Abstract: A process for preparing in situ an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising ester(s) of retinol represented by formula (I), and (ii) adding a solution of gold salts (Au3+) to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with fixed color with gold nanoparticles dispersed therein. An aqueous gel ink with fixed color obtained according to the process of the invention, comprising the ester of retinol represented by formula (I) and gold nanoparticles. A writing instrument comprising an aqueous gel ink with fixed color.

Abstract: There is a process for preparing in situ an aqueous gel ink with variable color having the following steps: (i) preparing a gel-based matrix of aqueous ink comprising a reducing agent, (ii) adding a solution of metallic salts, (iii) adding iron powder to obtain an aqueous gel ink with variable color, wherein the steps (ii) and (iii) can be interchanged. There also is an aqueous gel ink with variable color obtained according to the process of the disclosure, having a reducing agent, metallic nanoparticles and iron powder. There further is a writing instrument having an aqueous gel ink with variable color according to the disclosure.

Abstract: A process for preparing in situ an aqueous gel ink with variable color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising an N-Acyl-aminophenol, wherein the hydroxyl group is preferably in meta or para position on the benzenic group, and (ii) adding a solution of silver salts to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with variable color with silver nanoparticles disposed therein. An aqueous gel ink with variable color obtained according to process for preparing, comprising an N-Acyl-aminophenol, wherein the hydroxyl group is preferably in meta or para position on the benzenic group and silver nanoparticles. A writing instrument comprising an aqueous gel ink with variable color.

Abstract: The present invention concerns a process for preparing in situ an aqueous gel ink with variable color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising an N-Acyl-aminophenol, wherein said hydroxyl group is preferably in meta or in para position on the benzenic group, and (ii) adding a solution of silver salts to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with variable color with silver nanoparticles dispersed therein. The present invention also relates to an aqueous gel ink with variable color obtained according to the process of the invention, comprising an N-Acyl-aminophenol, wherein said hydroxyl group is preferably in meta or in para position on the benzenic group and silver nanoparticles. The invention finally concerns a writing instrument comprising an aqueous gel ink with variable color according to the invention.

Abstract: The present invention concerns a process for preparing an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink; (ii) preparing an aqueous suspension of silver nanoparticles with fixed color by mixing silver salts with: water, a mixture of at least an alkali metal or alkaline earth metal salt of citrate, preferably an alkali citrate salt and an alkali metal hydride, preferably NaBH4, a further reducing agent, preferably ascorbic acid, and oxidizing agent, preferably hydrogen peroxide H2O2 (iii) adding under agitation the aqueous suspension of silver nanoparticles obtained in step (ii) to the gel-based matrix of aqueous ink obtained in step (i), to obtain an aqueous gel ink with fixed color with silver nanoparticles dispersed therein

Abstract: The present invention concerns a process for preparing in situ an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising ester(s) of retinol represented by formula (I), and (ii) adding a solution of gold salts (Au3+) to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with fixed color with gold nanoparticles dispersed therein. The present invention also relates to an aqueous gel ink with fixed color obtained according to the process of the invention, comprising said ester of retinol represented by formula (I) and gold nanoparticles. The invention finally concerns a writing instrument comprising an aqueous gel ink with fixed color according to the invention.

Abstract: The present invention concerns a process for preparing an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink; (ii) preparing an aqueous suspension of silver nanoparticles with a fixed color by mixing silver salts with: —water, —a mixture of at least an alkali metal or alkaline earth metal salt of citrate, —an oxidizing agent, preferably hydrogen peroxide H2O2, —and polyvinylpyrrolidone; (iii) adding under agitation the aqueous suspension of silver nanoparticles obtained in step (ii) to the gel-based matrix of aqueous ink obtained in step (i), to obtain an aqueous gel ink with fixed color with silver nanoparticles dispersed therein.

Abstract: The invention relates a process for preparing an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink; (ii) preparing an aqueous suspension of gold or silver nanoparticles with a fixed color; (iii) adding the aqueous suspension of gold or silver nanoparticles obtained in step (ii) to the gel-based matrix of aqueous ink obtained in step (i).

Abstract: The present invention concerns a process for preparing in situ an aqueous gel ink with fixed color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising reducing agent chosen in the group consisting of citric acid and/or derivatives of citric acid, (ii) adding a solution of gold salts, (iii) adding iron powder, (iv) adding polyvinylpyrrolidone to obtain an aqueous gel ink with fixed color, wherein the steps (ii) and (iii) can be interchanged. The present invention also relates to an aqueous gel ink with fixed color obtained according to the process of the invention, comprising citric acid and derivatives, gold nanoparticles, and iron powder. The invention finally concerns a writing instrument comprising an aqueous gel ink with fixed color according to the invention.

Abstract: The present invention concerns a process for preparing in situ an aqueous gel ink with variable color comprising the following steps: (i) preparing a gel-based matrix of aqueous ink comprising 0.005 to 0.1 mol·L?1 of ester(s) of retinol represented by formula (I), and (ii) adding a solution of 0.002 to 0.05 mol·L?1 silver salts (Ag+) to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with variable color with silver nanoparticles dispersed therein. The present invention also relates to an aqueous gel ink with variable color obtained according to the process of the invention, comprising said ester of retinol represented by formula (I) and silver nanoparticles.

Abstract: There is a process for preparing in situ an aqueous gel ink with variable color having the following steps: (i) preparing a gel-based matrix of aqueous ink comprising a reducing agent, (ii) adding a solution of metallic salts, (iii) adding iron powder to obtain an aqueous gel ink with variable color, wherein the steps (ii) and (iii) can be interchanged. There also is an aqueous gel ink with variable color obtained according to the process of the disclosure, having a reducing agent, metallic nanoparticles and iron powder. There further is a writing instrument having an aqueous gel ink with variable color according to the disclosure.

Abstract: There is a process for preparing in situ an aqueous gel ink with fixed color having the following steps: (i) preparing a gel-based matrix of aqueous ink comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid as reducing agent, and (ii) adding a solution of metallic salts to the gel-based matrix of aqueous ink prepared in step (i), to obtain an aqueous gel ink with fixed color with metallic nanoparticles dispersed therein. There is also an aqueous gel ink with fixed color obtained according to the process of the disclosure, comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and metallic nanoparticles. There is also a writing instrument comprising an aqueous gel ink with fixed color according to the disclosure.