Langmuir 2007, 23, 10873-10873
10873
Comments Comment on High-Quality Luminescent Tellurium Nanowires of Several Nanometers in Diameter and High Aspect Ratio Synthesized by a Poly (Vinyl Pyrrolidone)-Assisted Hydrothermal Process
In a recent publication, Qian et al.1 have reported blue-violet emission using 365 nm excitation wavelength from ultrathin tellurium (Te) nanowire samples (Figure 11b of ref 1) prepared by them. We are also working on Te nanowires, and we have carried out similar measurements on Te nanowire/tube samples. The samples were spread on glass slides (∼1 mm thick) as usual, and photoluminescence (PL) spectra were recorded using 365 nm excitation wavelength in a spectrometer (Hitachi model F-4500) using the standard solid sample holder (a spring loaded metallic sample holder with a black polymer cushion support for holding the samples) provided with the instrument. We also observed exactly the same blue-violet emission from our samples. However, repeated and careful experiments revealed beyond doubt that the emission was actually coming not from our samples but from the sample holder itself. We show in Figure 1 PL spectra from the sample holder only (without any sample) after suitably cleaning it. The peaks were confirmed as emission lines, since changing the exciting wavelength in the 350-375 nm range did not shift their emission spectra. To recheck if there was any error in the detector system, measurements were carried out without the sample holder, and no emission could be seen. The results of Figure 1 are repeatable even after cleaning the sample holder several times. The spectrum in Figure 1 was deconvoluted using multi-Gaussian line shapes. The deconvoluted features are also surprisingly similar to that reported by Qiang et al.1 for their ultrathin nanowire samples. Regarding the origin of the emission lines, it could be either the black polymer cushion used in the sample holder or the glue used to fix it. Interestingly, we could not observe any blue-violet emission for our samples when they were recorded carefully using a thick glass and/or metal separator between the holder and the glass slide. We may add that, in agreement to our finding, Gautam and Rao in their article2 did not report any blue-violet emission from nc-Te samples when * To whom correspondence should be addressed. Telephone: 91-2225590292. Fax: 91-22-25505151. E-mail:
[email protected] (M.R.);
[email protected] (A.K.T.). † Chemistry Division. ‡ Technical Physics and Prototype Division. (1) Qian, H.-S.; Yu, S.-H.; Gong, J.-Y.; Luo, L.-B.; Fei, L.-f. High-Quality Luminescent Tellurium Nanowires of Several Nanometers in Diameter and High Aspect Ratio Synthesized by a Poly (Vinyl Pyrrolidone)-Assisted Hydrothermal Process. Langmuir 2006, 22, 3830. (2) Gautam, U. K.; Rao, C. N. R. Controlled synthesis of crystalline tellurium nanorods, nanowires, nanobelts and related structures by a self-seeding solution process. J. Mater. Chem. 2004, 14, 2530.
Figure 1. Emission spectra along with the deconvoluted features obtained from the bare sample holder (no sample) of the F-4500 spectrometer (Hitachi). The spectrum without the sample holder is also shown.
excited at similar wavelengths. Samples with nanowires usually have gaps between the wires, and so a PL contribution from the holder (if it emits) can always arise because light can pass “to and from” through the glass slide. This could also have happened in the case of the study presented by Qiang et al.1 We may add that the sample holder of the spectrometer (Hitachi F-4010) also showed emission around the same wavelength range with slight variation in the spectral profile when excited at 365 nm. The information provided in this communication that the standard solid sample holders provided with commercial spectrophotometers emit in the blue-violet region when excited near 365 nm is of importance to the scientific community. Acknowledgment. The authors are thankful to Dr. H. Pal, Radiation Photochemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, India, and Dr. A. Datta, Department of Chemistry, Indian Institute of Technology, Mumbai-400076, India, for their fruitful suggestions and discussions. M. Roy,*,† Shashwati Sen,‡ S. K. Gupta,‡ and A. K. Tyagi*,†
Chemistry DiVision and Technical Physics and Prototype DiVision, Bhabha Atomic Research Centre, Mumbai-400085, India
10.1021/la701269g CCC: $37.00 © 2007 American Chemical Society Published on Web 09/13/2007
ReceiVed May 1, 2007 LA701269G
