Synthesis Of Metal Ion Doped Luminescent Materials And Applications In Development Of Fingermarks

Metal ion doped luminescent materials have been widely applied in lighting, display and many other fields. With the development of science and technology, their applications have been gradually expanding to biomedical, new energy resources, and space technology areas. Although mainstream market has been occupied by new light sources and flat panel displays based on inorganic luminescent materials, their luminous efficiency and color rendering index have to be further improved to meet great demand. Being near ultraviolet (UV) semiconductor chip increasingly mature and further developed forward to short wave UV, luminescent properties of these phosphors will be better utilized. Therefore, the preparation of new high efficient metal ion doped luminescent materials, deep exploration and utilization is particularly urgent.In this work, preparation methods and luminescent properties of SrZn2(PO4)2:Sn2+, Mn2+, Na2SrMg(PO4)2:Ce3+, Mn2+, LiZnPO4:Eu3+, and Zn2Si04:Tb3+, Ce3+ were systematically investigated. Zn2Si04:Mn2+, Er3+, SrAl2O4:Eu2+, Dy3+, and Sr2MgSi207:Eu2+, Dy3+ were synthesized by sol-gel method, high temperature solid state reaction respectively, and firstly applied in development of latent fingermarks on different substrates. The major research contents and appropriate conclusions are as following:1. Preparation and luminescent properties of SrZn2(PO4)2:Sn2+, Mn2+ phosphorsThe technological conditions for preparation of SrZn2(PO4)2:Sn2+, Mn2+ by solid state reaction were investigated in detail. The optimum calcination temperature and the holding time were determined to be 850℃ and 3 hours, respectively. The luminescence properties of SrZn2(PO4)2:Sn2+, Mn2+ and energy transfer from Sn2+ to Mn2+ were investigated. According to the Dexter’s energy transfer formula of multipolar interaction, it was demonstrated that the energy transfer between Sn2+ and Mn2+ was due to the electric quadripole-quadripole interaction of the resonance transfer. The critical distance (Rc) of energy transfer was calculated to be about 2.25 nm. Emission color could be adjusted by changing of Sn2+ and Mn2+ contents. The phosphor has strong blue-white light emission under excitation of 254 nm UV light, and has potential to be used in energy-saving fluorescent lamp.2. Luminescent properties of a novel red phosphor Na2SrMg(PO4)2:Ce3+, Mn2+A novel red phosphor Na2SrMg(PO4)2:Ce3+, Mn2+ was prepared by solid state reaction. The optimum calcination temperature and the holding time were determined to be 900℃ and 3 hours, respectively, there being a phase transition temperature between 900℃ and 950℃ was testified by phase analysis. The luminescence properties and energy transfer from Ce3+ to Mn2+ were systematically investigated. The emission bands of Ce3+ and Mn2+, peaks at 334 nm and 617 nm were attributed to 5dâ†'4f transition of Ce3+ and 4Ti(4G)â†'6Al(6S) transition of Mn2+, respectively. The dependence of Ce3+ and Mn2+ luminescence properties on their doped contents were investigated as well. The optimum contents of Ce3+, Mn2+ were determined to be 4at.%,19at.%, respectively. It was indicated that luminescence of Mn2+ could be sensitized by energy transfer from Ce3+ to Mn2+ in Na2SrMg(PO4)2 host. According to the Dexter’s energy transfer formula of multipolar interaction, it was demonstrated that the energy transfer between Ce3+ and Mn2+ was due to the electric dipole-quadripole interaction of the resonance transfer. The critical distance (Rc) of energy transfer was calculated to be about 1.64 nm.3. Luminescent properties of red phosphor LiZnPO4:Eu3+Red phosphor LiZnPO4:Eu3+ was prepared by solid state method, and the optimum calcination temperature and holding time were determined to be 900℃ and 3 hours by analysis of phase and luminescent properties. The emission of the phosphor at 592 nm is dominant due to there being symmetric center in the crystal structure of LiZnPO4. The emission intensity is up to maximum when Eu3+ content is 12at.%. The critical distance (Rc) of energy transfer was calculated to be about 1.21 nm. The Gd3+ of effect on emission of LiZnPO>4:Eu3+ was investigated in detail, the experimental result indicate that emission intensity of Eu3+ at 592 nm,612 nm was enhanced by 93% and 88%, respectively, and the effect of introduction of Si4+ into the host for substitute of P5+ on luminescent properties of LiZnPO4:Eu3+ was investigated as well, emission intensity of Eu3+ at 592 nm,612 nm was enhanced by 105% and 108%, respectively. It is very significant to reduce the cost of raw materials by decrease of amount of Eu3+. The phosphor is excitable efficiently by 395 nm UV and short wave UV, and used as red component in White LED or fluorescent lamp.4. Luminescent properties of Ba2Mg(BO3)2:Eu2+(3+) phosphorThe preparation conditions of phosphor based on Ba2Mg(BO3)2 host was systematically investigated, effect of Eu3+ content on the host lattice environment and luminescent properties of phosphor as well. The optimum calcination temperature and holding time were determined to be 900℃ and 3 hours. The research results show that Ba2+ is increasingly deviate from symmetric center with increase of Eu3+ content, and result in distortion of crystal structure and formation of two types of Eu3+ luminescent centers. When Eu3+ content is very low, the maximum emission peak of the Ba2Mg(BO3)2:Eu3+ is at 594 nm. However, Eu3+ content is over 3at.%, the emission intensity at 613 nm peak is dramatically enhanced, and is more than that of at the peak of 594 nm in case Eu3+ content is over 3.5at.%, which is attributed to the degree of distortion of crystal structure, and result in obvious change of the symmetric properties of the crystal lattice, thus forbidden electric dipolar 5D0â†'7F2 transition is more released.The effect of reduction atmosphere on the phosphor Ba2Mg(BO3)2:Eu3+,3+ was investigated in detail. Eu2+ and Eu3+ coexist in the host lattice on condition of CO reduction atmosphere, which result in multiple luminescence centers, therefore the phosphor could be selectively excited by 365 nm,395 nm UV. The yellow emission intensity at 564 nm was remarkably enhanced when more Eu3+ were reduced to Eu2+ in atmosphere of H2, but Eu3+ was not totally reduced yet. By means of the control of reduction condition, orange phosphor Ba2Mg(BO3)2Eu:3+ and high brightness yellow phosphor Ba2Mg(BO5)2:Eu2+,3+ were prepared accordingly. Color coordinate of yellow phosphor is very close to white light area, this phosphor could be excited by near UV InGaN chip, combing with blue light, and applied in white LED.5. Preparation of ions doped Zn2SiO4 green phosphor, luminescent properties and application in development of fingermarksZn2SiO4:Tb3+, Zr2SiO4:Ce3+, Zn2SiO4:Tb3+, Ce3+ phosphors were prepared by solid-state reaction at 1150℃ for 2 hours under a weak reducing atmosphere. The X-ray diffraction (XRD) patterns, photoluminescence spectra were recorded and effects of Tb3+ and Ce3+ concentration on the luminescent properties of as-synthesized phosphors were investigated. The emission spectra under ultraviolet light (333 nm) radiation showed a dominant peak at 542 nm attributed to the 5D4â†'7F5 transition of Tb3+, which was enhanced significantly (about 45 times) by the co-doping of Ce3+, indicating that there occurred an efficient energy transfer from Ce3+ to Tb3+. According to the Dexter’s energy transfer formula of multipolar interaction, and luminescence life time, it was demonstrated that the energy transfer between Ce3+ and Tb3+ was due to the electric dipolar-dipolar interaction of the resonance transfer. The critical distance (Rc) of energy transfer was calculated to be about 2.75 nm. Zn2SiO4:Tb3+,Ce3+ is excited efficiently by 340～365 nm UV, and the high lightness green phosphor could be used as light-converted material in white LED.Micro and nano fluorescent powders Zn2SiO4:Mn2+,Er3+(ZSME) were prepared by sol-gel method combined with ultrasonic dispersion. In this contribution. Micro and nano-fluorescent powder was introduced to development of fingermarks on non-porous and semi-porous substrates, and image of fingermarks. Compared with organic nano fluorescent powders (Roar Partilce Ltd., UK), the micro and nano fluorescent powder ZSME was more applicable for latent fingermarks detection on various substrates, including painted wood, marble, glass, phone card, and leather. It was quite significant that third level could be revealed, background disturbance of substrates was effectively diminished, and high-contrast imaging was achieved using ZSME powders for fingermarks detection.6. Development of latent fingermarks and time-resolved imaging by using long afterglow phosphorsConventional development of latent fingerprints is compromised when the prints are on the difficult and patterned substrates. In consideration of this problem, Eu2+, Dy3+ co-doped SrAl2O4 (SED) and Sr2MgSi2O7 (SMSED) were synthesized by sol-gel method and solid-state reaction, respectively. It was characterized by XRD, and photoluminescence (PL) spectrometer respectively. Owing to super long afterglow properties of them, the phosphors were introduced to development of fingerprints on non-porous and semi-porous substrates, and image of fingerprints, Compared with the nano organic fluorescent powders, long afterglow phosphors are more applicable for latent fingerprint detections on various substrates, including glass, ceramic tile, plastic, smooth hard paper, print paper, and leather. All the results illustrated that long afterglow phosphors are ideal reagent for fingermarks detection due to elimination of background interferences from various difficult substrates, and offered a good contrast to allow their identification without the need to enhance the results compared to the organic nano fluorescent powders. At the same time, compared to SED, SMSED is better compatible to humid environment.Innovative point of this paper is:1. Novel blue-white phosphor SrZn2(PO4)2:Sn2+, Mn2+, red phosphor Na2SrMg(PO4)2:Ce3+, Mn2+ were firstly prepared. Energy transfer principle of Sn2+-Mn2+, Ce3+-Mn2+ in the materials was investigated. For Na2SrMg(PO4)2, there is a phase transition temperature between 900℃ and 950℃ was testified by phase analysis.2. The effect of Eu3+ content on luminescent of LiZnPO4:Eu3+ was systematically investigated. The emission intensity of LiZnPO4:Eu3+ was efficiently enhanced by introduction Gd3+ and Si4+ into host material. It is very significant to reduce the cost of raw materials by decrease of amount of Eu3+.3. The effect of Eu3+ content on the host lattice environment and luminescent properties of phosphor was investigated in detail, and the effect of reduction atmosphere on the phosphor Ba2Mg(BO3)2:Eu2+,3+ as well. By means of the control of reduction condition, high brightness yellow phosphor Ba2Mg(BO3)2:Eu2+,3+ was prepared.4. Green phosphor Zn2SiO4:Tb3+,Ce3+ was firstly prepared, and energy transfer principle of Ce3+-Tb3+ in Zn2SiO4 was investigated.5. It is first time to apply micro and nano fluorescent powder Zn2Si04:Mn2+, Er3+, long afterglow phosphors SrAl2O4:Eu2+, Dy3+ and Sr2MgSi207:Eu2+, Dy3+ to development of latent fingermarks. Background disturbance of difficult and patterned substrates was effectively eliminated or diminished, and time-resolved imaging was achieved using long afterglow phosphors for fingermarks detection.