Recently

low-dimensional structures

such as nanowires

nanoslices and nanotubes

have aroused remarkable attentions due to a great deal potential applications in data storage

advanced catalyst

photoelectronic devices etc. In this paper nanowires were prepared by the hydrothermal method. Appropriate amounts of high purity Gd

2

O

3

Yb

2

O

3

and Er

2

O

3

were dissolved into concentrated HNO

3

solution. Diluted NaOH solution was dripped into the solution to adjust the pHvalues for an appropriate value. After well stirred

the resultants of RE(OH)

3

(

RE

=Gd

Yb

Er) colloidal solution was heated and then was centrifuged and dried. The dried RE(OH)

3

powders were calcined

and finally Gd

2

O

3

:Er

3+

/Yb

3+

nanowires and nanoslices were obtained. The morphology and size of nanowires were obtained by transmission electron micrograph and X-ray diffraction patterns. By controlling the pHvalues

the shape of the nanocrystals varied from two-dimensional nanoslices to one-dimensional nanowires. It was found that the nanoslices were yielded in the chemically neutral conditions and nanowires were yielded in the alkalescent conditions. Emission spectra were studied under the 980 nm diode laser pumping. Green upconversion luminescence of

2

H

11/2

/

4

S

3/2

4

I

15/2

red upconversion luminescence of

4

F

9/2

4

I

15/2

and infrared emissions of

4

I

13/2

4

I

15/2

were observed. The infrared emissions of

4

I

13/2

4

I

15/2

gradually decreased with the increase of pHvalue and the forming of nanowires

while the visible upconversion luminescence of

2

H

11/2

/

4

S

3/2

4

I

15/2

and

4

F

9/2

4

I

15/2

gradually increased

indicating more efficient upconversion luminescence. The relative intensity of the green emissions to the red emissions also increased with the increase of pH value. Electronic relaxation processes dominates the intensity ratio of the upconversion luminescence to the infrared emissions. The ratio of surface atoms to inner atoms in nanowires was decreased in comparison to that in nanoslices

and the nonradiative relaxation was decreased due to a great number of surface defects involved. This led the intensity of upconversion luminescence to increase and the intensity of infrared emission to decrease relatively in nanowires.