• <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
    成人免费观看视频高清| 亚洲成人久久性| 在线免费观看的www视频| 欧美乱妇无乱码| 少妇熟女aⅴ在线视频| 91在线观看av| 波多野结衣高清无吗| 大香蕉久久成人网| avwww免费| 亚洲 欧美一区二区三区| 国产亚洲精品久久久久5区| www日本黄色视频网| 欧洲精品卡2卡3卡4卡5卡区| 国产在线观看jvid| www.www免费av| 99re在线观看精品视频| 熟妇人妻久久中文字幕3abv| 欧美黄色淫秽网站| 最近最新中文字幕大全免费视频| 亚洲欧美精品综合一区二区三区| 久久精品国产99精品国产亚洲性色| 亚洲av电影在线进入| 精品久久久久久,| 777久久人妻少妇嫩草av网站| 精品久久久久久成人av| 啪啪无遮挡十八禁网站| 日韩欧美一区视频在线观看| 亚洲国产精品999在线| 最近在线观看免费完整版| 亚洲国产毛片av蜜桃av| 国产伦在线观看视频一区| 熟女少妇亚洲综合色aaa.| 哪里可以看免费的av片| 欧美亚洲日本最大视频资源| 一区二区三区国产精品乱码| 在线看三级毛片| 免费观看人在逋| 最好的美女福利视频网| 欧美激情久久久久久爽电影| 99国产精品99久久久久| 后天国语完整版免费观看| av有码第一页| 嫩草影视91久久| 又黄又爽又免费观看的视频| 精品国产亚洲在线| 老鸭窝网址在线观看| 国产av不卡久久| 免费无遮挡裸体视频| xxx96com| 午夜免费鲁丝| 国产又黄又爽又无遮挡在线| 99热这里只有精品一区 | 国产高清视频在线播放一区| 黑人操中国人逼视频| 一级作爱视频免费观看| www日本黄色视频网| 最好的美女福利视频网| 国产精品久久久久久亚洲av鲁大| 不卡av一区二区三区| 亚洲国产欧美网| xxx96com| 性欧美人与动物交配| 国产欧美日韩一区二区精品| 叶爱在线成人免费视频播放| 亚洲精品国产精品久久久不卡| 草草在线视频免费看| 日韩免费av在线播放| 夜夜看夜夜爽夜夜摸| 免费在线观看视频国产中文字幕亚洲| 久久久久久久久免费视频了| 欧美日韩亚洲国产一区二区在线观看| 免费在线观看成人毛片| 色精品久久人妻99蜜桃| 一夜夜www| 午夜福利免费观看在线| 男女床上黄色一级片免费看| 国产高清激情床上av| 欧美日本亚洲视频在线播放| 亚洲美女黄片视频| 国产三级在线视频| 日韩精品青青久久久久久| 欧美成人午夜精品| 婷婷亚洲欧美| 一本综合久久免费| 国产亚洲欧美精品永久| 青草久久国产| 丝袜人妻中文字幕| 国产高清有码在线观看视频 | 香蕉久久夜色| 国产熟女xx| 麻豆一二三区av精品| 日本在线视频免费播放| 精品一区二区三区四区五区乱码| 欧美色欧美亚洲另类二区| а√天堂www在线а√下载| 免费看美女性在线毛片视频| 伊人久久大香线蕉亚洲五| 亚洲一区高清亚洲精品| 给我免费播放毛片高清在线观看| 在线观看午夜福利视频| 久久久久国内视频| 国产成人精品久久二区二区91| 男女视频在线观看网站免费 | 国产真人三级小视频在线观看| 精品不卡国产一区二区三区| 欧美乱码精品一区二区三区| 最近最新中文字幕大全电影3 | 最近最新免费中文字幕在线| 国产成人精品无人区| 最近最新免费中文字幕在线| 中文字幕另类日韩欧美亚洲嫩草| 久久中文字幕人妻熟女| 亚洲av电影在线进入| 免费看美女性在线毛片视频| 国产91精品成人一区二区三区| 欧美黑人精品巨大| 国产私拍福利视频在线观看| 在线永久观看黄色视频| av欧美777| 国产精品香港三级国产av潘金莲| 美女免费视频网站| 日韩精品青青久久久久久| 国产精品综合久久久久久久免费| 日本黄色视频三级网站网址| 国产精品一区二区精品视频观看| 又黄又爽又免费观看的视频| 婷婷亚洲欧美| 欧美国产精品va在线观看不卡| 久久久久久久久中文| 国产成人精品久久二区二区免费| 久久青草综合色| 亚洲在线自拍视频| 91老司机精品| 国产精品一区二区免费欧美| 午夜久久久在线观看| 婷婷丁香在线五月| 女人被狂操c到高潮| 老司机午夜福利在线观看视频| 两人在一起打扑克的视频| 夜夜夜夜夜久久久久| 亚洲一区高清亚洲精品| 很黄的视频免费| 国产成人一区二区三区免费视频网站| 真人一进一出gif抽搐免费| 无人区码免费观看不卡| 无人区码免费观看不卡| 精品无人区乱码1区二区| 99在线视频只有这里精品首页| 制服诱惑二区| 无人区码免费观看不卡| 国产极品粉嫩免费观看在线| 亚洲一区高清亚洲精品| 最新在线观看一区二区三区| 亚洲人成伊人成综合网2020| 国产97色在线日韩免费| 久久久国产成人精品二区| 亚洲国产中文字幕在线视频| 老司机福利观看| 成人18禁高潮啪啪吃奶动态图| 九色国产91popny在线| 夜夜躁狠狠躁天天躁| 久久 成人 亚洲| 男男h啪啪无遮挡| 日韩国内少妇激情av| 亚洲最大成人中文| 日本成人三级电影网站| 少妇 在线观看| 妹子高潮喷水视频| 黄色 视频免费看| 久久精品人妻少妇| 欧美+亚洲+日韩+国产| 午夜影院日韩av| 美女午夜性视频免费| 美女免费视频网站| 国内揄拍国产精品人妻在线 | 国产一区二区在线av高清观看| 久久久久久大精品| 叶爱在线成人免费视频播放| 18禁美女被吸乳视频| cao死你这个sao货| 18美女黄网站色大片免费观看| 日韩大码丰满熟妇| 一本一本综合久久| 18禁黄网站禁片午夜丰满| 久久久久久亚洲精品国产蜜桃av| 精品午夜福利视频在线观看一区| svipshipincom国产片| 50天的宝宝边吃奶边哭怎么回事| 一级毛片高清免费大全| 色播在线永久视频| 国产精品乱码一区二三区的特点| 黑人巨大精品欧美一区二区mp4| 12—13女人毛片做爰片一| 日本五十路高清| 草草在线视频免费看| 亚洲av成人av| 叶爱在线成人免费视频播放| 99久久无色码亚洲精品果冻| 国产av又大| 老司机福利观看| 国产激情欧美一区二区| 精品一区二区三区视频在线观看免费| 亚洲中文字幕日韩| www.自偷自拍.com| 天天躁狠狠躁夜夜躁狠狠躁| 国产成年人精品一区二区| 久久久久久久午夜电影| 搡老妇女老女人老熟妇| 久久久久九九精品影院| 亚洲欧美激情综合另类| 亚洲第一电影网av| 91在线观看av| 一级黄色大片毛片| 每晚都被弄得嗷嗷叫到高潮| 亚洲国产毛片av蜜桃av| 一二三四社区在线视频社区8| 嫩草影院精品99| 这个男人来自地球电影免费观看| 免费在线观看黄色视频的| 99久久综合精品五月天人人| 免费观看精品视频网站| 超碰成人久久| 999久久久精品免费观看国产| 午夜福利在线在线| 婷婷六月久久综合丁香| 一二三四社区在线视频社区8| 日本免费a在线| 青草久久国产| 亚洲一区高清亚洲精品| 啦啦啦观看免费观看视频高清| 中文字幕精品免费在线观看视频| 日本黄色视频三级网站网址| 村上凉子中文字幕在线| 国产精品,欧美在线| 日韩欧美免费精品| 亚洲成av人片免费观看| 少妇的丰满在线观看| 久久国产精品人妻蜜桃| 成年女人毛片免费观看观看9| 日日干狠狠操夜夜爽| 一边摸一边抽搐一进一小说| 非洲黑人性xxxx精品又粗又长| www.精华液| 色播在线永久视频| 亚洲成人免费电影在线观看| 久久久国产欧美日韩av| 在线免费观看的www视频| 香蕉丝袜av| 欧美色视频一区免费| 国产亚洲欧美精品永久| 丁香六月欧美| 精品少妇一区二区三区视频日本电影| www.自偷自拍.com| 久久精品国产亚洲av香蕉五月| 国产精品九九99| 三级毛片av免费| 9191精品国产免费久久| 国产又爽黄色视频| 国产一区二区三区在线臀色熟女| 成年人黄色毛片网站| 欧美中文综合在线视频| 在线观看舔阴道视频| ponron亚洲| 精品乱码久久久久久99久播| 欧美激情高清一区二区三区| 国产成人av教育| 91大片在线观看| 又黄又爽又免费观看的视频| 国产男靠女视频免费网站| 男女床上黄色一级片免费看| 国产成人影院久久av| 午夜久久久在线观看| 看黄色毛片网站| 亚洲电影在线观看av| 久久精品国产清高在天天线| 色精品久久人妻99蜜桃| 中出人妻视频一区二区| 欧美 亚洲 国产 日韩一| 亚洲 国产 在线| 亚洲熟妇中文字幕五十中出| 亚洲五月天丁香| 亚洲国产精品久久男人天堂| 黑人操中国人逼视频| 18禁黄网站禁片免费观看直播| 国产成人影院久久av| 欧美大码av| 精品不卡国产一区二区三区| 国产又色又爽无遮挡免费看| 亚洲七黄色美女视频| 熟女少妇亚洲综合色aaa.| 超碰成人久久| 男女午夜视频在线观看| 露出奶头的视频| 制服诱惑二区| 日本三级黄在线观看| 久久精品国产综合久久久| 久热爱精品视频在线9| 午夜福利欧美成人| 成人亚洲精品一区在线观看| 一个人观看的视频www高清免费观看 | 搞女人的毛片| 麻豆成人av在线观看| 久久久久久久久久黄片| 日韩高清综合在线| 激情在线观看视频在线高清| 国产一区二区三区视频了| 一区二区日韩欧美中文字幕| 亚洲av第一区精品v没综合| 久久久国产成人精品二区| 一级毛片精品| 中文亚洲av片在线观看爽| 亚洲片人在线观看| 精品国产乱码久久久久久男人| 国产国语露脸激情在线看| 91老司机精品| 熟女电影av网| 草草在线视频免费看| 18美女黄网站色大片免费观看| 亚洲avbb在线观看| 女性被躁到高潮视频| 国产又爽黄色视频| 欧美激情高清一区二区三区| 国产麻豆成人av免费视频| 亚洲欧美日韩高清在线视频| 一区二区三区高清视频在线| 老汉色av国产亚洲站长工具| 日韩高清综合在线| 精品欧美一区二区三区在线| 在线十欧美十亚洲十日本专区| 亚洲国产精品999在线| 天天添夜夜摸| 两人在一起打扑克的视频| 国产1区2区3区精品| 此物有八面人人有两片| 女生性感内裤真人,穿戴方法视频| 久久香蕉激情| 精品高清国产在线一区| 好男人电影高清在线观看| 免费高清视频大片| 欧美成狂野欧美在线观看| 最新美女视频免费是黄的| 亚洲精品国产区一区二| 亚洲精品色激情综合| 久久精品91无色码中文字幕| 久久国产精品人妻蜜桃| 女同久久另类99精品国产91| 日本 av在线| 免费搜索国产男女视频| 久久久久国产一级毛片高清牌| 一级a爱视频在线免费观看| avwww免费| 免费搜索国产男女视频| 国产片内射在线| 妹子高潮喷水视频| 一进一出好大好爽视频| 中亚洲国语对白在线视频| 久久久久精品国产欧美久久久| 成人特级黄色片久久久久久久| 国产三级黄色录像| 两人在一起打扑克的视频| 熟妇人妻久久中文字幕3abv| 婷婷六月久久综合丁香| 成年人黄色毛片网站| 日日爽夜夜爽网站| 99国产极品粉嫩在线观看| 日本a在线网址| 熟女少妇亚洲综合色aaa.| 免费无遮挡裸体视频| 黄色女人牲交| 久久九九热精品免费| 熟妇人妻久久中文字幕3abv| 日本免费一区二区三区高清不卡| 欧美性猛交黑人性爽| 国产视频内射| 国产免费男女视频| 日韩精品免费视频一区二区三区| 久久精品成人免费网站| 免费在线观看日本一区| 男女午夜视频在线观看| 啪啪无遮挡十八禁网站| 丁香六月欧美| 欧美日本亚洲视频在线播放| 国产精品av久久久久免费| 精品欧美一区二区三区在线| 亚洲精品一卡2卡三卡4卡5卡| 日本 av在线| 午夜精品在线福利| 久久 成人 亚洲| 亚洲真实伦在线观看| 日本a在线网址| 黄片播放在线免费| 99国产极品粉嫩在线观看| 亚洲七黄色美女视频| 法律面前人人平等表现在哪些方面| 国产精品1区2区在线观看.| 国产精品,欧美在线| 一级作爱视频免费观看| 波多野结衣巨乳人妻| 国产亚洲精品第一综合不卡| 欧美在线一区亚洲| 亚洲人成网站高清观看| 男人舔女人的私密视频| 国产伦人伦偷精品视频| 国产片内射在线| 欧美一区二区精品小视频在线| 国产精品精品国产色婷婷| 色综合欧美亚洲国产小说| 老汉色∧v一级毛片| 国产精品自产拍在线观看55亚洲| 欧美中文综合在线视频| 亚洲国产高清在线一区二区三 | 免费观看人在逋| 日本一本二区三区精品| 久久人人精品亚洲av| 狠狠狠狠99中文字幕| 欧美大码av| 亚洲av成人不卡在线观看播放网| 日本 欧美在线| 可以在线观看毛片的网站| 国产在线观看jvid| 18禁裸乳无遮挡免费网站照片 | 国产黄片美女视频| 香蕉av资源在线| 国内精品久久久久久久电影| 激情在线观看视频在线高清| 中文字幕人妻丝袜一区二区| 欧美丝袜亚洲另类 | 中文字幕高清在线视频| 免费看a级黄色片| 欧美成人性av电影在线观看| 久久热在线av| 美女免费视频网站| 1024视频免费在线观看| 国产1区2区3区精品| avwww免费| 在线观看日韩欧美| 麻豆成人av在线观看| 麻豆av在线久日| 琪琪午夜伦伦电影理论片6080| 老司机福利观看| 老司机靠b影院| 日韩大码丰满熟妇| 国产激情久久老熟女| 国产乱人伦免费视频| 久久中文看片网| 亚洲国产欧美一区二区综合| 一区二区三区国产精品乱码| 亚洲片人在线观看| 麻豆成人午夜福利视频| 在线十欧美十亚洲十日本专区| 亚洲精品色激情综合| 国产区一区二久久| 久久久久久免费高清国产稀缺| 视频区欧美日本亚洲| 黄色丝袜av网址大全| 神马国产精品三级电影在线观看 | 99精品欧美一区二区三区四区| 亚洲欧美精品综合久久99| 黄网站色视频无遮挡免费观看| 一个人免费在线观看的高清视频| 婷婷丁香在线五月| 久久婷婷成人综合色麻豆| 18禁美女被吸乳视频| 日日爽夜夜爽网站| av欧美777| 无人区码免费观看不卡| 女同久久另类99精品国产91| a级毛片a级免费在线| 亚洲欧洲精品一区二区精品久久久| 18禁观看日本| 亚洲成av人片免费观看| 日本成人三级电影网站| а√天堂www在线а√下载| 黑人欧美特级aaaaaa片| 国产亚洲精品第一综合不卡| 在线观看免费日韩欧美大片| 在线十欧美十亚洲十日本专区| 亚洲精品粉嫩美女一区| 国产激情久久老熟女| 久久欧美精品欧美久久欧美| 亚洲精品久久国产高清桃花| 韩国av一区二区三区四区| 国产精品免费一区二区三区在线| 桃色一区二区三区在线观看| 动漫黄色视频在线观看| 黄频高清免费视频| 99精品在免费线老司机午夜| 日韩精品免费视频一区二区三区| bbb黄色大片| 国产精品亚洲一级av第二区| 中文字幕另类日韩欧美亚洲嫩草| 欧美久久黑人一区二区| 亚洲第一av免费看| 亚洲一卡2卡3卡4卡5卡精品中文| 少妇熟女aⅴ在线视频| 女生性感内裤真人,穿戴方法视频| 成人亚洲精品av一区二区| 亚洲 国产 在线| 久久久久国内视频| 又黄又粗又硬又大视频| 哪里可以看免费的av片| 欧美国产日韩亚洲一区| 欧美日本亚洲视频在线播放| 给我免费播放毛片高清在线观看| 少妇熟女aⅴ在线视频| 国产亚洲欧美在线一区二区| 黄色丝袜av网址大全| 久久国产乱子伦精品免费另类| 男人操女人黄网站| 身体一侧抽搐| 1024手机看黄色片| 久久香蕉精品热| 亚洲国产欧美一区二区综合| 两性午夜刺激爽爽歪歪视频在线观看 | 窝窝影院91人妻| 88av欧美| 正在播放国产对白刺激| 久久狼人影院| 久久草成人影院| 国产av在哪里看| 国产国语露脸激情在线看| 动漫黄色视频在线观看| 国产精品 国内视频| 亚洲va日本ⅴa欧美va伊人久久| 国产精品爽爽va在线观看网站 | 777久久人妻少妇嫩草av网站| 极品教师在线免费播放| 啦啦啦韩国在线观看视频| 精品国产美女av久久久久小说| www国产在线视频色| 神马国产精品三级电影在线观看 | 国产亚洲av嫩草精品影院| 日韩国内少妇激情av| 免费高清在线观看日韩| 久久人妻av系列| 美女大奶头视频| 欧美色欧美亚洲另类二区| 自线自在国产av| 中文字幕人妻熟女乱码| 国产一区二区三区视频了| 99在线视频只有这里精品首页| 亚洲熟女毛片儿| 国产精品久久视频播放| 在线十欧美十亚洲十日本专区| 嫩草影院精品99| 丁香六月欧美| 亚洲男人天堂网一区| 正在播放国产对白刺激| 久热这里只有精品99| 欧美日韩亚洲国产一区二区在线观看| 国产又爽黄色视频| 可以免费在线观看a视频的电影网站| 国产av在哪里看| 黄色片一级片一级黄色片| 午夜视频精品福利| 后天国语完整版免费观看| 侵犯人妻中文字幕一二三四区| 午夜福利在线观看吧| 午夜激情av网站| cao死你这个sao货| 亚洲国产精品合色在线| 久久精品国产亚洲av高清一级| 亚洲一区二区三区不卡视频| 一个人免费在线观看的高清视频| 啦啦啦韩国在线观看视频| 免费在线观看完整版高清| 久久午夜综合久久蜜桃| 免费电影在线观看免费观看| 国产精品久久电影中文字幕| 巨乳人妻的诱惑在线观看| 欧美中文日本在线观看视频| 国产男靠女视频免费网站| 中文字幕精品亚洲无线码一区 | 亚洲精品久久成人aⅴ小说| 成人三级做爰电影| 97人妻精品一区二区三区麻豆 | 欧美大码av| 黄色女人牲交| 制服人妻中文乱码| 国产一卡二卡三卡精品| 黑人欧美特级aaaaaa片| 亚洲精品久久成人aⅴ小说| 亚洲精品国产一区二区精华液| 男人舔女人下体高潮全视频| 精品久久蜜臀av无| 啦啦啦免费观看视频1| 国产成人啪精品午夜网站| 一区福利在线观看| 午夜成年电影在线免费观看| 在线永久观看黄色视频| 精品久久久久久久久久久久久 | 性色av乱码一区二区三区2| 99国产精品一区二区三区| 夜夜爽天天搞| 日韩中文字幕欧美一区二区| 大香蕉久久成人网| 丝袜在线中文字幕| 日韩有码中文字幕| www.自偷自拍.com| 欧美丝袜亚洲另类 | 亚洲av成人不卡在线观看播放网| 一进一出抽搐动态| 18禁观看日本| 老司机午夜十八禁免费视频| 婷婷精品国产亚洲av在线| 亚洲免费av在线视频| 精品久久久久久,| 精品午夜福利视频在线观看一区| 亚洲国产看品久久| 午夜成年电影在线免费观看| 国产精品久久久久久精品电影 | 久久国产精品男人的天堂亚洲| 国产v大片淫在线免费观看| 亚洲国产看品久久| www.熟女人妻精品国产|