Riya Dey

Photoluminescence study of Y2O3:Er3+-Eu3+-Yb3+ phosphor for lighting and sensing applications

The Er3+, Eu3+, and Yb3+ codoped Y2O3 phosphors have been synthesized by combustion synthesis process. For the structural information, the XRD analysis of the developed phosphor has been done. The frequency upconversion (UC) emissions in the codoped Y2O3 phosphor on excitation with 980 nm diode laser in the visible region have been performed and explained on the basis of excited state absorption and energy transfer process. The mechanism responsible in UC emissions was observed to involve two photon absorption and efficiency of the UC luminescence is significantly enhanced by introducing the Yb3+ ions. The tunability in colour of emitted radiation has been visualized by chromaticity diagram on increasing power of excitation source. The temperature sensing behaviour of developed phosphor material has been investigated using fluorescence intensity ratio technique.

Stark sublevels in Tm3+–Yb3+ codoped Na2Y2B2O7 nanophosphor for multifunctional applications

The phase and crystal structure of the Na2Y2B2O7:Tm3+–Yb3+ inorganic phosphor prepared by solution combustion method have been identified by powder X-ray diffraction technique. Surface morphology and particle size have been examined using field emission scanning electron microscopy and high resolution transmission electron microscopy characterizations of the prepared materials. No absorption band around 980 nm has been observed in the Tm3+ doped phosphors, whereas a broad band around 980 nm in the Tm3+–Yb3+ codoped phosphors corresponding to the 2F7/2 ← 2F5/2 absorption transition of Yb3+ ion has been detected. Upconversion emission bands have been observed in the UV, visible and NIR regions upon excitation with a 980 nm laser diode. The temperature sensing behaviour and the concept of a nanoheater of the developed nanophosphor have been demonstrated by using the stark sublevels of the 1G4 level of the Tm3+ ion, which are responsible for the blue upconversion emission. A maximum sensor sensitivity of about 4.54 × 10−3 K−1 at 300 K for the developed multifunctional nanophosphor has been determined. A temperature gain of about ∼435 K has been observed at a laser power density of 66.88 W cm−2 and the colour coordinates do not change with the variation of the pump power density. For localizing and heating hyperthermia based cancer cells using NIR radiation, a very low pump power density of about ∼7.0 W cm−2 has been established. The experimental observations prove that the developed material can be used as a multifunctional nanomaterial in optical devices and biological applications.

Simultaneous influence of Zn2+/Mg2+ on the luminescent behaviour of La2O3:Tm3+–Yb3+ phosphors

The structural characterizations of La2O3 phosphors doped/codoped with Tm3+ and Yb3+ ions synthesized by the urea assisted solution combustion technique were performed using X-ray diffraction analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Codoping with Zn2+/Mg2+ ions causes an increase in the particle size and aggregation for the La2O3:Tm3+–Yb3+ phosphor. The upconversion (UC) study under 980 nm excitation shows four UC emission bands centred around 476 nm (1G4 → 3H6), 653 nm (1G4 → 3F4), 702 nm (3F2 → 3H6) and 795 nm (1G4 → 3H5). The effect of codoping with Zn2+ and Mg2+ ions in the Tm3+–Yb3+ codoped La2O3 phosphor was investigated. Decay curve analysis of the prepared phosphors was done to understand the mechanism of the upconversion emission intensity variation due to codoping with Zn2+/Mg2+ ions. The purity of colour emitted from the sample does not show any change with variations in pump power density.

Green upconversion emission in Nd3+–Yb3+–Zn2+:Y2O3 phosphor

The Y(2)O(3) phosphor powder codoped with Nd(3+):Yb(3+) ions have been synthesized through optimized combustion route. Crystalline structures of the prepared samples have been investigated by powder X-ray diffraction technique. Efficient upconversion emission in the green region upon 980 nm NIR CW diode laser excitation has been reported. The maximal enhancement in the intensity of the green upconversion emission band has been observed on codoping with Zn(2+) ions in the Nd(3+):Yb(3+) codoped sample. The processes responsible for such an enhancement in the green upconversion emission band which can be used for the localization and diagnosis of cancer has been explained in detail.

The Er3+-Yb3+ codoped La2O3 phosphor in finger print detection and optical heating.

The presence of impurities and morphological information about the Er(3+)-Yb(3+) codoped La2O3 phosphors prepared by two different synthesis techniques have been obtained with the help of Fourier transform infrared (FTIR) spectroscopy and Scanning electron microscopy (SEM) respectively. The effect of synthesis process on the frequency upconversion (UC) emission with an excitation at 980 nm from laser diode radiation has been performed. The use of codoped phosphor in latent finger print detection and laser induced heat generation has also been explored.

pH controlled Ho3+–Yb3+ codoped Y2O3 nanowires for display devices

The wire like structure with particle size in the nanometer range of Ho(3+)-Yb(3+) codoped Y2O3 phosphors have been synthesized through hydrothermal synthesis route by controlling the pH value. The Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analysis of the synthesized phosphor powders have been studied which confirms the formation of nanowires in the prepared materials and the formation of proper crystalline structure respectively. The frequency upconversion emission spectra under 980 nm excitation have been recorded and an efficient green emission has been observed. The excitation energy corresponding to the NIR photon seems to be fully utilized for the emission lying in the green region. The Fourier transform infrared (FTIR) spectroscopic analysis for existence of the impurities in the developed material has also been performed. The experimental observation proves the utility of the prepared material in the display devices and diagnosis purposes.

Sensitization Effect of Yb3+ in Upconversion Luminescence of Eu3+Codoped Y2O3 Phosphor

For structural information, the X-ray diffraction analysis of Y2O3:Eu3+ phosphors codoped with Yb3+ synthesized by combustion synthesis process has been performed. The upconversion emission study of the Y2O3:Eu3+ phosphor codoped with Yb3+ ions on excitation with 980 nm diode laser in the visible region has been done. The upconversion emissions corresponding to the Eu3+ ions is due to sensitization from Yb3+ ions in developed phosphor, and has been explained on the basis of cooperative energy transfer process. The orange colour emitted from the codoped samples is visualized by CIE diagram. The results show the applicability of the present phosphor as suitable NIR (near infrared) to visible upconverter, and in other photonic devices.

White upconversion emission in Y{sub 2}O{sub 3}:Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+}phosphor

Graphical abstract: Schematic energy level diagram of Er{sup 3+}–Yb{sup 3+}–Tm{sup 3+} system upon excitation at 980 nm. Highlights: ► Prepared the Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor. ► Excitation of the sample by 980 nm diode laser is studied. ► Explored the possibility of getting white light emission from the synthesized phosphor. ► Colour tunability of the prepared phosphor is studied. ► Temperature sensing behaviour is investigated using FIR studied. - Abstract: Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor has been synthesized by optimized combustion synthesis process and its white light upconversion emission property is investigated using cheap 980 nm diode laser excitation. Efficient red, green and blue light emission bands, necessary for attaining white light emission, are observed in the codoped sample. The concentration of each rare earth ion is adjusted to get the required emission. In this phosphor, interestingly, emission colour coordinates are found to almost independent on the excitation power density. The temperature sensing behaviour of the prepared samples has also been studied using fluorescence intensity ratio (FIR) technique.Graphical abstract: Schematic energy level diagram of Er{sup 3+}–Yb{sup 3+}–Tm{sup 3+} system upon excitation at 980 nm. Highlights: ► Prepared the Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor. ► Excitation of the sample by 980 nm diode laser is studied. ► Explored the possibility of getting white light emission from the synthesized phosphor. ► Colour tunability of the prepared phosphor is studied. ► Temperature sensing behaviour is investigated using FIR studied. - Abstract: Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor has been synthesized by optimized combustion synthesis process and its white light upconversion emission property is investigated using cheap 980 nm diode laser excitation. Efficient red, green and blue light emission bands, necessary for attaining white light emission, are observed in the codoped sample. The concentration of each rare earth ion is adjusted to get the required emission. In this phosphor, interestingly, emission colour coordinates are found to almost independent on the excitation power density. The temperature sensing behaviour of the prepared samples has also been studied using fluorescence intensity ratio (FIR) technique.

Multicolour upconversion emission from Ho3+-Tm3+-Yb3+ codoped CaMoO4 phosphor

The Ho3+-Tm3+-Yb3+ codoped CaMoO4 phosphor powder has been synthesized by chemical coprecipitation technique. For the structural investigation the X-ray diffraction analysis has been done. Multicolour upconversion (UC) emission in the visible region from the prepared material has been observed under the 980 nm near infrared (NIR) excitation. The UC emission bands ∼ 474 nm (blue), ∼ 541 nm (green) and ∼ 661 nm (red) region have been assigned as 1G4→3H6 (Tm3+), 5F45S2→5I8 (Ho3+) and 5F5→5I8 (Ho3+) transitions respectively.

Effect of codoping of Zn 2+ ion on the upconversion of Er 3+ -Yb 3+ codoped Y 2 O 3 phosphor

The frequency upconversion emission from Er³⁺-Yb³⁺ codoped Y₂O₃ phosphor synthesized by low temperature, urea assisted combustion technique has been studied upon excitation at 980 nm diode laser. The effect of incorporation of Zn²⁺ ion on upconversion (UC) emission bands around 409 nm, 523 nm, 551 nm, 661 nm arises due to the transitions ²H_9/2 → ⁴I_15/2, ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 of Er³⁺ ions have been investigated. The basic mechanism involved in UC process and reason of intensity enhancement on Zn²⁺ codoping have been explained by energy level structure and decay time analyses. The present study indicates that the developed phosphors may be of significant interest for use in photonic applications.