2.1.4. Materials for Preparation of Vehicles for Paste Inks

2-(2-Butoxyethoxy)ethyl acetate (special grade), tetraethyleneglycol monomethyl ether (95%), ethyl cellulose 45 (approximately 49% ethoxy), tetrahydrofuran (special grade), hydrochloric acid (special grade), ethyl acetate (special grade), and magnesium sulfate anhydrous (special grade) were purchased from Wako Pure Chemical Industries (Osaka, Japan). (3-Glycidoxypropyl)trimethoxysilane (GPTMS, 99.2%) was purchased from Shin-Etsu Chemical (Tokyo, Japan). Tetrahydrofuran was used after distillation to remove the stabilizer that was present in the purchase solution; the other reagents were used without further purification.

#### *2.2. Preparation of Copper Nitride Nanoparticles*

Copper nitride nanoparticles were prepared in accordance with previous methods [27]. Copper acetate monohydrate (20 mmol) and urea (100 mmol) were mixed with 1-nonanol (400 mL) in a three-neck flask. The atmosphere in the flask was replaced with nitrogen. The solution was heated by microwave irradiation at 190 ◦C for 60 min (ramp, 30 min; hold, 30 min) by using a microwave oven (μReactorEx, Shikoku Keisoku, Kagawa, Japan) equipped with a fiber optic thermometer (Anritsu Keiki, Tokyo, Japan) to obtain a liquid suspension. After the suspension was centrifuged (30,000× *g* for 60 min) and washed with hexane three times, a red-purple powder was obtained.
