ISBN : 978-602-17761-4-8
52
Proceedings of 2
nd
REPTech Crowne Plaza Hotel, Bandung, November 15-17, 2016
© 2016 Published by Center for Pulp and Paper through 2
nd
REPTech
Therefore, the development of a high-performance, user-friendly method to detect heavy metal ions, such as Cu
2+
, in water is in strong demand, and would allow nonprofessionals to determine water safety, especially in Third World countries. Herein, we proposed and developed a simple low-cost method,
using inkjet printing technology to fabricate a paper-based copper ion sensor for both qualitative and quantitative detection. A commercial anthraquinone dye and common ilter paper were used as the
main chemical and substrate, respectively, for sensor fabrication. Consequently, the developed paper- based sensor can realize both qualitative detection of Cu
2+
in water and quantitative detection based on luorescence spectroscopy for high ion species selectivity and sensitivity.
Experimental 2.1 Materials
An anthraquinone derivative Sigma-Aldrich and ilter paper No. 1, Advantec were used as the sensing dye and substrate of the sensor, respectively. Metal nitrate salts, including sodium, potassium,
calcium, ferric, cobalt, cadmium, manganese, mercury, lead, nickel, zinc, and silver nitrates Japanese Industrial Standard [JIS] special grade, Wako Pure Chemical, were used in the experiment to evaluate
interference by metal ions other than Cu
2+
. Copper standard solution Cu 100, Wako Pure Chemical was used to calibrate Cu
2+
concentrations measured by ICP–OES Optima-7300DV, PerkinElmer, USA and the paper-based sensor.
2.2 Fabrication
A lab-made ink, comprising a 1 gL anthraquinone derivative acetone solution, was irst prepared. An inkjet printer DMP-2831, Dimatix, Fujiilm, Japan was then used to fabricate the paper-based
sensor by printing this ink onto ilter paper. The designed printing pattern was a rectangle with a 30-mm length and 20-mm width, which was the most appropriate size for the sample holder in luorescence
spectroscopy in luorescence detection. The ink dried in 10 s after printing, and the anthraquinone derivative was adsorbed onto the cellulose ibers through non-covalent interactions. Filter paper printed
with the rectangular pattern is denoted as the “paper-based sensor” throughout. The paper-based sensors were cut out from the ilter paper for further use.
2.3 Characterization
In the experiment, a confocal laser scanning microscope CLSM LSM-700, Carl Zeiss, Germany was used to observe the distribution of the anthraquinone derivative on iber surfaces and in iber
networks. The ilter paper was irst stained with a 0.01 gmL Nile blue–acetone solution by pipetting. After drying, a 0.5 gL anthraquinone derivative acetone solution was printed onto the stained ilter paper
using the Dimatix inkjet printer. A paper sample with a 45° beveled cross-section was then prepared by cutting paper sandwiched between polystyrene blocks with a 45° beveled plane using a razor blade. The
prepared paper sample was then pasted onto a glass slide and observed using CLSM. Double-track mode was applied to the laser scan. In one laser scanning track, the Ar laser at 488 nm was selected to excite
and detect anthraquinone derivative, while in the other track, the He–Ne laser at 634 nm was selected
to excite Nile blue in order to reveal the whole iber network. The scanning depth was 200 μm, which was approximately equal to the ilter paper thickness. Finally, 3D images of the paper-based sensor were
captured.
2.4 Visible and Fluorescence Detections
In the visible detection, also referred to as qualitative detection, the paper-based sensors fabricated using 0.6 gL anthraquinone derivative acetone solution were immersed in 5-mL Cu
2+
aqueous solutions with concentrations of 1, 2, 3, 4, and 5 ppm for 10 min. After immersion, the sensor color was observed
by the naked eye and captured using a digital camera.
ISBN : 978-602-17761-4-8
53
Proceedings of 2
nd
REPTech Crowne Plaza Hotel, Bandung, November 15-17, 2016
© 2016 Published by Center for Pulp and Paper through 2
nd
REPTech
In the luorescence detection, also referred to as quantitative detection by applying luorescence spectroscopy F-4500, Hitachi, Japan, the surface luorescence intensity of the paper-based sensor
was measured. The excitation and emission wavelengths were 490 nm and 567 nm, respectively. As anthraquinone derivative was quenched by Cu
2+
in solution, the surface luorescence intensity of paper- based sensors immersed in Cu
2+
solutions of various concentrations was determined. Paper-based sensors, fabricated using a 1 gL anthraquinone derivative acetone solution, were
immersed in 5-mL Cu
2+
solutions with concentrations of 1, 2, 3, 4, 5, and 6 ppm for 10 min. Additionally, to achieve higher sensitivity, paper-based sensors were fabricated using an anthraquinone derivative
acetone solution of lower concentration 0.4 gL. Subsequently, these fabricated sensors were immersed in 5-mL Cu
2+
solutions with concentrations of 200, 400, 600, and 800 ppb for 10 min. After immersion, excess water was removed with a paper wiper. Before drying, the surface luorescence intensity of the
paper-based sensors was measured, and the relationship between surface luorescence intensity and Cu
2+
concentration was determined. All aqueous samples in this research were adjusted to pH 7 using a buffer solution containing
4-2-hydroxyethyl-1-piperazineethanesulfonic acid HEPES and NaOH, which is widely used in research related to heavy metal solutions.
2.5 Interference
