A luminescent solar concentrator (LSC) device is provided. The LSC device has an active layer including a modified luminophore having a polymethine component including a plurality of methine groups (CH).sub.n, where n is an odd integer greater than 1. A hydrogen atom (H) of one of the plurality of methine groups is replaced by one of -AR.sub.1R.sub.2 or -DR.sub.3, where A is selected from nitrogen (N), phosphorus (P), arsenic (As) and antimony (Sb) and D is selected from oxygen (O), sulfur (S), selenium (Se), and tellurium (Te), R.sub.1 and R.sub.2 are independently selected from H, aliphatic groups, and aromatic groups bound to A through a carbon atom, or R.sub.1 and R.sub.2 together form an alicyclic ring containing A, and R.sub.3 is selected from H, aliphatic groups, aromatic groups, and alicyclic groups bound to D through a carbon atom.

Infrared dyes having an infrared absorption maximum above 1130 nm with minor colouration in the visual spectrum. The infrared dyes are especially useful for producing multicolour laser marked security documents having reduced background coloration and enhanced colour gamut.

The application provides fluorescent dyes, which are cyanine dyes that incorporate additional aza moieties in the indolenium heterocycles and/or in the methine chains connecting them. Symmetrical and unsymmetrical chemically reactive azacyanine dyes are described for conjugation, as well as their bioconjugates for in-vitro and in-vivo assays and fluorescence imaging.