• Journal of Powder Materials
• /
• v.24 no.6
• /
• pp.477-482
• /
• 2017

Nitrogen-doped titanium dioxide (N-doped $TiO_2$) is attracting continuously increasing attention as a material for environmental photocatalysis. The N-atoms can occupy both interstitial and substitutional positions in the solid, with some evidence of a preference for interstitial sites. In this study, N-doped $TiO_2$ is prepared by the sol-gel method using $NH_4OH$ and $NH_4Cl$ as N ion doping agents, and the physical and photocatalytic properties with changes in the synthesis temperature and amount of agent are analyzed. The photocatalytic activities of the N-doped $TiO_2$ samples are evaluated based on the decomposition of methylene blue (MB) under visible-light irradiation. The addition of 5 wt% $NH_4Cl$ produces the best physical properties. As per the UV-vis analysis results, the N-doped $TiO_2$ exhibits a higher visible-light activity than the undoped $TiO_2$. The wavelength of the N-doped $TiO_2$ shifts to the visible-light region up to 412 nm. In addition, this sample shows MB removal of approximately 81%, with the whiteness increasing to +97 when the synthesis temperature is $600^{\circ}C$. The coloration and phase structure of the N-doped $TiO_2$ are characterized in detail using UV-vis, CIE Lab color parameter measurements, and powder X-ray diffraction (XRD).

• Korean Chemical Engineering Research
• /
• v.57 no.3
• /
• pp.331-337
• /
• 2019

Titania has become the most applicable material for photocatalytic application. Nevertheless, titania has the weak point in its wide band gap energy that is mainly activated by UV irradiation. There have been vast research challenges in order to make the wide band gap energy of titania narrow that could be activated in the presence of visible light. Various modifications of titania surface were popular because titania needs to change its surface to respond in visible light. Among the methodological approaches, N-doping to titania can be the alternative candidate because it is facile process and eco-friendly. The activated electron from valence band in N-doped $TiO_2$ migrates to conduction band in the presence of visible light irradiation, which shows photocatalytic activity as well. In this study, focused on the evaluation of nitrogen state after N-doping through brief review. Arguments are still existed in nitrogen states and their different effects on photocatalytic activity. In particular, two nitrogen states are generally reported; substitutional and interstitial states. The research articles regarding N-doped $TiO_2$ are continuously appearing because the potential application of water split in visible light is still fascinate. The future of N-doped $TiO_2$ is also presented by referrals based on various literature.

• Applied Chemistry for Engineering
• /
• v.29 no.3
• /
• pp.298-302
• /
• 2018

Photocatalytic properties of nitrogen doped titanium dioxide were investigated. Photocatalytic degradation of methylene blue under UV and visible light was carried out to characterize N-doped $TiO_2$. The result of XPS indicated that nitrogen atoms substitute for oxygen sites within the crystal structure of $TiO_2$. In the UV-Vis DRS spectra, N-doped amorphous $TiO_2$ absorbed UV light with little absorption of visible light, while the absorption of visible light of amorphous/anatase $TiO_2$ remarkably increased. Methylene blue photocatalytic degradation appeared by the irradiation of UV or visible light onto the N-doped anatase phase of $TiO_2$. However, the degradation rate of visible light was lower than that of UV light. The photocatalytic degradation rate of the amorphous/anatase $TiO_2$ sample was higher than that of the anatase $TiO_2$. These results indicate that the high surface area of amorphous/anatase $TiO_2$ sample, which was about three times larger than those of the anatase $TiO_2$ sample, may be related to small particles of N-doped anatase $TiO_2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.15-16
• /
• 2008

We have grown N-doped ZnO thin films on sapphire substrate by employing dielectric barrier discharge in pulsed laser deposition (DBD-PLD). DBD guarantees an effective way for massive in-situ generation of N-plasma under the conventional PLD process condition. Low-temperature photoluminescence spectra of the N-doped ZnO film provided near band-edge emission after thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound exciton peak ($A^0X$) that indicated the successful p-type doping of ZnO with N.

• Journal of Electrochemical Science and Technology
• /
• v.5 no.2
• /
• pp.49-52
• /
• 2014

Graphene nanosheets (GNS), nitrogen-doped graphene nanosheets (N-GNS), and sulfur-doped graphene nanosheets (S-GNS) were successfully synthesized, and their catalytic effects on the oxygen reduction reaction (ORR) in $Li-O_2$ batteries were compared. The S-GNS electrode exhibited the highest ORR catalytic activity, resulting in enhanced discharge capacity and power capability. We attributed the enhanced ORR catalytic activity to the increased defect sites on graphene.

• Rapid Communication in Photoscience
• /
• v.3 no.1
• /
• pp.20-24
• /
• 2014

N-doped anatase $TiO_2$ nanoparticles were prepared by the sol-gel process followed by a hydrothermal treatment and successfully used as the photoanodes in organic dye-sensitized solar cells (DSSCs). As expected, the power conversion efficiency (PCE) of 8.44% was obtained for the NKX2677/HC-A-sensitized DSSC based on the 30 mol% N-doped $TiO_2$ photoanode, which was an improvement of 23% relative to that of the DSSC based on the NKX2677/DCA.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.11
• /
• pp.1992-1994
• /
• 2007

In this paper we propose a cryogenic sensor system which can measure the temperature at higher resolution at low temperature using temperature-dependent amplified spontaneous emission of erbium-doped fiber pumped by a 1480 nm laser diode. The measurement resolution of the sensor system could be enhanced through the modulation of injection current of the pump laser diode. The measurement resolution considering the fluctuation of the light source in the sensor system was ${\sim}0.4$ K in the room temperature regime and ${\sim}0.07$ K in the liquid nitrogen temperature regime.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.12
• /
• pp.1371-1374
• /
• 2001

Metal doping was adopted to modify TiO2 (P-25) and enhance the photocatalytic degradation of harmful cyanides in aqueous solution. Ni, Cu, Co, and Ag doped TiO2 were found to be active photocatalysts for UV light induced degradation of aqueous cyanides generating cyanate, nitrate and ammonia as main nitrogen-containing products. The photoactivity of Ni doped TiO2 was greatly affected by the state of Ni, that is, the crystal size and the degree of reduction of Ni. The modification effects of some mixed oxides, that is, Ni-Cu/TiO2 were also studied. The activity of Ni-Cu/TiO2 for any ratio of Cu/Ni was higher than that of Ni- or Cu-doped TiO2, and the catalyst at the Cu/Ni ratio of 0.3 showed the highest activity for cyanide conversion.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.3
• /
• pp.195-202
• /
• 1998

The LPCVD system of batch type for the massproduction of semiconductor fabrication has a problem of phosphorous concentration uniformity in the boat. In this paper we study an improvement of the uniformity for phosphorous concentration and sheet resistance. These property was improved by using the nitrogen process and modified long nozzle for gas injection tube in the doped polysilicon deposition system. The phosphorous concentration and its uniformity for polysilicon film are measured by XRF(X-ray Fluorescence) for the conventional process condition and nitrogen process. In conventional process condition, the phosphorous concentration, it uniformity and sheet resistance for polysilicon film are in the range of 3.8~5.4$\times$10\ulcorner atoms/㎤, 17.3% and 59~$\Omega$/ , respectively. For the case of nitrogen process the corresponding measurements exhibited between 4.3~5.3$\times$10\ulcorner atoms/㎤, 10.6% and 58~81$\Omega$/ . We find that in the nitrogen process the uniformity of phosphorous concentration improved compared with conventional process condition, however, the sheet resistance in the up zone of the boat increased about 12 $\Omega$/ . In modified long nozzle, the phosphorous concentration, its uniformity and sheet resistance for polysilicon films are in the range of 4.5~5.1$\times$10\ulcorner atoms/㎤, 5.3% and 60~65$\Omega$/ respectively. Annealing after $N_2$process gives the increment of grain size and the decrement of roughness. Modification of nozzle gives the increment of injection amount of PH$_3$. Both of these suggestion result in the stable phosphorous concentration and sheet resistance. The results obtained in this study are also applicable to process control of batch type system for memory device fabrication.

• Korean Journal of Materials Research
• /
• v.24 no.10
• /
• pp.565-571
• /
• 2014

Nitrogen-doped ZnO nanoparticle-carbon nanofiber composites were prepared using electrospinning. As the relative amounts of N-doped ZnO nanoparticles in the composites were controlled to levels of 3.4, 9.6, and 13.8 wt%, the morphological, structural, and chemical properties of the composites were characterized by means of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the carbon nanofiber composites containing 13.8 wt% N-doped ZnO nanoparticles exhibited superior catalytic properties, making them suitable for use as counter electrodes in dye-sensitized solar cells (DSSCs). This result can be attributed to the enhanced surface roughness of the composites, which offers sites for $I_3{^-}$ ion reductions and the formation of Zn3N2 phases that facilitate electron transfer. Therefore, DSSCs fabricated with 13.8 wt% N-doped ZnO nanoparticle-carbon nanofiber composites showed high current density ($16.3mA/cm^2$), high fill factor (57.8%), and excellent power-conversion efficiency (6.69%); at the same time, these DSSCs displayed power-conversion efficiency almost identical to that of DSSCs fabricated with a pure Pt counter electrode (6.57%).