Patent Application
20240125736
This application claims the priority of Taiwanese patent application No. 111139497, filed on Oct. 18, 2022, which is incorporated herewith by reference.
The invention relates to a Cu ion sensor and a Cu ion sensing method, in particular to a Cu ion sensor for sensing Cu ions in drinking water.
Heavy metal ions such as arsenic, chromium, copper, lead, mercury, cadmium etc. are toxic above certain contents or concentrations, which causes a threat to human health as well as environments. Therefore, removal of these bio-hazardous elements from aqueous solutions, foods, or body fluids is crucial to life. Detection of these heavy metals with high accuracy is essential prior to the removal process.
Various detection methods have been adopted in past years with respective pros and cons for specific detection of heavy metal ions. Likewise, large efforts have been dedicated to detect copper ions (Cu2+), since it is an essential trace element to life while it becomes deadly over a concentration of 1.3 mg/L.
Several predominant analytical processes such as colorimetry, atomic absorption spectroscopy, inductively coupled plasma atomic emission spectrometry, electrochemical, and optical chemical sensing are generally carried out for detection of Cu2+. Although the above detection methods can reach nano-molar to pico-molar levels, the instruments are complicated to operate, highly specialized, expensive, and difficult to maintain.
Therefore, in the present, there is an urgent need to develop a novel Cu ion sensor, which not only has high sensitivity, low detection limit and low cost, but also can achieve simple process and simple measurement technology.
In view of this, the present invention provides a Cu ion sensor and a Cu ion sensing method.
The Cu ion sensor of the present invention comprises: a substrate; a patterned electrode disposed on the substrate; and a copper nitride film, which is disposed on the patterned electrode and the substrate and doped with a metal material, wherein a nitrogen-rich plane of the copper nitride film increases with an increase in a doping content of the metal material without exceeding a maximum doping content of the metal material.
Specifically, the substrate can be a quartz glass substrate; the patterned electrode can be an indium-tin-oxide (ITO) electrode, and further can be an interdigitated electrode; the copper nitride film can be a Cu3N film; and the metal material can be Ti.
In addition, the present invention provides a Cu ion sensing method comprising the following steps: providing a solution to be tested containing Cu ions; contacting the Cu ion sensor with the solution to be tested; applying a fixed bias to the Cu ion sensor; measuring a current of the solution to be tested; using the current to calculate an electrical conductivity of the solution to be tested; and plotting the electrical conductivity against a Cu ion concentration to obtain a linear relationship to detect the Cu ions.
In addition, as the content of the metal material in the copper nitride film increases, the Cu ion sensor of the present invention has high sensitivity and high response to Cu, so it is suitable for detecting Cu2+ at concentrations in pico-molar to nano-molar levels.
The effects of the present invention are not limited to the above-mentioned effects, and those skilled in the art can clearly understand other non-mentioned effects from the description of the claims.
Those skilled in the art will understand the above and other objects, features and advantages of the present invention more clearly by the description of the exemplary embodiments in detail with reference to the accompanying drawings, wherein:
Advantages and features of the present invention and implementation methods thereof will be more clearly understood according to the embodiments described below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, but can be implemented in various forms.
Referring to
The substrate 1 is, for example, but not limited to, a quartz glass substrate, available from Corning, such as an EAGLE XG® glass substrate.
The patterned electrode 2 is, for example, but not limited to, an indium-tin-oxide (ITO) electrode, available from Sanyo, Japan.
The patterned electrodes 2 further include interdigitated electrodes.
The copper nitride film 3 is doped with a metal material, wherein the copper nitride can be Cu3N, and the metal material can be titanium (Ti).
Copper and titanium targets with high purity (4N) were purchased from Ultimate material technology (UMAT). The Cu target was 3 inch in diameter and 6 mm in thickness. The Ti target was 2 inch in diameter and 6 mm in thickness.
Referring to
The deposition rate of the Cu3N film was monitored at different DC powers. The deposition rate of pure Cu3N film (i.e., the DC power applied to the Ti source was zero) was 0.191 nm/s and decreased monotonically with the increase in the DC power applied to the Ti source.
As the power applied to Ti increases, more Ti atoms are sputtered, resulting in a shortening of the mean free path and an increase in probability of collisions among atoms. Therefore, the atoms lose energy, which is manifested as the lowered deposition rate with the increase in DC power applied to the Ti source. The film deposition rate was reduced to 0.166 nm/s at a DC power of 200 W.
Referring to
The growth composition of the films was studied by electron probe microanalyzer (EPMA) and is shown in
To investigate the crystal nature of these five Ti-doped Cu3N films, XRD (X Ray Diffractometer) analysis is carried out in the present invention. The XRD patterns of all these films are shown in
The XRD data indicates that the (100) plane dominates over other Cu3N planes at a Ti content of 1.6 at %. The (100) and (111) planes of Cu3N lattice suggest the nitrogen-rich and copper-rich surfaces, respectively. When more nitrogen atoms are presented on the surface of Cu3N film, the probability to capture Cu ions by π-π intermolecular interactions between nitrogen atom and Cu ions increases, suggesting higher sensitivity to Cu ions. Therefore, Cu3N film with higher Ti content is supposed to be more sensitive to Cu ions.
It is noted that the full width at half-maximum (FWHM) of the peaks corresponding to the (100) and (200) planes decreases with the increase in Ti content, suggesting that the films with high Ti content have higher crystallinity Therefore, the XRD data suggests the successful fabrication of pure Cu3N film and Ti-doped Cu3N film with high quality.
When applying different concentration of Cu2+, the electrical conductivity of the Ti-doped Cu3N films will change. As depicted in the
As shown in
The efficient sensing at such a low concentration (pico-molar) imparts the proposed Cu ion sensor in the present invention an excellent industrial applicability.
It is intuitive to increase the Ti content to achieve higher response of the proposed sensor. However, as shown in
The XRD data shows that when the Ti content in the Cu3N film is higher than 1.6%, the formation of TiN phase results in gradual decreases of the peak intensities corresponding to the (100) and (200) planes of Cu3N phase. Since the nitrogen-rich planes (100) and (200) of Cu3N are responsible for the Cu2+ sensing, it can be known that 1.6 at % of Ti is the maximum allowed doping amount in the Cu3N film.
These Ti-doped Cu3N films are then applied to fabricate Cu2+ sensor. Ti-doped Cu3N films with a thickness of 200 nm are deposited on patterned ITO on glass substrates. Plan and cross-sectional views and optical images of the Cu ion sensor are schematically presented in
The Cu ion sensor of the present invention can be used to detect the concentration of Cu ions in drinking water and body fluids. The body fluids can be, for example, urine, blood, sweat, and tears.
An embodiment of the present invention further provides a Cu ion sensing method, using the Cu ion sensor described above for measurement, as shown in
In step S10, the solution to be tested containing Cu ions may be drinking water and phosphate buffered saline (PBS) solution. In step S20, the sensitivity of the proposed sensor is measured according to the change in the current-voltage (I-V) characteristics of the two consecutive ITO electrodes in presence or absence of Cu2+ solution on the Cu3N films.
In step S60, the current increases almost linearly with the increase in the Cu2+ concentration ranging from 8 pM to 80 nM. The high concentration of HNO3 in the Cu2+ solution erodes the Cu3N film, severely limiting the maximum concentration as 80 nM. This long dynamic range (80 nM/8 pM=4 orders of magnitude) of Cu ion sensing is highly promising in industrial or medical fields.
To test the selectivity of the proposed Cu ion sensor, solutions of few other metal ions, such as Selenium (Se4+), Cobalt (Co2+), Arsenic (As3+), Zinc (Zn2+), Nickel (Ni2+), and Cadmium (Cd2+) which are found in drinking water in general, are prepared therein.
In
To test the feasibility of the proposed sensor for practical application, Cu ions are applied in the PBS solution and the responses are measured.
The sensor shows a significant response to Cu2+ in the PBS solution containing disodium hydrogen phosphate, sodium chloride, potassium chloride, and potassium dihydrogen phosphate.
In addition, the sensing of Cu ion in practical sample (i.e., tap water with unknown composition) is tested in present embodiment. Cu ions are added in the tap water which has been filtered by reverse-osmosis (RO) to remove bigger particles.
Cu ion concentrations in any chemical solutions (industrial or domestic wastewater) can be measured with the proposed Cu ion sensors provided the compatibility of the solution to be tested matches with the features of the Cu ion sensor. For example, Cu ion concentrations in chemical solutions containing organic solvents or being acidic or basic can be measured if the compatibility of these chemical solutions matches with the features of the Cu ion sensor.
In conclusion, a Cu ion sensor composed of a copper nitride film doped with metal material deposited on a patterned electrode on a substrate has successfully demonstrated that it can reach pico-molar level detection of Cu ions. With the increase in the doping content of the metal materials, the nitrogen-rich (100) plane is more than the copper-rich (111) plane of the copper nitride film, which can improve the highest response of the copper nitride film to Cu ions. Therefore, due to the high sensitivity of the Cu ion sensor of the present invention to Cu, Cu ions in various solutions can be effectively detected.
Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not limited thereto, and therefore, it should be understood that the above-described embodiments are illustrative in all aspects and do not limit the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111139497 | Oct 2022 | TW | national |
