A dye mixture comprising at least one dye of formula

##STR00001##

and at least one dye from the group of formulae

##STR00002##

wherein
(R.sub.1).sub.k denotes k identical or different substituents from the group C.sub.1-C.sub.4alkoxy, C.sub.1-C.sub.4alkyl and sulfo,
R.sub.2 is hydrogen or C.sub.1-C.sub.4alkyl,
R.sub.3 is hydrogen or C.sub.1-C.sub.4alkyl,
(R.sub.4).sub.n denotes n identical or different substituents from the group C.sub.1-C.sub.4alkoxy, C.sub.1-C.sub.4alkyl and sulfo,
(R.sub.5).sub.q denotes q identical or different substituents from the group C.sub.1-C.sub.4alkoxy and C.sub.1-C.sub.4alkyl,
X.sub.1, X.sub.2 and X.sub.3 are each independently of the others halogen, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl,
T.sub.1 is a fibre-reactive radical of formula

##STR00003##

wherein
(R.sub.6).sub.0-2 denotes from 0 to 2 identical or different substituents from the group C.sub.1-C.sub.4alkyl, C.sub.1-C.sub.4alkoxy and sulfo,
Me means methyl, and Et means ethyl,
Z, Z.sub.1, Z.sub.2 and Z.sub.3 are each independently of the others vinyl or a radical CH.sub.2CH.sub.2U and U is a group removable under alkaline conditions,
M is hydrogen, an alkali metal or one equivalent of an alkaline earth metal,
k, n and q are each independently of the others the number 0, 1 or 2, and
l, m and s are each independently of the others the number 1 or 2,
are suitable especially for the dyeing or printing of cellulosic fibre materials, exhibit good build-up, and yield dyeings and prints having good reproducibility and good all-round fastness properties.

The present invention relates to novel bisazo dyes, a process for their preparation and their use for dyeing and/or printing substrates.

Fluorescence titration of methylene blue, rhodamine B and rhodamine 6G (R6G) by silver nanoparticle (AgNP) all resulted in an initial steep quenching curve followed with a sharp turn and a much flatter quenching curve. At the turn, there are about 200,000 dye molecules per a single AgNP, signifying self-assembly of approximately 36 layers of dye molecules on the surface of the AgNP to form a micelle-like structure. These fluorescence-quenching curves fit to a mathematical model with an exponential term due to molecular self-assembly on a AgNP surface, or self-assembly shielding effect, and a Stern-Volmer term (nanoparticle surface enhanced quenching). Such a super-quenching by AgNP can only be attributed to pre-concentration of the dye molecules on the nanoparticle surface that yields the formation of micelle-like self-assembly, resulting in great fluorescence quenching. Overall, the fluorescence quenching titration reveals three different types of interactions of dye molecules on AgNP surface: 1) self-assembly (methylene blue, rhodamine B and R6G), 2) absorption/tight interaction (tryptamine and fluorescein), and 3) loose interaction (eosin Y). We attribute the formation of micelle-like self-assembly of these three dye molecules on AgNP to their positive charge, possession of nitrogen atoms, and with relatively large and flat aromatic moieties.

Fluorescence titration of methylene blue, rhodamine B and rhodamine 6G (R6G) by silver nanoparticle (AgNP) all resulted in an initial steep quenching curve followed with a sharp turn and a much flatter quenching curve. At the turn, there are about 200,000 dye molecules per a single AgNP, signifying self-assembly of approximately 36 layers of dye molecules on the surface of the AgNP to form a micelle-like structure. These fluorescence-quenching curves fit to a mathematical model with an exponential term due to molecular self-assembly on a AgNP surface, or self-assembly shielding effect, and a Stern-Volmer term (nanoparticle surface enhanced quenching). Such a super-quenching by AgNP can only be attributed to pre-concentration of the dye molecules on the nanoparticle surface that yields the formation of micelle-like self-assembly, resulting in great fluorescence quenching. Overall, the fluorescence quenching titration reveals three different types of interactions of dye molecules on AgNP surface: 1) self-assembly (methylene blue, rhodamine B and R6G), 2) absorption/tight interaction (tryptamine and fluorescein), and 3) loose interaction (eosin Y). We attribute the formation of micelle-like self-assembly of these three dye molecules on AgNP to their positive charge, possession of nitrogen atoms, and with relatively large and flat aromatic moieties.

Described are contact lenses that contain high energy visible (HEV) light absorbing compounds and their use for improving one or more vision attributes.

Described are contact lenses that contain high energy visible (HEV) light absorbing compounds and their use for improving one or more vision attributes.