Construction Of Mesoporous Silica Nanoparticles Fluorescence Sensor And Its Sensing Performance For Biothiols

Fluorescent sensors are widely used for the detection of various analytes due to their advantages such as high sensitivity,easy operation,and real-time monitoring.Fluorescent sensors can be divided into selective sensors and cross-reactive ones according to their different recognition modes.Selective fluorescent sensors usually have higher selectivity and sensitivity,while cross-reactive fluorescent sensors can distinguish and detect multiple and similar analytes based on the fluorescence responses of different sensing elements.In recent years,along the development of nanotechnology,nanoparticle-based fluorescent sensors are getting increasing attention because of their particular properties(e.g.tunable size and shape,high specific surface area and unique optical properties).Nanoparticle-based fluorescent sensors include carbon quantum dots,polymer dots,up-conversion nanoparticles,gold nanoparticles,and mesoporous silica nanoparticles.Mesoporous silica nanoparticles have been favored by researchers due to their advantageous properties like easy synthesis,nontoxicity and optical inertness.At present,the synthesis of mesoporous silica-based fluorescent nanosensors is mainly through three pathways including“grafting”,“co-condensation”and“production of periodic mesoporous organosilicas”?to immobilize organic functionalities on the solid surface.The developed silica nanoparticle sensors have been widely used to detect some harmful metal ions and toxic analytes.Biothiols are widely involved in a series of physiological processes in living organisms.The abnormal level of biothiols may lead to some serious diseases such as Alzheimer's disease,Down's syndrome and Diabetes.Therefore,it is important to detect and identify biothiols.So far,there are few reports on fluorescent nanosensors based on mesoporous silica nanoparticles for sensing biothiols.In this dissertation,fluorescent nanosensors based on mesoporous silica nanoparticles for selective and discriminative sensing biothiols were constructed and their sensing performance were studied.Two particular types of nanosensors were developed as follows:In the first work,mesoporous silica nanoparticle was used as solid support and its surface was modified by fluorophores through two consecutive steps.The first step is to immobilize NCO-terminated silanes on the surface of silica nanoparticles,then pyronine derivative,which can react with H2S,was chemically bound to the surface of silica nanoparticles through the specific chemical reaction between NCO and amino group in PYR to obtain the fluorescent nanosensor M-SiO2@PYR.TEM,BET,FT-IR,TGA and XPS measurements approve the chemical immobilization of PYR on the mesoporous inner surface of silica nanoparticles.The fluorescent nanosensor displayed a typical pyronine emission band in aqueous solution and showed a significant fluorescence quenching response to the presence of H2S with a low detection limit of 103.6 nM.Differently,it exhibited negligible responses to other similar analytes,illustrating a high selectivity and sensitivity to H2S.Moreover,the detection of H2S could be realized in biofluids like human serum and urine,indicating the potential application of the fluorescent nanosensor in biological system.In the second work,two silanized fluorophores,NAA and RB-2,were obtained by derivatizing fluorophore naphthalene and rhodamine B with silane reagents.They were then chemically bound to the surface of mesoporous silica nanoparticles through surface reaction to obtain the dual-fluorophore functionalized nanoparticle M-SiO2@RB-NAA.TEM,BET,FT-IR,TGA and XPS measurements were carried out to approve the fluorophores naphthalene and rhodamine B were chemically attached to the mesoporous inner surface.Fluorescence measurements revealed that fluorescent nanoparticles displayed typical naphthalene and rhodamine B emission bands,where the naphthalene units exhibited weak fluorescence emission due to the modification of 2,4-dinitrobenzenesulfonyl group on naphthalene unit.The reaction with biothiols led to departure of 2,4-dinitrobenzenesulfonyl group and thereby recovered the fluorescence of naphthalene unit.It was found that the presence of different biothiols resulted in different extents of fluorescence changes of naphthalene and rhodamine B.When the fluorescent nanoparticles were tested at different concentration,its two signals responded differently to the same biothiol.Thus,in this work,this fluorescent nanoparticle with two different concentrations was used as sensing element to construct a two-element sensor array.By collecting the four signals of the two sensing elements,the fingerprint response and discrimination of the four biothiols(H2S,Cys,Hcy,GSH)were realized in aqueous solution and human serum.This work expands the detection range of analytes and realized discrimination function of fluorescent nanosensors based on mesoporous silica nanoparticles.