Method for producing water-insoluble quantum dot patterns

Abstract

The present invention relates to a method for producing water-insoluble quantum dot patterns on and/or within a substrate. The method comprises a step of depositing a deliquescent salt, quantum dots and an acid or salt thereof onto at least one surface region of a substrate such that the deliquescent salt, the quantum dots and the acid or salt thereof are at least partially contacted to form said at least one water-insoluble pattern.

Claims

1. A method for producing a water-insoluble pattern on and/or within a substrate, the method comprising the following steps: (a) providing a substrate; (b) providing a deliquescent salt comprising a cation; (c) providing quantum dots; (d) providing an acid or a salt thereof comprising said anion, wherein the acid is a Brønsted-Lowry acid; and (e) depositing the deliquescent salt provided in step (b), the quantum dots provided in step (c) and the acid or salt thereof provided in step (d) onto at least one surface region of the substrate provided in step (a) wherein the deliquescent salt, the quantum dots and the acid or salt thereof are at least partially contacted to form at least one water-insoluble pattern on said substrate, within said substrate, or both on and within said substrate, wherein (i) the deliquescent salt and the quantum dots are deposited simultaneously or (ii) the deliquescent salt and the quantum dots are deposited consecutively in any order.

2. The method according to claim 1, wherein the deliquescent salt provided in step (b), the quantum dots provided in step (c), the acid or salt thereof provided in step (d), or a combination thereof, is/are provided in the form of a liquid composition.

3. The method according to claim 1, wherein the deliquescent salt provided in step (b) and the quantum dots provided in step (c) are provided together in one single liquid composition, wherein the deliquescent salt and the quantum dots are deposited simultaneously.

4. The method according to claim 1, wherein the substrate is a planar substrate having a first side and a reverse side, and (i) the deliquescent salt provided in step (b), the quantum dots provided in step (c) and the acid or salt thereof provided in step (d) are deposited onto said first side of the substrate, or (ii) the deliquescent salt provided in step (b), the quantum dots provided in step (c) and the acid or salt thereof provided in step (d) are deposited onto said reverse side of the substrate.

5. The method according to claim 1, wherein the substrate is a planar substrate having a first side and a reverse side, and (i) the deliquescent salt provided in step (b) and the quantum dots provided in step (c) are deposited onto said first side of the substrate and the acid provided in step (d) is deposited onto said reverse side of the substrate, or (ii) the acid or salt thereof provided in step (d) is deposited onto said first side of the substrate and the deliquescent salt provided in step (b) and the quantum dots provided in step (c) are deposited onto said reverse side of the substrate.

6. The method according to claim 1, wherein the method further comprises a step of drying the substrate after depositing the deliquescent salt provided in step (b), after depositing the quantum dots provided in step (c), after depositing the acid or salt thereof provided in step (d)), or a combination thereof.

7. The method according to claim 1, wherein the deliquescent salt is selected from the group consisting of chlorates, sulphates, halides, nitrates, carboxylates, chlorides, bromides, iodides, citrates, acetates, zinc iodide, manganese chloride, calcium chlorate, cobalt iodide, copper chlorate, manganese sulphate, stannic sulphate, magnesium chloride, calcium chloride, iron chloride, copper chloride, zinc chloride, aluminium chloride, magnesium bromide, calcium bromide, iron bromide, copper bromide, zinc bromide, aluminium bromide, magnesium iodide, calcium iodide, magnesium nitrate, calcium nitrate, iron nitrate, copper nitrate, silver nitrate, zinc nitrate, aluminium nitrate, magnesium acetate, calcium acetate, iron acetate, copper acetate, zinc acetate, aluminium acetate, and mixtures and hydrates thereof.

8. The method according to claim 1, wherein the quantum dots are selected from: (i) metal-based quantum dots; (ii) CdTe quantum dots; (iii) carbon quantum dots; (iv) peptide-based quantum dots; and mixtures of any of the foregoing.

9. The method according to claim 1, wherein the acid is selected from the group consisting of hydrochloric acid, sulphuric acid, sulphurous acid, phosphoric acid, oxalic acid, tartaric acid, carbonic acid and mixtures thereof.

10. The method according to claim 2, wherein: (i) the deliquescent salt is present in the liquid composition in an amount of from 0.1 to 100 wt %, based on the total weight of the liquid composition; (ii) the quantum dots are present in the liquid composition in an amount of from 0.0001 to 20 wt %, based on the total weight of the liquid composition; (iii) the acid or salt thereof is present in the liquid composition in an amount of from 0.1 to 100 wt %, based on the total weight of the liquid composition; or (iv) a combination thereof.

11. The method according to claim 1, wherein the deliquescent salt is calcium chloride, the quantum dots are CdTe quantum dots, and the acid is phosphoric acid.

12. The method according to claim 1, wherein the substrate is selected from the group consisting of paper, cardboard, containerboard, plastic, cellophane, textile, wood, metal, glass, mica plate, cellulose, nitrocellulose, cotton, marble, calcite, natural stone, composite stone, brick, concrete, tablet, canvas, natural materials of human or animal origin, and laminates or composites thereof.

13. The method according to claim 1, wherein the deliquescent salt provided in step (b), the quantum dots provided in step (c) and/or the acid or salt thereof provided in step (d) is/are deposited by electronic syringe dispensing, spray coating, inkjet printing, offset printing, flexographic printing, screen printing, plotting, contact stamping, rotogravure printing, powder coating, spin coating, reverse gravure coating, slot coating, curtain coating, slide bed coating, film press, metered film press, blade coating, brush coating, a pencil, or a combination thereof.

14. The method according to claim 1, wherein the water-insoluble pattern is a channel, a barrier, a one-dimensional bar code, a two-dimensional bar code, a three-dimensional bar code, a security mark, a number, a letter, an alphanumerical symbol, a text, a logo, an image, a braille marking, a shape, a design, or a combination thereof.

15. The method of claim 1, wherein the deliquescent salt, the quantum dots, or both are deposited before depositing the acid or salt thereof.

16. The method of claim 2, wherein the deliquescent salt provided in step (b), the quantum dots provided in step (c) and the acid or salt thereof provided in step (d) are provided in the form of a liquid composition.

17. The method of claim 2, wherein the deliquescent salt provided in step (b), the quantum dots provided in step (c) and the acid or salt thereof provided in step (d) are provided in the form of an aqueous composition.

18. The method of claim 1, wherein the deliquescent salt and the acid or salt thereof are selected so that the cation of the deliquescent salt and the anion of the acid or salt thereof form a water-insoluble salt.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a treated substrate with the inventive water-insoluble pattern under ambient light from a top view (about 90°).

(2) FIG. 2 shows the same treated substrate with the inventive water-insoluble pattern under UV light (365 nm).

(3) FIG. 3 shows a treated substrate with the inventive water-insoluble pattern under ambient light from a top view (about 90°).

(4) FIG. 4 shows the same treated substrate with the inventive water-insoluble pattern under UV light (365 nm).

EXAMPLES

(5) The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention.

(A) Analytical Methods

(6) Digital Photographs and Illumination

(7) Images of prepared samples were recorded with an EOS 600D digital camera equipped with a Canon Macro lens, EF-S 60 mm, 1:2.8 USM (Canon Japan).

(8) For illumination under ambient light conditions, a RB 5055 HF Lighting Unit (Kaiser Fototechnik GmbH & Co. KG, Germany) was used. The prepared samples were placed in the centre of the mid table of the lighting unit and were illuminated with one of the two lamps, wherein the distance between the substrates and the centre of the lamp was about 50 cm. For illumination under UV light, a handheld UV light MR 96 B Minilight (MR Chemie GmbH, Germany) having a peak wavelength at 365 nm was used.

(9) Energy-Dispersive X-Ray (EDS) Analysis

(10) The prepared samples were examined by a Sigma VP field emission scanning electron microscope (Carl Zeiss AG, Germany) The backscattered electron images were recorded in COMPO-Mode with a chamber pressure of about 50 Pa in order to visualize differences in the chemical composition of the sample. The heavier the atomic weight of the elements present, the brighter the particle appears in the image.

(11) The energy-dispersive X-ray images were recorded with an Oxford X-Max SDD-detector (Silicon Drift Detector) 50 mm.sup.2 (Oxford Instruments PLC, United Kingdom) and chamber pressure about 40-90 Pa (40-60 Pa for surfaces/approx. 90 Pa for cross-sections). Dot-mappings and EDS-analysis were taken with the energy dispersive x-ray detector (EDS). The EDS-detector determines the chemical elements of a sample and can show the position of the elements in the sample.

(B) Examples

(12) The following example is not to be construed to limit the scope of the claims in any manner whatsoever.

(13) Materials

(14) Substrate

(15) A commercial paper type “ANTIK” from Security Paper Mill (SPM), Praha, Czech Republic was used. It is a pulp-based, surface-seized slightly yellowish art paper having a basis weight of 130 g/m.sup.2.

(16) Ink Composition A: Deliquescent Salt and Quantum Dots

(17) An aqueous ink composition containing 35 wt % calcium chloride, 10 wt % ethanol, and 55 wt % water was prepared.

(18) 8 g of the above calcium chloride ink composition were mixed with 0.005 g of CdTe core-type quantum dots functionalized with COOH function (#777951-25MG from Sigma-Aldrich).

(19) Ink Composition B: Deliquescent Salt and Quantum Dots

(20) An aqueous ink composition containing 35 wt % calcium chloride, 10 wt % ethanol, and 55 wt % water was prepared.

(21) 7.9 g of the above calcium chloride ink composition were mixed with 2.4 g of blue luminescent graphene quantum dots (BGQDs) prepared in water solvent (item number: 06-0336, 100 mL, CAS 7735-18-5, LOT No. 21418300 from Strem Chemicals, Inc.)

(22) Ink Composition C: Acid

(23) An aqueous ink composition containing 40 wt % phosphoric acid, 24 wt % ethanol, and 36 wt % water was prepared.

(24) Preparation of Patterned Substrate and Results

(25) An inkjet printer (Dimatix DMP 2831, Fujifilm Dimatix Inc., USA) with 10 μl droplet size at a drop spacing of 30 μm was used.

Example 1

(26) The substrate was inkjet printed in form of a pre-defined pattern first with ink composition A (deliquescent salt and CdTe quantum dots) described above. After 15 min, ink composition C (acid) was then inkjet printed onto the same substrate in form of the same pattern and at the same position.

(27) The formed water-insoluble pattern was hardly visible to the naked eye from a top view (about 90°) on the substrate under ambient light conditions (see FIG. 1). The elements of the quantum dots (Cd, Te) were not detectable by EDS. However, the printed pattern became visible (red, fluorescence) under UV light at 365 nm (see FIG. 2).

Example 2

(28) The substrate was inkjet printed in form of a pre-defined pattern first with ink composition B (deliquescent salt and graphene quantum dots) described above. After 15 min, ink composition C (acid) was then inkjet printed onto the same substrate in form of the same pattern and at the same position.

(29) The formed water-insoluble pattern was hardly visible to the naked eye from a top view (about 90°) on the substrate under ambient light conditions (see FIG. 3). The printed pattern became visible (blue, fluorescence) under UV light at 365 nm (see FIG. 4).