NIR-responsive NaYF4:Yb,Er,Gd fluorescent upconversion nanorods for the highly sensitive detection of blood fingerprints

NaYF4:Yb,Er,Gd upconversion nanorods were employed as a promising fluorescent label for the detection of blood fingerprints with high sensitivity, low background, high efficiency and low toxicity on a range of substrates including non-infiltrating materials (glass, ceramic tile, aluminium foil, stainless steel sheet, coin and marble), and infiltrating materials (magazine cover and train ticket).