Intramolecular Charge Transfer Dual Fluorescence pH Sensing using p-Dibutylaminobenzoic Acid-β-cyclodextrin Inclusion Complex

The intramolecular charge transfer dual fluorescence of p-dibutylaminobenzoic acid-b-cyclodextrin inclusion complex showed a substantially higher sensitivity toward aqueous solution pH variation when compared with that of p-dibutylaminobenzoic acid alone, which established a new principle for direct CT fluorescence sensing in aqueous solution by using the CT fluorophore-cyclodextrin inclusion complex.

Study on the Tin Oxide Sol-Gel Membrane as a pH Sensing Electrode

In this study,tin oxide sensing membrane was derived by sol-gel method and was coated onto indium tin oxide (ITO) glass substrate by spin-coating technique to fabricate a pH sensing electrode.Besides,the morphology of the tin oxide membrane has been discussed through the instrumental analysis.Furthermore,the sensing characteristics of the pH electrode was measured by commercial instrumental amplifier as the readout circuit.Owing to the sol-gel method has many advantages such as easy fabrication of gel solution,ability to dope other materials without any expensive fabricating equipment.Hence,it is suitable for the mass production of a disposable sensor.

Gold Nanoparticle-based Colorimetric Sensor for pH Sensing

We present a newly designed colorimetric sensor sensitive to pH value based on a gold nanocomposite composed of gold nanoparticles and pH-sensitive polymer{dodecylthioether end functionalized poly[2-（diethylamino） ethyl methacrylate], poly（DEAEMA）-DDT}. We have shown that this design can produce stable GNP precipitate under weakly basic condition（pH=7.5） and this precipitate can be dispersed in acidic solution（pH=4.0）, due to the 2-（diethylamino） ethyl methacrylate protonated by H＋. The precipitation-dispersion process is reversible and accompanied by distinct color change that are clearly visible to the naked eye. This development may have application in the controlled fabrication of reversible pH-sensitive nanostructures and/or devices.

A series of simple curcumin-derived colorimetric and fluorescent probes for ratiometric-pH sensing and cell imaging

Colorimetric and fluorescent probes have emerged as a potent tool for pH sensing due to easy operation and high sensitivity.However,most of the existing bimodal probes require complicated synthesis,which greatly limits their wide applications.Herein,a simple fluorescent dye(called BFCUR)featuring a D-π-A-π-D conjugated system was developed from the natural polyphenol curcumin(CUR).BFCUR exhibited significant red-shift in UV absorption and fluorescence emission as pH increased because of the deprotonation of the phenolic hydroxyl groups,which resulted in the enhanced intramolecular charge transfer(ICT).The ratiometric pH detection of BFCUR was achieved with remarkable accuracy by monitoring both the absorbance ratio A;/A;and the fluorescence intensity ratio I;/I;under various pH values.In addition,the clear color changes of BFCUR under different pH conditions were visible,which enabled BFCUR to be used in test strips for rapid,visual pH detection.Moreover,BFCUR exhibited low cytotoxicity,and was successfully applied for intracellular pH detection,where the fluorescence intensity was linearly related to pH value.This study highlighted the great potential of CUR-derived BFCUR as colorimetric and fluorescent probes for ratiometric-pH sensing and cell imaging.

Mesoporous Bioactive Glass Functionalized with AIEgens for pH Sensing and Drug Delivery

Multifunctional materials combining fluorescence for drug delivery have been successfully developed by post grafted Aggregation-Induced Emission luminogens （AIEgens） onto Mesoporous Bioactive Glass （MBG）. The synthesized hybrid materials combine porous structure of MBG and strong luminescence of AIEgens, showing ordered two-dimensional hexagonal mesostructure and strong blue emission. It is worth noting that the emission color of the hybrid materials can reversible cycled between blue and yellow by changing the pH value of water solution. More importantly, the hybrid materials exhibit a drasti- cally improved apatite forming ability by soaked in Simulated Body Fluid （SBF）. Furthermore, the hybrid materials can be used for site-specific delivery of doxorubicin hydrochloride （DOX） triggered by the mildly acidic pH environment, suggesting that the AIEgens functionalized mesoporous bioactive glass have great potential applications as drug-loading biomaterial for im- aging guided therapy.

AgInS_(2)/ZnS quantum dots for noninvasive cervical cancer screening with intracellular pH sensing using fluorescence lifetime imaging microscopy

Intracellular pH plays a critical role in biological functions,and abnormal pH values are related to various diseases.Here,we report on an intracellular pH sensor AgInS_(2)(AIS)/ZnS quantum dots(QDs)that show long fluorescence lifetimes of hundreds of nanoseconds and low toxicity.Fluorescence lifetime imaging microscopy(FLIM)combined with AIS/ZnS QDs is used for the imaging of live cells in different pH buffers and different cell lines.The FLIM images of AIS/ZnS QDs in live cells demonstrate different intracellular pH values in different regions,such as in lysosomes or cytoplasm.This method can also distinguish cancer cells from normal cells,and the fluorescence lifetime difference of the AIS/ZnS QDs between the two types of cells is 100±7 ns.Most importantly,the exfoliated cervical cells from 20 patients are investigated using FLIM combined with AIS/ZnS QDs.The lifetime difference value between the normal and cervical cancer(CC)groups is 115±9 ns,and the difference between the normal and the precancerous lesion group is 64±9 ns.For the first time,the noninvasive method has been used for cervical cancer screening,and it has shown great improvement in sensitivity compared with a clinical conventional cytology examination.

Detection mechanism and classification of design principles of peroxidase mimic based colorimetric sensors: A brief overview

Synthesis and characterization of enzyme mimics with characteristic stability and high catalytic efficiency is an interesting field for researchers.Especially,with the development of nanoscience and introducing of Fe3O4 magnetic nanoparticles as peroxidase mimics in 2007,various nanomaterials such as noble metals,metal oxides,and carbon materials were introduced as enzyme mimics(nanozymes).Various nanomaterials exhibit peroxidaselike activity,hence,most of the nanozymes are peroxidase mimetics.Although the nanozyme based sensors were previously classified,the classifications have been focused on the type of nanozyme action.Therefore,the nanozyme based sensors were classified as peroxidase,hydrolase,and urease mimic-based sensors.However,heretofore,these sensors are not classified based on the detection mechanism and principles of system design.The aim of this review is the focus on the peroxidase mimic based colorimetric sensors as the most common nanozyme-based sensors and their classification based on principles of sensor design and review of the detection mechanism of the current mimic peroxidase based sensors.Moreover,some current challenges and future developments in this field are discussed.