobilobaleaves extract.

    Pd nano-element preparation:20 g·L-1ofGinkgobilobaleaves extract was used as the reducing-agent.20 mL,40 mL,and 60 mLGinkgobilobaleaves extract were mixed with 0.01 mol·L-1,0.005 mol·L-1,and 0.001 mol·L-1PdCl2solution,respectively.Then the reaction carried out in a water bath shaker at a temperature range of 40-80 ℃.

    1.3 Characterization of Pd nano-element

    1.3.1 XRD analysis

    XRD(D8 advance model) was used for qualitative analysis of Pd nano-element.XRD is widely used in the phase analysis of catalyst,crystal structure analysis,and composition analysis.By XRD analysis,the formation of Pd nano-element single crystal can be verified.The reaction solution was heated in a crucible,and after the liquid was completely evaporated the black material obtained was used to prepare a test sample for XRD characterization and analysis.

    1.3.2 TEM analysis

    The Pd nano-element particle size and distribution were observed by TEM(Tecnai F30) directly.The Pd nano-element samples were dispersed in the ethanol solution and then the solution was dropped onto a copper grid for TEM.The size,morphology,distribution,and crystallinity of Pd nano-element were observed.

    1.4 Calculation of Pd nano-element reduction rate

    The quantitative analysis of prepared gold(Au) and silver(Ag) NPs by a plant reduction method can be studied by UV-Vis spectroscopy,because the UV-Vis spectra of the NPs have a significant surface plasmon resonance absorption peak(SPR peak),and the position,half height,and peak intensity of the absorption peak are strongly related to particle size,particle size distribution,and product concentration[17].However,there is no obvious SPR peak in Pd NPs and few quantitative studies on the preparation of Pd nano-element by a plant reduction method have been reported.In this paper,we used ICP-AES(CIROSEOP 120-800 nm) to quantitatively analyze Pd nano-element,measured the residual Pd2+concentration in the reaction solution and calculated the corresponding reduction rate.The specific operations were as follows:

    (1)Preparation of the samples for standard curve:0.01 g PdCl2powders were measured accurately and added in the beaker.After dissolved completely,the solution was transferred to 50 mL volumetric flask.5 mL of the solution was accurately quantified from the volumetric flask,then 5 mL of 0.5% HNO3was added,finally 10 mL of 100 mg·L-1PdCl2solution was prepared.The PdCl2standard solutions with concentration gradient of 1 mg·L-1,2 mg·L-1,3 mg·L-1,4 mg·L-1,5 mg·L-1were prepared in the same way using 0.5% HNO3again.

    (2) Preparation of the test sample:10 mL of Pd sol was put in a centrifuge tube and centrifuged for 10 min at 10 000 r·min-1.The appropriate supernatant was taken and added in another centrifuge tube,then it was diluted with 0.5% HNO3twice to 5 mg·L-1level,and finally the residual Pd2+concentration in the solution was measured by ICP-AES.

    The reduction rate(Q) of Pd is calculated by the following equation,wherenis the concentration of PdCl2precursor(mmol·L-1),M is the atomic weight(g·mol-1) of Pd,Nis the dilution factor,cfis the residual Pd2+concentration(mg·L-1).

    1.5 Design of orthogonal experiment

    In the preparation of Pd nano-element by a plant reduction method,many factors affect the reduction rate.In order to investigate the influencing factors comprehensively,PdCl2concentration,reaction temperature,reaction time,and volume ofGinkgobilobaleaves extract were selected as four factors.Through an orthogonal experiment method,we could explore the effects of these factors on the reduction rate,and determine a relatively high reduction rate of the process.

    2 Results and discussion

    2.1 Quantitative analysis of Pd nano-element

    ICP-AES was used for quantitative analysis.The residual Pd2+concentration in the reaction solution was measured,and the reduction rate of the reaction was calculated.The preparation conditions were optimized according to aL9(34) orthogonal experiment at the level of 4 factors and 3 levels.The results were shown in Tab.2.

    Tab.2 Results of orthogonal experiment

    As shown in Tab.2,the maximum reduction rate was 97.94% and the minimum reduction rate was 65.47%;with the increase of reaction temperature,reaction time,and volume ofGinkgobilobaleaves extract,the reduction rate increased.The reason could be that the higher temperature leaded to the faster movement rate of Pd2+in the reaction solution,it was easier to collide with the effective reduction groups inGinkgobilobaleaves extract,then the reduction reaction was accelerated,and the reduction rate increased;with the increase of volume ofGinkgobilobaleaves extract,the plant components that acted as reducing agents in solution increased,and more Pd2+were reduced,which resulted in an increase of the reduction rate;with the extension of reaction time,more and more effective reduction groups were exposed,so that the reducing-agent increased and the reduction rate increased as well.As reported in the previous paper[18],the reduction rate was not directly proportional to the precursor concentration,and the reaction rate increased with the increase of concentration;in contrast,when the concentration increased to a certain value,it would gradually inhibit the reduction reaction to generate Pd NPs.

    The results of the orthogonal experiment showed that the order of the factors that affect the reduction rate was:B>C>D>A,that was reaction temperature had the greatest effect on the reduction rate,reaction time had the second effect,and volume ofGinkgobilobaleaves extract and PdCl2concentration had little effect.Considering the change of A,B,C,and D factors in 3 levels,the optimal conditions were A2B3C3D3,that was PdCl2concentration was 0.005 mol·L-1,reaction temperature was 80 ℃,reaction time was 24 h,and volume ofGinkgobilobaleaves extract was 60 mL.

    The residual Pd2+concentration was measured by ICP-AES.The results showed that the reduction rate was 92.49% and 90.98%,respectively,and the average value was 91.74%.

    The reduction rate was not the maximum,and the reason could be that before each experiment the standard solution for standard line was not re-prepared.It also could result from the influence of the interaction of each factor in the orthogonal experiment.

    2.2 Qualitative analysis of Pd nano-element

    2.2.1 XRD analysis(Fig.1)

    As shown in Fig.1,the XRD pattern of the product showed four obvious diffraction peaks(1,2,3,and 4),which appeared at 2θ=40.5°,47.0°,66.5°,and 81.5°,respectively.Compared with Pd standard XRD pattern,the four peaks were the characteristic peaks of Pd element,and corresponded to(111),(200),(220),and(311) crystal planes of elemental Pd crystals,respectively,which proved the formation of Pd element.

    Fig.1 XRD pattern of product

    2.2.2 TEM analysis(Fig.2)

    The morphology of Pd NPs was observed from low magnification to high magnification.As shown in

    Fig.2 TEM images of product 1(a,b) and product 2(c,d)

    Fig.2a,although the particle size of Pd NPs was various,the overall distribution was relatively uniform and only a small amount of Pd NPs aggregated.As shown in Fig.2b,some Pd NPs were large and some were small.The size difference was large and the shape of Pd NPs were spherical.As shown in Fig.2c,the produced Pd NPs appeared in a rod-like structure,and a larger flattened crystal face of the particles with a relatively regular shape was amplified and obtained Fig.2d.From the high resolution lattice images above the square(square) and lower left(rod) NPs,it could be seen that there was a clear spacing between the crystal faces and two crystals formed.Through the TEM images of product 1 and product 2,the products prepared under different reduction conditions have different morphologies,which are worthy of further study.

    3 Conclusion

    Pd nano-element was prepared by reduction volume ofGinkgobilobaleaves extract successfully.The residual Pd2+concentration in the reaction solution was measured by ICP-AES.Then the reduction rate was calculated to complete the quantitative analysis.The optimal preparation conditions were obtained by an orthogonal experiment as follows:PdCl2concentration was 0.005 mol·L-1,reaction temperature was 80 ℃,reaction time was 24 h,volume ofGinkgobilobaleaves extract was 60 mL.The corresponding average reduction rate was 91.74%.The reason of the deviation might be the interaction between the factors.The influencing factors of reduction rate were as follows:reaction temperature>reaction time>volume ofGinkgobilobaleaves extract>PdCl2concentration,that is,reaction temperature had the greatest effect on the reduction rate,reaction time was the second,and volume ofGinkgobilobaleaves extract and PdCl2concentration had little effect on the reduction rate.

    [1] VISHNUKUMAR P,VIVEKANANDHAN S,MUTHURAMKUMAR S.Plant-mediated biogenic synthesis of palladium nanoparticles:recent trends and emerging opportunities[J].ChemBioEng Reviews,2017,4(1):18-36.

    [2] LEE S,LEE B,MEHMOOD F,et al.Oxidative decomposition of methanol on subnanometer palladium clusters:the effect of catalyst size and support composition[J].The Journal of Physical Chemistry C,2010,144(23):10342-10348.

    [3] ZHANG Y,XIANG Q,XU J Q,et al.Self-assemblies of Pd nanoparticles on the surfaces of single crystal ZnO nanowires for chemical sensors with enhanced performances[J].Journal of Materials Chemistry,2009,19(27):4701-4706.

    [4] ZENG Q,CHENG J S,LIU X F,et al.Palladium nanoparticle/chitosan-grafted graphene nanocomposites for construction of a glucose biosensor[J].Biosensors & Bioelectronics,2011,26(8):3456-3463.

    [5] STROBEL R,GRUNWAIDT J D,CAMENZIND A,et al.Flame-made alumina supported Pd-Pt nanoparticles:structural properties and catalytic behavior in methane combustion[J].Catalysis Letters,2005,104(1/2):9-16.

    [6] KANCHANA A,DEVARAJAN S,AYYAPPAN S R.Green synthesis and characterization of palladium nanoparticles and its conjugates fromSolanumtrilobatumleaf extract[J].Nano-Micro Letters,2010,2(3):169-176.

    [7] MOHAMMADINEJAD R,KARIMI S,IRAVANI S,et al.Plant-derived nanostructures:types and applications[J].Green Chemistry,2016,18(1):20-52.

    [8] DAUTHAL P,MUKHOPADHYAY M.Biosynthesis of palladium nanoparticles usingDelonixregialeaf extract and its catalytic activity for nitro-aromatics hydrogenation[J].Industrial & Engineering Chemistry Research,2013,52(51):18131-18139.

    [9] NADAGOUDA M N,VARMA R S.Green synthesis of silver and palladium nanoparticles at room temperature using coffee and tea extract[J].Green Chemistry,2008,10(8):859-862.

    [10] SATHISHKUMAR M,SNEHA K,KWAK I S,et al.Phyto-crystallization of palladium through reduction process usingCinnamomzeylanicumbark extract[J].Journal of Hazardous Materials,2009,171(1/2/3):400-404.

    [11] JIA L S,ZHANG Q,LI Q B,et al.The biosynthesis of palladium nanoparticles by antioxidants inGardeniajasminoidesEllis:long lifetime nanocatalysts forp-nitrotoluene hydrogenation[J].Nanotechnology,2009,20(38):385601-385610.

    [12] YANG X,LI Q B,WANG H X,et al.Green synthesis of palladium nanoparticles using broth ofCinnamomumcamphoraleaf[J].Journal of Nanoparticle Research,2010,12(5):1589-1598.

    [13] SHENY D S,PHILIP D,MATHEW J.Rapid green synthesis of palladium nanoparticles using the dried leaf ofAnacardiumoccidentale[J].Spectrochimica Acta Part A:Molecular and Biomolecular Spectroscopy,2012,91:35-38.

    [14] PETLA R K,VIVEKANANDHAN S,MISRA M,et al.Soybean(Glycinemax) leaf extract based green synthesis of palladium nanoparticle[J].Journal of Biomaterials and Nanobiotechnology,2012,3:14-19.

    [15] MOHAM K K,MANDAL B K,SIVA K K,et al.Biobased green method to synthesise palladium and iron nanoparticles usingTerminaliachebulaaqueous extract[J].Spectrochimica Acta Part A:Molecular and Biomolecular Spectroscopy,2013,102:128-133.

    [16] 李學(xué)亮.基于生物還原的鈀納米顆粒的可控合成[D].廈門:廈門大學(xué),2013.

    [17] 王文塔.還原制備金/銀納米顆粒的生物質(zhì)篩選及還原成分的初步探索[D].廈門:廈門大學(xué),2009.

    [18] 王易展.基于植物還原法的金納米顆粒的可控合成及其分離純化初探[D].廈門:廈門大學(xué),2012.

    O614.82

    A

    1672-5425(2017)12-0053-06

    猜你喜歡
    還原法北京服裝學(xué)院廈門大學(xué)
    電化學(xué)氧化還原法降解鹵代有機(jī)污染物的研究進(jìn)展
    云南化工(2021年11期)2022-01-12 06:06:10
    《“頭大”的一天》系列一
    流行色(2020年1期)2020-11-27 18:14:33
    北京服裝學(xué)院民族服飾博物館
    《野》
    流行色(2019年10期)2019-12-06 08:13:28
    An interpretation of kisses in This Side of Paradise
    還原法:文本分析的有效抓手
    廈門大學(xué)老年大學(xué)校歌
    Changeons l'indifférence des jeunes chinois!
    春秋必
    還原法制備石墨烯的研究進(jìn)展及發(fā)展趨勢
    一级,二级,三级黄色视频| 在线观看一区二区三区激情| 在线观看66精品国产| 日日爽夜夜爽网站| av网站在线播放免费| 久久精品91无色码中文字幕| 精品久久久久久久毛片微露脸| 久久毛片免费看一区二区三区| 国产一区二区三区视频了| 亚洲av成人一区二区三| 欧美成人免费av一区二区三区 | 免费看a级黄色片| 午夜激情av网站| 亚洲av成人一区二区三| xxxhd国产人妻xxx| 国产成人免费观看mmmm| 久久久久国内视频| 精品久久久久久久毛片微露脸| 80岁老熟妇乱子伦牲交| 久久久久久久国产电影| 在线十欧美十亚洲十日本专区| 777久久人妻少妇嫩草av网站| 午夜日韩欧美国产| 99国产精品99久久久久| 精品少妇内射三级| 免费在线观看视频国产中文字幕亚洲| 成人永久免费在线观看视频 | 91麻豆精品激情在线观看国产 | 91国产中文字幕| 高清黄色对白视频在线免费看| 十八禁网站网址无遮挡| 搡老岳熟女国产| 好男人电影高清在线观看| 亚洲精品国产区一区二| 曰老女人黄片| 亚洲国产欧美网| 久久ye,这里只有精品| 欧美黄色淫秽网站| cao死你这个sao货| 美女高潮到喷水免费观看| 国产成人系列免费观看| 大型黄色视频在线免费观看| 黄色a级毛片大全视频| 欧美成人午夜精品| 欧美精品av麻豆av| 性少妇av在线| 美女主播在线视频| 国产黄色免费在线视频| 国产有黄有色有爽视频| 亚洲精品国产精品久久久不卡| 国产91精品成人一区二区三区 | 亚洲av电影在线进入| 国产不卡av网站在线观看| 精品一区二区三卡| 国产男靠女视频免费网站| 中文字幕制服av| 老汉色∧v一级毛片| 成人精品一区二区免费| 黄片播放在线免费| 一本色道久久久久久精品综合| bbb黄色大片| 欧美日韩视频精品一区| av网站免费在线观看视频| 极品教师在线免费播放| 国产一区二区激情短视频| 久久久欧美国产精品| 丁香六月天网| 欧美日韩黄片免| 欧美日韩黄片免| 女同久久另类99精品国产91| 欧美性长视频在线观看| 亚洲自偷自拍图片 自拍| 一级毛片精品| 99精品在免费线老司机午夜| 久久人妻av系列| 人妻久久中文字幕网| 两人在一起打扑克的视频| 精品一区二区三区四区五区乱码| 一区在线观看完整版| 久久九九热精品免费| 狠狠狠狠99中文字幕| 久久中文字幕一级| 黑丝袜美女国产一区| 免费观看人在逋| 丝袜美腿诱惑在线| 美女高潮到喷水免费观看| 男女之事视频高清在线观看| 国产免费现黄频在线看| 欧美激情 高清一区二区三区| 丁香六月天网| 91字幕亚洲| 建设人人有责人人尽责人人享有的| 日韩中文字幕欧美一区二区| 女人爽到高潮嗷嗷叫在线视频| 久久午夜综合久久蜜桃| 成人国产av品久久久| 女警被强在线播放| 欧美精品人与动牲交sv欧美| 日韩视频一区二区在线观看| 国产精品国产av在线观看| 国产一区有黄有色的免费视频| 欧美日韩黄片免| 亚洲欧美日韩另类电影网站| 在线观看舔阴道视频| 看免费av毛片| 丰满迷人的少妇在线观看| √禁漫天堂资源中文www| 首页视频小说图片口味搜索| 在线观看免费午夜福利视频| tocl精华| 如日韩欧美国产精品一区二区三区| 中文欧美无线码| 免费人妻精品一区二区三区视频| 桃红色精品国产亚洲av| 欧美激情高清一区二区三区| 国内毛片毛片毛片毛片毛片| 黄片小视频在线播放| 少妇精品久久久久久久| 99国产极品粉嫩在线观看| 激情视频va一区二区三区| 久久国产精品影院| 国产视频一区二区在线看| 亚洲一区中文字幕在线| 99国产精品一区二区三区| 国产老妇伦熟女老妇高清| 人人妻,人人澡人人爽秒播| 人妻 亚洲 视频| 亚洲九九香蕉| 国产黄色免费在线视频| 久久精品国产99精品国产亚洲性色 | 男人操女人黄网站| 亚洲国产av新网站| 国产亚洲午夜精品一区二区久久| 亚洲欧洲精品一区二区精品久久久| 国产高清videossex| 一级毛片精品| a级毛片黄视频| 岛国在线观看网站| 手机成人av网站| 美女国产高潮福利片在线看| 亚洲一区中文字幕在线| 免费在线观看视频国产中文字幕亚洲| 久久精品亚洲精品国产色婷小说| 亚洲va日本ⅴa欧美va伊人久久| 久久精品亚洲精品国产色婷小说| 精品卡一卡二卡四卡免费| 香蕉久久夜色| 国产亚洲一区二区精品| 亚洲 国产 在线| tube8黄色片| 日本精品一区二区三区蜜桃| 成人免费观看视频高清| 精品国产乱码久久久久久男人| 亚洲九九香蕉| 亚洲精品自拍成人| 欧美人与性动交α欧美精品济南到| 人人妻人人澡人人看| 视频区图区小说| 国产精品秋霞免费鲁丝片| 久久久精品国产亚洲av高清涩受| 老司机福利观看| 欧美黄色淫秽网站| 91麻豆av在线| 91麻豆av在线| 亚洲精品久久午夜乱码| 久久 成人 亚洲| 午夜福利影视在线免费观看| 精品久久久精品久久久| 在线十欧美十亚洲十日本专区| 每晚都被弄得嗷嗷叫到高潮| 日韩视频在线欧美| 国产一区二区三区综合在线观看| 人妻一区二区av| 国产三级黄色录像| 99国产综合亚洲精品| av网站免费在线观看视频| 黄频高清免费视频| 国产精品 国内视频| 桃红色精品国产亚洲av| 亚洲天堂av无毛| 欧美性长视频在线观看| 亚洲精品一卡2卡三卡4卡5卡| 欧美人与性动交α欧美软件| 五月天丁香电影| av免费在线观看网站| 天堂俺去俺来也www色官网| 动漫黄色视频在线观看| 黄色 视频免费看| 国产深夜福利视频在线观看| av线在线观看网站| 国产野战对白在线观看| 国产xxxxx性猛交| 国产精品国产av在线观看| 亚洲男人天堂网一区| 久久久水蜜桃国产精品网| 日本黄色日本黄色录像| 女人久久www免费人成看片| 丝袜美腿诱惑在线| av网站免费在线观看视频| 在线观看免费日韩欧美大片| 久9热在线精品视频| 日本一区二区免费在线视频| 两人在一起打扑克的视频| 18禁裸乳无遮挡动漫免费视频| 精品午夜福利视频在线观看一区 | 中文字幕色久视频| 国产精品欧美亚洲77777| 国产精品一区二区免费欧美| 99国产精品99久久久久| 成人永久免费在线观看视频 | 国产免费现黄频在线看| 丝袜美腿诱惑在线| 老鸭窝网址在线观看| 欧美乱妇无乱码| 久久久精品国产亚洲av高清涩受| 美女扒开内裤让男人捅视频| 日本av手机在线免费观看| av不卡在线播放| 亚洲精品一卡2卡三卡4卡5卡| 国产无遮挡羞羞视频在线观看| 国产深夜福利视频在线观看| 国产精品香港三级国产av潘金莲| 黄片小视频在线播放| 老司机影院毛片| 大型av网站在线播放| 国产黄频视频在线观看| 久久久国产成人免费| 成人国语在线视频| av一本久久久久| 亚洲成人手机| a级毛片黄视频| 12—13女人毛片做爰片一| 亚洲欧美色中文字幕在线| 一本一本久久a久久精品综合妖精| 大香蕉久久网| 亚洲av欧美aⅴ国产| 欧美精品一区二区免费开放| 成人国产av品久久久| av免费在线观看网站| 天天躁夜夜躁狠狠躁躁| 欧美黑人精品巨大| 国产精品.久久久| 日韩视频一区二区在线观看| a级毛片在线看网站| 国产国语露脸激情在线看| 可以免费在线观看a视频的电影网站| 久久久精品94久久精品| 黄色毛片三级朝国网站| 老熟妇乱子伦视频在线观看| 美女视频免费永久观看网站| 国产在线观看jvid| 十八禁网站免费在线| 狠狠狠狠99中文字幕| 成人三级做爰电影| 又黄又粗又硬又大视频| 亚洲全国av大片| 俄罗斯特黄特色一大片| 免费看十八禁软件| 亚洲成国产人片在线观看| 两个人看的免费小视频| 色老头精品视频在线观看| 午夜视频精品福利| 国产高清激情床上av| 露出奶头的视频| a在线观看视频网站| 99久久国产精品久久久| 伦理电影免费视频| 亚洲专区字幕在线| 国产精品久久久久久精品古装| 无遮挡黄片免费观看| 欧美日本中文国产一区发布| 在线看a的网站| bbb黄色大片| 久久影院123| 色婷婷久久久亚洲欧美| 纯流量卡能插随身wifi吗| 另类亚洲欧美激情| 久久人妻福利社区极品人妻图片| 大香蕉久久成人网| 婷婷丁香在线五月| 免费一级毛片在线播放高清视频 | 黄色毛片三级朝国网站| 欧美日韩av久久| 久久人人97超碰香蕉20202| 亚洲成人国产一区在线观看| 少妇裸体淫交视频免费看高清 | 中亚洲国语对白在线视频| 99久久国产精品久久久| 久久久久久久久免费视频了| av电影中文网址| 久久久久久久大尺度免费视频| 国产免费av片在线观看野外av| 狠狠婷婷综合久久久久久88av| 免费观看a级毛片全部| 亚洲欧洲精品一区二区精品久久久| 99九九在线精品视频| 超碰97精品在线观看| 久久久精品免费免费高清| 一夜夜www| 性少妇av在线| 精品国内亚洲2022精品成人 | 精品欧美一区二区三区在线| 国产免费视频播放在线视频| 激情视频va一区二区三区| 男女无遮挡免费网站观看| 久久国产精品大桥未久av| 久久午夜亚洲精品久久| 国产精品欧美亚洲77777| 亚洲自偷自拍图片 自拍| 丝瓜视频免费看黄片| 国产欧美亚洲国产| a在线观看视频网站| 午夜久久久在线观看| 午夜福利影视在线免费观看| 午夜视频精品福利| 精品乱码久久久久久99久播| 久久久久久久久久久久大奶| av片东京热男人的天堂| 久久 成人 亚洲| 超碰97精品在线观看| 国产精品国产av在线观看| 欧美在线一区亚洲| 久久精品国产99精品国产亚洲性色 | 亚洲国产看品久久| 精品免费久久久久久久清纯 | 99热国产这里只有精品6| 欧美久久黑人一区二区| 亚洲午夜精品一区,二区,三区| 精品人妻在线不人妻| 欧美精品一区二区大全| 久久久久久亚洲精品国产蜜桃av| 国产av国产精品国产| 国产一区二区三区视频了| 亚洲第一青青草原| 大香蕉久久成人网| av天堂久久9| 国产精品久久久久久精品电影小说| 一个人免费看片子| 天天添夜夜摸| 免费不卡黄色视频| 一区二区三区国产精品乱码| 大型黄色视频在线免费观看| 黄色视频不卡| 波多野结衣一区麻豆| 天堂8中文在线网| 中文亚洲av片在线观看爽 | 男女午夜视频在线观看| 免费高清在线观看日韩| 人人妻人人澡人人看| 久久国产亚洲av麻豆专区| 三上悠亚av全集在线观看| 国产在线免费精品| 中文字幕人妻熟女乱码| 看免费av毛片| 免费在线观看影片大全网站| 十八禁网站免费在线| 亚洲人成电影观看| 国产精品一区二区在线不卡| 亚洲精品成人av观看孕妇| 另类亚洲欧美激情| 久久精品91无色码中文字幕| 午夜久久久在线观看| 9热在线视频观看99| 欧美黑人精品巨大| 久久精品91无色码中文字幕| 国产精品欧美亚洲77777| 国产精品免费视频内射| 日韩欧美一区二区三区在线观看 | 大型黄色视频在线免费观看| 亚洲精品国产精品久久久不卡| 日韩有码中文字幕| 99久久99久久久精品蜜桃| 精品亚洲成a人片在线观看| 国产一区二区三区在线臀色熟女 | 久久久久久人人人人人| 美女高潮到喷水免费观看| 一区二区av电影网| 精品国产国语对白av| 男女午夜视频在线观看| 黑丝袜美女国产一区| 日韩大片免费观看网站| 国产精品一区二区精品视频观看| 国产免费av片在线观看野外av| 久久精品成人免费网站| 久久人妻av系列| 国产一区二区三区视频了| 亚洲av电影在线进入| 久久久久视频综合| 成年版毛片免费区| 亚洲精品一二三| 后天国语完整版免费观看| 看免费av毛片| 国产深夜福利视频在线观看| 叶爱在线成人免费视频播放| 亚洲综合色网址| 激情视频va一区二区三区| 91麻豆精品激情在线观看国产 | 高清欧美精品videossex| 亚洲欧美激情在线| 性高湖久久久久久久久免费观看| 操美女的视频在线观看| 岛国在线观看网站| 91麻豆精品激情在线观看国产 | 亚洲欧美激情在线| 国产在线视频一区二区| 菩萨蛮人人尽说江南好唐韦庄| av不卡在线播放| 欧美老熟妇乱子伦牲交| 欧美乱妇无乱码| 国产免费视频播放在线视频| 欧美精品高潮呻吟av久久| 一级片免费观看大全| 欧美久久黑人一区二区| 久久久久久久大尺度免费视频| 成在线人永久免费视频| √禁漫天堂资源中文www| 国产无遮挡羞羞视频在线观看| 视频区欧美日本亚洲| 中文字幕色久视频| 亚洲欧美日韩另类电影网站| 午夜福利在线免费观看网站| 精品午夜福利视频在线观看一区 | 精品一区二区三卡| 成人手机av| 91九色精品人成在线观看| 亚洲精品久久成人aⅴ小说| 欧美亚洲 丝袜 人妻 在线| 天天躁日日躁夜夜躁夜夜| 蜜桃在线观看..| 老司机午夜十八禁免费视频| 老熟妇乱子伦视频在线观看| 十八禁网站网址无遮挡| 亚洲成国产人片在线观看| 在线观看66精品国产| 在线天堂中文资源库| 高清av免费在线| 久久婷婷成人综合色麻豆| 天堂中文最新版在线下载| 久久99热这里只频精品6学生| 国产激情久久老熟女| 看免费av毛片| 天天躁夜夜躁狠狠躁躁| 久久免费观看电影| 精品少妇内射三级| 国产av一区二区精品久久| 精品国产乱码久久久久久小说| 女性被躁到高潮视频| 啦啦啦 在线观看视频| 成人三级做爰电影| 悠悠久久av| av网站免费在线观看视频| 日日爽夜夜爽网站| 99re在线观看精品视频| 波多野结衣一区麻豆| 我要看黄色一级片免费的| 高清视频免费观看一区二区| 国产精品亚洲av一区麻豆| 亚洲三区欧美一区| 免费女性裸体啪啪无遮挡网站| 国产成人av激情在线播放| 国产精品麻豆人妻色哟哟久久| 久久性视频一级片| 亚洲专区字幕在线| 精品人妻熟女毛片av久久网站| 免费久久久久久久精品成人欧美视频| 久久人人97超碰香蕉20202| a级毛片在线看网站| 黑人操中国人逼视频| 他把我摸到了高潮在线观看 | 在线观看www视频免费| 少妇裸体淫交视频免费看高清 | 亚洲免费av在线视频| 亚洲成人免费电影在线观看| 欧美激情高清一区二区三区| 久久久久久久久免费视频了| 精品亚洲成国产av| 久久精品亚洲av国产电影网| 日韩免费高清中文字幕av| 18禁国产床啪视频网站| 精品国产一区二区久久| 少妇 在线观看| 国产精品.久久久| 法律面前人人平等表现在哪些方面| 99久久人妻综合| 汤姆久久久久久久影院中文字幕| 亚洲成人手机| 国产欧美日韩精品亚洲av| av天堂久久9| 99国产精品免费福利视频| 久久青草综合色| 亚洲精品国产精品久久久不卡| 两个人看的免费小视频| tube8黄色片| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲午夜精品一区,二区,三区| 国产精品九九99| 伦理电影免费视频| 久久久国产欧美日韩av| 国产av又大| 老司机在亚洲福利影院| 人人妻人人澡人人爽人人夜夜| 黑人猛操日本美女一级片| 日本五十路高清| 久久精品亚洲av国产电影网| 欧美性长视频在线观看| 视频区欧美日本亚洲| 国产高清国产精品国产三级| 天天影视国产精品| 国产极品粉嫩免费观看在线| 成人特级黄色片久久久久久久 | 在线观看免费日韩欧美大片| 国产精品熟女久久久久浪| 国产一区二区激情短视频| 免费av中文字幕在线| 天天躁狠狠躁夜夜躁狠狠躁| 99香蕉大伊视频| 亚洲五月色婷婷综合| 性色av乱码一区二区三区2| 久久午夜综合久久蜜桃| 午夜福利欧美成人| 色婷婷av一区二区三区视频| 欧美亚洲日本最大视频资源| 亚洲精华国产精华精| 香蕉久久夜色| 日韩三级视频一区二区三区| √禁漫天堂资源中文www| 他把我摸到了高潮在线观看 | 男人舔女人的私密视频| 桃红色精品国产亚洲av| 曰老女人黄片| 国产有黄有色有爽视频| 成人精品一区二区免费| 午夜福利,免费看| www.熟女人妻精品国产| 国产真人三级小视频在线观看| 久久久精品国产亚洲av高清涩受| 热re99久久精品国产66热6| 亚洲精华国产精华精| 又黄又粗又硬又大视频| videosex国产| 日日爽夜夜爽网站| 欧美黑人欧美精品刺激| 黑人猛操日本美女一级片| 国产又爽黄色视频| aaaaa片日本免费| 欧美日韩亚洲高清精品| 国产色视频综合| 黄色成人免费大全| av超薄肉色丝袜交足视频| 97人妻天天添夜夜摸| 国内毛片毛片毛片毛片毛片| 啦啦啦视频在线资源免费观看| 亚洲成av片中文字幕在线观看| 国产片内射在线| 久久精品国产亚洲av香蕉五月 | 国产成人免费观看mmmm| 18禁观看日本| 久久久国产成人免费| 国产精品久久久久久精品古装| 汤姆久久久久久久影院中文字幕| 午夜激情av网站| 国产成人精品久久二区二区91| 又黄又粗又硬又大视频| 成在线人永久免费视频| 中文字幕高清在线视频| 性高湖久久久久久久久免费观看| 亚洲精品久久午夜乱码| 亚洲成av片中文字幕在线观看| 精品第一国产精品| 亚洲精品一二三| 伦理电影免费视频| 考比视频在线观看| 久久久国产一区二区| 免费少妇av软件| 777米奇影视久久| 日韩成人在线观看一区二区三区| 午夜老司机福利片| 好男人电影高清在线观看| 一进一出抽搐动态| 亚洲 国产 在线| 三级毛片av免费| 久久精品国产a三级三级三级| 国产欧美日韩综合在线一区二区| 黄色 视频免费看| 成人黄色视频免费在线看| 中文亚洲av片在线观看爽 | 日本a在线网址| 免费在线观看视频国产中文字幕亚洲| 99国产综合亚洲精品| 亚洲av成人一区二区三| 国产精品一区二区在线观看99| 色综合婷婷激情| 亚洲性夜色夜夜综合| 香蕉久久夜色| 精品免费久久久久久久清纯 | 亚洲va日本ⅴa欧美va伊人久久| 久久中文字幕一级| 免费在线观看视频国产中文字幕亚洲| 少妇裸体淫交视频免费看高清 | 亚洲情色 制服丝袜| 日本精品一区二区三区蜜桃| 亚洲欧美日韩高清在线视频 | av一本久久久久| 国产一卡二卡三卡精品| 久久人妻av系列| 欧美日本中文国产一区发布| 中文字幕高清在线视频| 欧美日韩亚洲综合一区二区三区_| 一本久久精品| 久久精品国产亚洲av高清一级| 色老头精品视频在线观看| 交换朋友夫妻互换小说| 黄色成人免费大全| 成年人黄色毛片网站| 欧美 日韩 精品 国产|