Red and green are two of the most‐preferred colors from the entire chromatic spectrum, and red and green dyes are widely used in biochemistry, immunohistochemistry, immune‐staining, and nanochemistry applications. Selective dyes with green and red excitable chromophores can be used in biological environments, such as tissues and cells, and can be irradiated with visible light without cell damage. This critical review, covering a period of five years, provides an overview of the most‐relevant results on the use of red and green fluorescent dyes in the fields of bio‐, chemo‐ and nanoscience. The review focuses on fluorescent dyes containing chromophores such as fluorescein, rhodamine, cyanine, boron–dipyrromethene (BODIPY), 7‐nitobenz‐2‐oxa‐1,3‐diazole‐4‐yl, naphthalimide, acridine orange, perylene diimides, coumarins, rosamine, Nile red, naphthalene diimide, distyrylpyridinium, benzophosphole P‐oxide, benzoresorufins, and tetrapyrrolic macrocycles. Metal complexes and nanomaterials with these dyes are also discussed.

In this work, the successful preparation and characterization of gold nanorods (AuNRs) coated with a mesoporous silica shell (AuNRs@Simes) was achieved. Conjugation with methylene blue (MB) as a model drug using ultrasound-stimulated loading has been explored for further application in light-mediated antibacterial studies. Lyophilization of this conjugated nanosystem was analyzed using trehalose (TRH) as a cryogenic protector. The obtained stable dry formulation shows potent antimicrobial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria after a simple post-treatment irradiation method with a red laser during a short time period.