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3D hierarchical GdPO 4 ·H 2 O:Ln 3+ (Ln 3+ = Eu 3+ , Ce 3+ , Tb 3+ ) flower clusters were successfully prepared on glass slide substrate by a simple, economical hydrothermal process with the assistance of disodium ethylenediaminetetraacetic acid (Na 2 H 2 L, where L 4− = (CH 2 COO) 2 N(CH 2 ) 2 N(CH 2 COO) 2 4− ). In this process, Na 2 H 2 L was used as both a chelating agent and a structure-director. The hierarchical flower clusters have an average diameter of 7–12 μm and are composed of well-aligned microrods. The influence of the molar ratio of Na 2 H 2 L/Gd 3+ and reaction time on the morphology was systematically studied. A possible crystal growth and formation mechanism of hierarchical flower clusters is proposed based on the evolution of morphology as a function of reaction time. The self-assembled GdPO 4 ·H 2 O:Ln 3+ superstructures exhibit strong orange-red (Eu 3+ , 5 D 0 → 7 F 1 ), green (Tb 3+ , 5 D 4 → 7 F 5 ) and near ultraviolet emissions (Ce 3+ , 5d → 7 F 5/2 ) under ultraviolet excitation, respectively. This study may provide a new channel for building hierarchically superstructued oxide micro/nanomaterials with optical and new properties.

The flower-like GdVO 4 :Ln 3+ ( Ln 3+ =Eu 3+ , Dy 3+ , Sm 3+ , Tm 3+ ) hierarchitectures have been successfully synthesized on a glass slide substrate through a one-pot hydrothermal route assisted by disodium ethylenediaminetetraacetic acid (Na 2 H 2 L, where L 4- =(CH 2 COO) 2 N(CH 2 ) 2 N(CH 2 COO) 2 4- ). A high density and ordered flower-like GdVO 4 :Ln 3+ hierarchitectures grew epitaxially on glass substrate. The as-prepared flower-like architectures with the size about 6 μm are constructed by the numerous radially oriented single-crystalline nanorods with the width from 20 nm to 200 nm and the length from 500 nm to 3 μm. The morphologies, the thickness, and the density of as-grown flower clusters can be readily tuned by tailoring the growth time and Na 2 H 2 L/Gd 3+ molar ratio. The possible formation mechanism of flower-like GdVO 4 :Ln 3+ hierarchitectures is discussed on the basis of the results from the controlled experiments under hydrothermal conditions. Because of an energy transfer from vanadate groups to dopants, the flower-like GdVO 4 :Ln 3+ ( Ln 3+ =Eu 3+ , Dy 3+ , Sm 3+ and Tm 3+ ) superstructures showed strong characteristic dominant emissions of the Eu 3+ , Dy 3+ , Sm 3+ and Tm 3+ ions at 617 nm ( 5 D 0 → 7 F 2 , strong red), 575 nm ( 4 F 9/2 → 6 H 13/2 , yellow), 604 nm ( 4 G 5/2 → 6 H 7/2 , orange-red) and 476 nm ( 1 G 4 – 3 H 6 , blue) under ultraviolet excitation, respectively.Further, the emission color of the product can also be tuned by selecting the dopant Ln 3+ with characteristic emissions and varying the concentration ratio of co-doping activators. This approach could be extended to the fabrication of hierarchical structures for other oxide micro/nanomaterials, and may provide a general way to achieve multicolor-tunable emission for many applications.

Tetragonal t-LaVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+) microrod array and 3D hierarchical nanostructures with sheaf-like, flower-like, cauliflower-like, and spherical morphologies have been successfully synthesized on glass substrate through a simple hydrothermal process assisted by ethylenediaminetetraacetic acid disodium salt (Na2H2L). The morphologies of the products varied dramatically when Na2H2L/La3+ molar ratio and reaction time were changed in system. A possible crystal growth mechanism is proposed for the self-assembly of nanorods into the observed microstructures based on detailed experiments. Due to an efficient energy transfer from VO4 3− to the Ln3+ dopants, the self-assembled t-LaVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+) superstructures showed strong characteristic dominant emissions of the Eu3+, Dy3+, Sm3+ ions at 616 nm (5D0 → 7F2, strong red), 573 nm (4F9/2 → 6H13/2, yellow), 603 nm (4G5/2 → 6H7/2, orange-red) under ultraviolet excitation, respectively. This work not only gives insight into understanding the hierarchical growth behaviour of t-LaVO4:Ln3+ nanoarchitectures in a solution-phase system, but also provides a potential route to building other superstructures assembled from one-dimensional nanoparticles.

Novel three-dimensional YVO4:Ln3+ (Ln3+ = Eu3+, Sm3+, Dy3+, Tm3+) hierarchitectures were successfully fabricated on glass substrate by a simple, hydrothermal process by using disodium ethylenediaminetetraacetic acid (Na2H2L, where L4− = (CH2COO)2N(CH2)2N(CH2COO)24−)) as a capping agent. The shape and size of product can be tailored by controlling the reaction time and the Na2H2L/Y3+ molar ratio. As a typical morphology, YVO4:Eu3+ shows a flower-like hiearchitecture, which is composed of a primary microrod trunk and a large number of secondary nanonails. The trunk is a rectangle prism with a length of 2 μm. The nanonail branch has a length of 400 nm and a diameter of 80 nm, and its cap has a diameter of 100 nm with a thickness of 20 nm. A possible formation mechanism of this flower-like hierarchical structure was proposed, and it is investigated in detail through time evolution experiments. Under UV radiation, the thin film samples were shown the emission characteristic of Eu3+ (5D0→7F2, 618 nm), Dy3+ (4F9/2 → 6H13/2, 575 nm), Sm3+ (4G5/2 → 6H7/2, 603 nm), Tm3+ (1G4→3H6, 478 nm), and morphology-sensitive photoluminescent properties.