Luminescent AlN:Mn nanoparticles for optical imaging of biological materials

Abstract

Background: Elaboration of new luminescent nanomaterials for imaging of biological materials including cells of living organisms and their parts is highly actual. These materials must meet a number of requirements such as low toxicity, inherence of intensive luminescence, low costs of raw material and symple synthesis methods. AlN nanopowder is one of such prospective materials fitting the above requirements. Our long time investigations on spectral characteristics for III group element nitrides allows chose of doped AlN nanopowder as prospective candidate for developing of luminescent markers for imaging of biological materials. Objectives: The aim of the present study is spectral characterization of AlN nanopowder doped with Mn and evaluation of its use as luminescent marker for biological materials. Materials and methods: AlN nanopowder with average size of polycrystalline grains of 60 nm and the same doped with Mn were sythesized in Institue of Inorganic Chemistry, Riga Technical University. Photoluminescence and its excitation spectra of the materials were studied at room temperature using a self-made set-up. Results: It was found that in undoped AlN nanopowder at room temperature luminescence of native defects forms a wide and complex band peaking at 415 nm. This blue luminescence can be excited with ultraviolet light from two spectral regions around 315–340 nm and 260 nm. Two luminescence mechanisms are proposed dependent on the spectral region of exciting light. The first of them results in the intra-center luminescence, but the second one is recombination luminescence. Incorporation of Mn atoms in the crystalline lattice of AlN nanopowder forming AlN:Mn NP results in appearance of intensive red luminescence at 600 nm, which can be excited with light from two excitation bands at 260 and 480 nm. Two mechanisms responsible for an appearence of the red luminescence of Mn are proposed. They are the intra-center luminescence and recombination luminescence mechanisms. In this case the red Mn luminiscence prevails and the blue luminescence characterizing the host material has not been observed. Conclusion: AlN nanopowder doped with Mn atoms is a prospective material for use as luminescent marker for imaging of biological materials. Properties of this material are in a good agreement with the main requirements obligated to biological materials: i) AlN NP has low toxicity; ii) AlN:Mn NP possesses intensive red luminescence at 600 nm, which can be excited either with the ultraviolet light around 260 nm or with visible light around 480 nm; iii) it is relatively cheep material and it can be synthesized using simple synthesis methods.