Construction And Application Of Colorimetric Sensing System Based On Molybdenum Trioxide

Colorimetric sensing has the advantages of simplicity,high efficiency,high sensitivity and without using complex instruments,which can meet the needs of rapid on-site detection in real environmental monitoring.The introduction of noble metal nanomaterials has effectively perfected the construction methods of colorimetric sensors,improved their analytical performance,and it further has promoted the development of colorimetric sensing technology.This paper introduces the property of local surface plasmon resonance?LSPR?of traditional noble metal nanomaterials and their common construction strategies in colorimetric sensing,and summarizes the current shortcomings of colorimetric sensing methods based on noble metal nanomaterials.Molybdenum trioxide?MoO₃?has been widely used in the fields of sensing,catalysis,energy storage devices and so on due to its excellent chemical and physical properties.As a wide-band gap semiconductor,MoO₃ can be doped.The doped MoO₃ is an alternative material to replace the traditional noble metal and avoid the inherent disadvantages of the traditional nanomaterials.Up to now,the research on reversible local surface plasmon resonance property of molybdenum trioxide and the direct colorimetric sensing method based on the property are still in the initial stage.This paper focuses on the reversible regulation of LSPR of molybdenum trioxide.Three simple,rapid,sensitive and label-free colorimetric sensing platforms are established,and the experiments indicate that they have the potential to monitor water quality in the actual environment.The detail contents are as follows:1.A three-input logic gate?AND-INH?was designed and used for direct visual detection of stannous ion(Sn²⁺)and nitrite?NO₂^-?.MoO₃ nanosheet dispersion were obtained by direct liquid-phase exfoliation,and the blue MoO_3-x nanomaterials with LSPR were prepared by reducing agents(Sn²⁺)under acidic conditions at room temperature.The characterization of MoO₃ and MoO_3-x was carried out by transmission electron microscope,X-ray diffractometer and ultraviolet-visible spectrophotometer.The blue plasma MoO_3-x turns colorless by the introduction of oxidant?NO₂^-?to achieve the reversible regulation of LSPR of MoO₃.Thus,the concatenated logic gate with Sn²⁺,H⁺and NO₂^-as inputs was built and rapid detection of Sn²⁺and NO₂^-was realized.2.A phosphate(PO₄^3-)colorimetric sensor based on the tunable LSPR of MoO₃ was developed.With the introduction of reducing agent of ascorbic acid?AA?,system can generates yellow plasma MoO_3-x.When PO₄^3-is present,it can tune the plasma properties of MoO_3-x to gradually produce blue MoO_3-x.Based on the tunable LSPR of MoO₃ in the process,a label-free colorimetric sensor for the detection of PO₄^3-was established.The effects of reaction conditions?solution pH and reaction components concentration?on the sensing sysytem were investigated,and the experimental parameters were optimized to obtain better sensitivity.Moreover,the detection performance of the system and its ability to detect PO₄^3-in real water samples are also studied.3.A silver ion?Ag⁺?colorimetric sensing platform based on plasma MoO_3-x hot electron transfer mechanism was constructed.The blue plasma MoO_3-x with rich oxygen vacancies was prepared by the reduction of sodium borohydride?NaBH₄?,and its reaction with Ag⁺was obviously promoted by light.The transmission electron microscope,energy spectrum analyzer,and ultraviolet-visible spectrophotometer were used to characterize the solution before and after the reaction.Furthermore,the light color control and the nitrogen saturated contrast experiments were carried out.Based on the above results,the hot electron transfer mechanism of plasma MoO_3-x under white light illumination was proposed.And a label-free Ag⁺colorimetric sensing platform was constructed.The detection performance of this sensing platform was examined and the detection ability in actual environment was evaluated.