Abstract:
A potentiometric Mg 2+  sensor is disclosed, wherein the potentiometric SnO 2 /ITO-based Mg 2+  ISE was developed in this invention. The magnesium ion-selective membrane was fabricated and dripped on the surface of SnO 2 . The performance, such as sensitivity, was exhibited by the magnesium ion-selective membrane having magnesium ionophore, K-TpClPB, plasticizer, PVC in the suitable ratios. Moreover, the Mg 2+  ISE was measured in different Mg 2+  concentration buffer solutions. According to the experimental results, the best sensitivity of the Mg 2+  sensor is 31.7l mV/decade between 10-4M and 10-1M, and measurement time is 30 sec.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to magnesium ion sensor and fabrication method, and more particularly to potentiometric magnesium ion sensor and fabrication method. 
         [0003]    2. Description of the Prior Art 
         [0004]    For hygiene, the concentration of Mg2+ is one of the most important parameter in the clinical assay, the Mg2+ activity in blood serum was shown to decrease during liver transplantation due to accumulation of citrate and concomitant chelation of Mg2+. A low Mg2+ activity has been observed in patients suffering from acute migraine, headaches and cardiac diseases. The disadvantage of traditional potentiometric Mg 2+  devices are expensive and hard to fabricate. In order to make the measurement of magnesium ion easily, magnesium ISEs (Ion-selective electrode) have been developed in this invention. 
       SUMMARY OF THE INVENTION 
       [0005]    Therefore, in accordance with the previous summary, objects, features and advantages of the present disclosure will become apparent to one skilled in the art from the subsequent description and the appended claims taken in conjunction with the accompanying drawings. 
         [0006]    A potentiometric magnesium ion sensor and fabrication method is disclosed. At first, a conduction layer is formed on a substrate. Then, a SnO 2  thin-film is deposited on the conduction layer by radio frequency sputtering method, and the conduction layer, the SnO 2  thin-film and a conducting line are connected by a conduction paste. Thereupon, an insulation layer is formed, wherein the conduction layer, the SnO 2  thin-film and one end of the conducting line are coated with the insulation layer, and an opening of the insulation layer is formed on the SnO 2  thin-film. Finally, a magnesium ion-selective membrane is formed by dropping the material of the magnesium ion-selective membrane on the opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the disclosure. In the drawings: 
           [0008]      FIG. 1  is a diagram illustrates the fabrication and structural diagram of a potentiometric magnesium ion sensor; 
           [0009]      FIG. 2  is a diagram depicts the operations of a potentiometric magnesium ion system; and 
           [0010]      FIG. 3 ,  FIG. 4 ,  FIG. 5  and  FIG. 6  are diagrams show the experimental data. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0011]    The present disclosure can be described by the embodiments given below. It is understood, however, that the embodiments below are not necessarily limitations to the present disclosure, but are used to a typical implementation of the invention. 
         [0012]    Having summarized various aspects of the present invention, reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein. On the contrary the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims. 
         [0013]    It is noted that the drawings presents herein have been provided to illustrate certain features and aspects of embodiments of the invention. It will be appreciated from the description provided herein that a variety of alternative embodiments and implementations may be realized, consistent with the scope and spirit of the present invention. 
         [0014]    It is also noted that the drawings presents herein are not consistent with the same scale. Some scales of some components are not proportional to the scales of other components in order to provide comprehensive descriptions and emphasizes to this present invention. 
         [0015]    Please refer to  FIG. 1 , which is a fabrication and structural diagram of a potentiometric magnesium ion sensor  100 . At first, a conduction layer  120  is formed on a substrate  110 . Then, a SnO 2  thin-film  130  is deposited on the conduction layer  120  by radio frequency sputtering method, and the conduction layer  120 , the SnO 2  thin-film  130  and a conducting line  140  are connected by a conduction paste. Thereupon, an insulation layer  150  is formed, wherein the conduction layer  120 , the SnO 2  thin-film  130  and one end of the conducting line  140  are coated with the insulation layer  150 , and an opening of the insulation layer  150  is formed on the SnO 2  thin-film  130 . Finally, a magnesium ion-selective membrane  160  is formed by dropping the material of the magnesium ion-selective membrane  160  on the opening. 
         [0016]    The substrate  110  could comprise glass, and the conduction layer  120  could comprise Indium Tin Oxide (ITO). The insulation layer  150  could comprise Epoxy, and the conduction paste could comprise silver paste. The magnesium ion-selective membrane  160  consists of magnesium ionophore, K-TpClPB, plasticizer, and Poly (vinyl choride). Moreover, the performance was exhibited by the magnesium ion-selective membrane having magnesium ionophore:K-TpClPB: plasticizer:Poly(vinyl choride) in the weight ratio (wt %) 1.40:1.00:64.50:33.10. 
         [0017]    However, the  FIG. 1  also shows the structure of the potentiometric magnesium ion sensor  100 , comprising the substrate  110 , the conduction layer  120 , the SnO 2  thin-film  130 , the conducting line  140 , the insulation layer  150  and the magnesium ion-selective membrane  160 . The conduction layer  120  is formed on the substrate  110 , and the SnO 2  thin-film  130  is formed on the conduction layer  120 . The conduction layer  120  and the SnO 2  thin-film  130  is coated with the insulation layer  150 , and an opening of the insulation layer  150  is formed above the SnO 2  thin-film  130 . The magnesium ion-selective membrane  160  is formed on the opening, wherein the magnesium ion-selective membrane  160  is for magnesium ions passing, and redox reaction would be made between magnesium ions and the SnO 2  thin-film  130 . 
         [0018]    Also as noted above, the potentiometric magnesium ion sensor  100  further includes the above-mentioned conducting line  140 , wherein one end of the conducting line  140  is connected to the conduction layer  120  and the SnO 2  thin-film  130 , and the conduction layer  120 , the SnO 2  thin-film  130  and the conducting line  140  could by the conduction paste, which could be silver paste. 
         [0019]    The potentiometric magnesium ion system  170  is shown in  FIG. 2 . As shown in the  FIG. 2 , the potentiometric magnesium ion system  170  comprises the potentiometric magnesium ion sensor  100 , a reference electrode  172 , an amplifier (LT1167)  174 , a digital multi-meter  176 , and a computer  178 . 
         [0020]    The amplifier is electronically coupled with the conduction layer  120  by the conducting line  140 , wherein one end of the conducting line  140  is connected to the conduction layer  120  and the SnO 2  thin-film  130 , and the other end of the conducting line  140  is connected with the amplifier  174  by passing through the insulation layer  150 . Moreover, the digital multi-meter  176  is electronically coupled with the amplifier  174 , and measures the output signals from the amplifier  174  to output measurement values. Then, the computer  178  is electronically coupled with the digital multi-meter  176  for computing the measurement values from the digital multi-meter  176 . 
         [0021]    The potentiometric magnesium ion sensor  100  and the reference electrode  172  are immersed into a butter solution  180 , and the reference electrode  172  is held out at a reference potential. When magnesium ions pass through the magnesium ion-selective membrane  160  to react with the SnO 2  thin-film  130 , the potentiometric magnesium ion sensor  100  would output a signal according to a potential difference between the potentiometric magnesium ion sensor  100  and the reference electrode  172 . 
         [0022]    The signal from the potentiometric magnesium ion sensor  100  is immediately transmitted to the digital multi-meter  176  and the computer  178  by the amplifier  174 , and the concentration of the magnesium ions in the buffer solution  180  is measured and analyzed by the digital multi-meter  176  and the computer  178 . 
         [0023]    According to the experimental results, the sensitivity of the potentiometric magnesium ion sensor  100  is about 31.71 mV/decade when the concentration range of the magnesium ions is between 1×10-4 M and 0.1 M, and measurement time is about 30 seconds. Besides, the relations between the concentration of the magnesium ions and the potential are shown in  FIG. 3  and  FIG. 4 , and the reaction curve of the potentiometric magnesium ion sensor  100  is shown in  FIG. 5 , wherein the reaction time is less than 1 second. In addition, the best sensitivity of the potentiometric magnesium ion sensor  100  is about 31.71 mV/decade when the concentration range of the magnesium ions in the buffer solution  180  is between 1×10-4 M and 0.1 M, as shown in  FIG. 6 . 
         [0024]    The foregoing description is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. In this regard, the embodiment or embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the inventions as determined by the appended claims when interpreted in accordance with the breath to which they are fairly and legally entitled. 
         [0025]    It is understood that several modifications, changes, and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.