Rare Earth Doped Optical Fibers for Temperature Sensing Utilizing Ratio-Based Technology

A new and practical fluorescence temperature detecting system based on fluorescence intensity ratio was proposed . The background theory of fluorescence intensity-ratio method was presented simply. And the characters of rare earth doped samples were detailed. The erbium-doped fiber was chosen as the sensing element. The energy levels of 2H11/2 and 4S3/2 are responsible for the emission of radiation at approximately 530 and 555 nm. The erbium-doped (960 ppm) fiber of length 20 cm and core diameter 3.2μm was used as the sensing part. A silica photodiode transfers the fluorescence signal to electric signal, then the ratio of the average of the two different signals was calculated by the computer and the temperature was obtained. The ratio R of the intensity resulting from the transition between the two levels varies proportionly with temperature interval from 293 K to 373 K. The sensitivity of the sensor is approximately 0.05 K-1.

Effects of salinity and nutrients on the growth and chlorophyll fluorescence of Caulerpa lentillifera

Caulerpa lentillifera is a green algae that distributes worldwide and is cultivated for food. We assessed vegetative propagation of C. lentillifera by measuring the specific growth rate （SGR） and chlorophyll fluorescence of the green algae cultured at different salinities and nutrient levels. The results indicated that C. lentillifera can survive in salinities ranging from 20 to 50, and can develop at salinities of 30 to 40. The maximum SGR for C. lentillifera occurred at a salinity of 35. Both chlorophyll content and the ratio of variable to maximum fluorescence （F_v/F_m） were also at a maximum at a salinity of 35. Photosynthesis was inhibited in salinities greater than 45 and less than 25. Both the maximum SGR and maximum chlorophyll content were found in algae treated with a concentration of 0.5 mmol/L of NO3-N and 0.1 mmol/L of PO_4-P. The photosynthetic capacity of photosystem Ⅱ （PSⅡ） was inhibited in cultures of C. lentillifera at high nutrient levels. This occurred when NO_3-N concentrations were greater than 1.0 mmol/L and when PO4-P concentrations were at 0.4 mmol/L. As there is strong need for large-scale cultivation of C. lentillifera, these data contribute important information to ensure optimal results.

Fluorescence Determination of Artemisinin Using Hemoglobin as Catalyst and Pyronine B as Substrate

Fluorescence decrease ratio was applied to determine of arte misinin （qinghaosu, QHS） based on the catalytic effect of hemoglobin （Hb） using tetraethyldiaminoxanthenyl chloride （Pryonine B, PB） as monitor in this work, Experimental results show that the catalytic characteristics of Hb for QHS, being expressed as Michaelis-Menten parameters, Km, Vmax and Kcat are 2.8×10^-5 mol·L^-1, 4.2×10^-5 mol·L^-1·s^-1 and 280 s^-1 , respectively. Like hemin, enzymatic bioactivities of Hb is inhibited by both deactivated agents and high temperature whereas enhanced by ethanol. With the catalytic action of Hb, quantitative method of QHS can be established based on the fluorescence decrease of PB and linear relationship between the fluorescence decrease ratio F0/F and the concentration of QHS is in the range of （0.0-1.1）×10^-6 mol·L^-1 with detection limit （3σ） being 7. 2×10^-9 mol·L^-1, The concentration of QHS in the media of plasma or urine was detected using this method.

A ratiometric optical thermometer with dual-color emission based on Eu^(2+)-doped CsCu_(2)I_(3) microcrystals

With the increasing demand for non-co ntact fluorescence intensity ratio-based optical thermometry,novel phosphor materials with high-efficiency,dual-emitting centers,and differentiable temperature sensitivity are highly desired,In this wo rk,rare earth Eu^(2+) ions were incorporated Wnto CsCu_(2)I_(3) microcrystals by solidstate reaction,Under a single UV excitation,the as-synthesized samples exhibit two emissions:452 nm blue emission from the 5d→4f transition of Eu^(2+)and 582 nm yellow emission from self-trapped exciton e mission of CsCu_(2)I_(3).The photoluminescence quantum yield reaches to 50%,The dual-band emission of Eu^(2+)-doped CsCu_(2)I_(3) shows different temperature responses in the range of 260-360 K.Based on fluorescence intensity ratio technology,the maximum absolute sensitivity and re Iative sensitivity are 0.091 K^(-1)(at 360 K) and 2.60%/K(at 260 K),respectively.These results suggest that Eu^(2+)-doped GsCu_(2)I_(3) could be a good candidate for highly sensitive optical thermometer.

Construction of AIEgen functionalized nanomicelles and their stability study through‘seesaw-like'fluorescence changes

As nanocarriers,nanomicelles play vital roles in the toolbox of drug delivery.The stability of nanomicelles affects the nanomedicines'bioactivity.Therefore,it is important to understand the stability of nanomicelles for further improvements.Here,we report a strategy to construct new nanomicelles(NM)by introducing aggregation-induced emission(AIE)functional group tetraphenylethylene(TPE)in the component polymer vitamin E(D-α-tocopheryl polyethylene glycol 1000 succinate)(TPGS).The stability of doxorubicin(DOX)loaded nanomicelles DOX@NM in different conditions was studied by fluorescence analysis.The fluorescence changes of DOX@NM are‘seesaw-like'when they transform between assembled and disassembled forms.In the assembled form,TPE gives emission from AIE effect,while in the disassembled form,the fluorescence of DOX is observed due to the disappearance of ACQ effect.

An abnormal fluorescence intensity ratio between two green emissions of Er^(3+) caused by heating effect of 980 nm excitation

An abnormal fluorescence intensity ratio （FIR） between two green emissions of Er3＋, at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has seldom been done to clarify this abnormal phenomenon. In this paper, green upconversion luminescence of the β-NaLuF4：20%yb3＋,2%Er3＋ powder sample was investigated under 980 um excitation at different circumstances, different pump power densities and different temperatures as well as different air pressures. The corresponding local temperature calculated using FIR technique increased gradually with the enhancement of the pump power density. It was demonstrated that high pump power density of 980 nm laser led to the increase of local temperature of the luminescent material, which further gave the abnormal FIR.

Green and red up-conversion emissions and thermometric application of Er^(3+) -doped silicate glass

The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.

A novel Tb^(3+) and Eu^(3+) co-doped dual-emitting phosphate K_(3)SrBi(P_(2)O_(7))_(2) phosphor for application in FIR thermometers

Rare earth co-doped phosphor for fluorescence intensity ratio(FIR) thermometer has gained increasing attention in recent years. Herein, the novel Tb^(3+)and Eu^(3+)co-doped K_(3)SrBi(P_(2)O_(7))_(2)(KSBP) phosphate phosphors were reported. The crystal structure of the title phosphor was determined using Rietveld refinement and proved to have a three-dimensional structure. The time-resolved spectroscopy reveals that there is almost no energy transfer between Tb^(3+)and Eu^(3+). More importantly, Tb^(3+)and Eu^(3+)emissions show different thermal quenching behaviors, which claims the potential of this material for application in optical thermometer. The FIR of the typical KSBP:0.02Tb^(3+),0.04Eu^(3+)sample demonstrates a polynomial relationship as a function of temperature and the absolute and relative sensitivity are0.025 K^(-1) and 0.59%/K, respectively. In general, our study reports a novel and potential KSBP:Tb^(3+),Eu^(3+)phosphate phosphor that is promising for use in high-sensitive FIR thermometers.

Spectroscopic and temperature sensing properties of Sm^(3+) in self-activated CsLu(WO_(4))_(2) phosphors

In this research,a series of Sm^(3+) doped CsLu(WO_(4))_(2) phosphors was prepared via high temperature solid phase technique to design new red phosphors and optical thermometric materials.Their structures,morphology,band gap and luminescence properties were characterized by X-ray diffraction,scanning electron microscopy,diffuse reflection and luminescence spectra,respectively.Under UV excitation,CsLu(WO_(4))_(2) gives rise to a blue broad emission band between 350 and 700 nm,which stems from the ^(3)T_(1u)→^(1)A_(1g) transition of WO_(6)^(6-) groups.When Sm^(3+) is introduced into CsLu(WO_(4))_(2),energy transfer between WO_(6)^(6-) groups and Sm^(3+) ions takes place in CsLu(WO_(4))_(2):Sm^(3+)phosphors,and color-tunable luminescence from blue to red is realized by controlling the Sm^(3+) doping concentration.The energy transfer efficiency between WO_(6)^(6-) groups and Sm^(3+) ons was analyzed,and the energy transfer mechanism was determined to be dipole-dipole interactions.According to the temperature-dependent luminescence spectra,WO_(6)^(6-)groups and Sm^(3+)ions exhibit large discrepancy in thermal quenching rates,and thus the temperature sensing properties of CsLu(WO_(4))_(2):Sm^(3+) in the temperature range of 283-403 K were analyzed.Based on the framework of fluorescence intensity ratio theory,the basic optical thermometry parameters including absolute and relative sensitivity of CsLu(WO_(4))_(2):Sm^(3+) we re calculated and the results show that it has great potential for application in optical thermometry.

Effect of radiative loss mechanisms on FIR thermometric parameters of Nd^(3+)-doped lithium tellurite glasses

Nd^(3+)-doped tellurite glasses are promising materials for thermometers based on the fluorescence intensity ratio(FIR)technique.Nevertheless,at high Nd^(3+)concentrations,energy transfer(ET)processes such as optical reabsorption and cross-relaxation can affect the Nd^(3+)emission,which has been little explored in the literature.Therefore,the present work investigated the use of Nd^(3+)-doped tellurite glass(samples doped with Nd^(3+)at 0.2 mol%,0.5 mol%,2.0 mol%,and 4.0 mol%)in fluorescence thermometers,in the temperature range from 299 to 371 K.The results indicate a strong dependence of the FIR parameters on the Nd^(3+)concentration,due to changes in the emission band profiles caused by optical reabsorption of the Nd^(3+)emissions and cross-relaxation processes.A decrease of the relative sensitivity of the ratio^(4)F_(5/2)→^(4)I_(9/2)/^(4)F_(3/2)→^(4)I_(9/2)is observed for samples doped with higher amounts of Nd^(3+).The maximum relative sensitivity at 299 K is 3.00%/K,which is the highest value among the reported Nd^(3+)ions.

A highly sensitive multiple-mode optical thermometer designed in Eu^(2+/3+)and Li^(+)co-doped polymorphism compound LaSc_(3)(BO_(3))_(4)

Noncontact optical thermometers have attracted widespread attention,but existing problems such as single-mode and low-sensitivity thermometers still urgently need to be solved.Herein,a novel multiple-mode thermometer was designed for the polymorphism LaSc_(3)(BO_(3))_(4):Eu^(2+/3+),Li^(+).X-ray diffraction(XRD)patterns revealed a slight transition betweenα-andβ-phases with the concentrations of the dopants,which is further proved by structure refinements and first-principles calculations.The coexistence of Eu^(2+)and Eu^(3+)in the phosphors and their relative percentages were confirmed by X-ray absorption near-edge structure(XANES)spectra.Benefiting from appropriate emissions from Eu^(2+)and Eu^(3+)without obvious energy transfer and their opposite changing trends with temperatures under 307 nm excitation,a triple-mode optical thermometer is obtained for this material within the temperature range of 150–450 K.The highest sensitivities of 27.65,14.05,and 7.68%·K^(−1)are achieved based on two fluorescence intensity ratio(FIR)modes of Eu^(2+)and Eu^(3+)(5d–4f/^(5)D_(0)–^(7)F_(2,4))and the fluorescence lifetime(FL)mode of Eu^(2+),respectively.To the best of our knowledge,the former is almost the highest in Eu^(2+)and Eu^(3+)co-doped thermometers.These results indicate that this material may be used as an excellent multiple-mode optical thermometer.

Influence of dysprosium concentration on sensitivity of luminescent thermometers of phosphors Ca_(9)Tb(PO_(4))_(5)(SiO_(4))F_(2)

Tb^(3+),Dy^(3+)-co-doped Ca_(9)Tb_(x)Dy_(1-x)(PO_(4))_(5)(SiO_(4))F_(2) phosphors were prepared via high-temperature solidphase reaction method and the potential application in optical temperature measurements due to their color-tunable property was investigated in detail.The photoluminescence emission(PL) and photoluminescence excitation(PLE) spectra results show that the as-prepared phosphors exhibit both Tb^(3+) and Dy^(3+) emissions at 546 nm(^(5)D_(4)-^(7)F_(5) transition of Tb^(3+)) and 587 nm(^(4)F_(9/2)-^(6)H_(13/2) transition of Dy^(3+)) upon 376 nm excitation,respectively.In addition,the fluorescence decay analysis shows that the lifetime of the Tb3+emission rapidly decreases,which confirms the energy transfer existence between Dy^(3+) and Tb^(3+).Under 376 nm excitation,the temperature dependence of the fluorescence intensity ratios for the dualmission bands peaked at 546 and 587 nm was studied in the temperature range from 303 to 573 K.The results show that with the increase of Dy^(3+) concentration,the relative sensitivity first increases and then decreases,what’s more,the maximum relative sensitivity is 3.142×10^(-3)%/K for Ca_(9)Tb_(x)Dy_(1-x)(PO_(4))_(5)(SiO_(4))F_(2)(x=0.4).As a consequence,this preliminary study provides a novel method for exploring the novel thermo meters.

Fluorescence Determination of Artemisinin Using Tyrosinase as Catalyst and Pyronine B as Monitor

Fluorescence decrease ratio （F0/F） was applied to determination of artemisinin （qinghaosu, QHS） based on the catalytic effect of tyrosinase using tetraethyldiaminoxanthenyl chloride （pyronine B, PB） as monitor. A catalyst used commonly in the decomposition of QHS, tyrosinase, exhibited higher binding activity than hemin, which was expressed as Michaelis-Menten parameters, km, Vmax, and kcat respectively. Interaction of QHS with tyrosinase was inhibited in the presence of deactivating agents at high temperature whereas enhanced by ethanol. Under optimal conditions, a concentration of 1.4×10^-7-8.4×10^-7 mol·L^-1of QHS could be determined on the basis of fluorescence decrease ratio of PB, with a detection limit 3tr of 2.6×10^-9 mol·L^-1. The proposed method was applied to detection of the concentration of QHS in the media of plasma and urine.

Multi-site occupancies and dependent photoluminescence of Ca_(9)Mg_(1.5)(PO_(4))_(7):Eu^(2+) phosphors:A bifunctional platform for optical thermometer and plant growth lighting

Herein,we demonstrate an optical thermometer based on single Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_4)_7 phosphors,which were prepared by traditional solid-state reaction technique under a reduction atmosphere.Considerations on the bond length obtained by the crystal structure refinement and the dependent photoluminescence performances allow to assign the two distinct emission bands to Eu^(2+)ions occupied Cal-Ca3 and Mg2 sites.Moreover,the blue and red emitting bands perfectly match with the photosynthetic action spectrum,which can enhance the indoor plant photosynthesis.The optimal doping content of Eu^(2+)ions in this Ca_(9)Mg_(1.5)(PO_(4))_(7)system is 3 mol%.The corresponding concentration quenching effect is verified as dipole-dipole interaction with the critical distance of 3.315 nm.Furthermore,by exploiting the fluorescence intensity technique,the optical thermal resistance properties of Ca_(9)Mg_(1.5)(PO_4)_7:Eu^(2+)are identified based on the temperature dependent emission spectra in a range of 303-523 K.In detail,the maximum absolute and relative sensitivity S_(a)and S_(r)of Ca_9Mg_(1.5)(PO_(4))_(7):Eu^(2+)thermometer are as high as 0.637%/K and 0.3155 K^(-1),respectively.Consequently,the Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_(4))_(7)phosphors establish a bifunctional platfo rm for both optical the rmometer and plant growth lighting via multi-site occupancies.

Enzyme-free photothermally amplified fluorescent immunosorbent assay(PAFISA)for sensitive cytokine quantification

Cytokine monitoring has attracted great attention due to its significance in the diagnosis and treatment of many diseases,such as tumors,microbial infections,and immunological diseases.Enzyme-linked immunosorbent assay(ELISA)is one of the most popular methods in cytokine detection,ascribing to the lavish signal amplification methods in the ELISA platform.In addition to classical enzymes,other signal amplifiers such as fluorescent probes,artificial nano-enzymes,and photothermal reagents have been applied to reduce the detection limit and produce more sensitive ELISA kits.Due to the accumulative effect of heat,photothermal reagents are promising materials in the signal amplification of ELISA.However,the lack of efficient photothermal generation material at an aggregate scale may delay the further development of this area.In this contribution,based on an efficient organic photothermal aggregate material,an enzyme-free photothermally amplified fluorescent immunosorbent assay system consisting of an assay microfluidic chip and detecting platform was developed.The photothermal nanoparticles with highly efficient photothermal conversion by harvesting energy via excited-state intramolecular motions and enlarging molar absorptivity were successfully prepared.The detection concentration at 50 pg/mL of interleukin-2 was achieved,realizing a signal improvement of detection limits by 20-fold compared to that of previously reported photothermal ELISA.The microscopic imaging integrated with plane sweeping technology provided high spatial resolution and precision,indicating the potential of achieving high throughput profiling at the microscale.Moreover,as an alternative excitation source,light-emitting diode not only provided a more affordable and miniaturized detection system but also revealed the great feasibility of intramolecular motion-induced photothermy nanoparticles for biological analyses.

Y_(4)GeO_(8):Er^(3+),Yb^(3+) up-conversion phosphors for optical temperature sensor based on FIR technique

Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR)method complemented by detailed analysis on crystal structure,up-conversion luminescence and energy transfer from Yb^(3+)to Er^(3+).Upon 980 nm laser excitation,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors present525,547 and 659 nm emission bands assigned to the characteristic transitions of Er^(3+).Furthermore,Y_(4)GeO_(8):Er^(3+),Yb^(3+)samples show outstanding temperature sensing performances.To be specific,the minimal temperature resolution is 0.03 K(303 K),and the relative sensitivity of FIR can be up to 1.152%/K(303 K).Hence,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors can be possible candidates for thermometry devices.

Er^(3+)-Yb^(3+)-Na^(+):ZnWO_(4) phosphors for enhanced visible upconversion and temperature sensing applications

The crystal structure and surface morphology of the Er^(3+)/Yb^(3+)/Na+:ZnWO_(4) phosphors synthesized by solid state reaction method were analyzed by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) analysis.The frequency upconversion(UC) emission study in the developed phosphors was investigated by using 980 nm laser diode excitation.The effect of codoping in the Er^(3+):ZnWO_(4) phosphors on the UC emission intensity was studied.The UC emission bands that are exhibited in the blue(490 nm),green(530,552 nm),red(668 nm) and NIR(800 nm) region correspond to the ^(4)F_(7/2)→^(4)I_(15/2).^(2)H_(11/2),^(4)S_(3/2)→^(4)I_(15/2),^(4)F_(9/2)→^(4)I_(15/2) and ^(4)I9/2→^(4)I_(15/2) transitions,respectively.The temperature sensing performance of the Er^(3+)-Yb^(3+)-Na+:ZnWO_(4) phosphors was investigated based on the 2 H_(11/2)→^(4)I_(15/2) and ^(4)S_(3/2)→^(4)I_(15/2) thermally coupled transitions of the Er^(3+)ions.The photometric study was also carried out for the developed phosphors.

Up-conversion luminescence of Er^(3+)and Yb^(3+)co-doped CaBi_(2)Ta_(2)O_(9) multifunctional ferroelectrics

Er^(3+)and Yb^(3+)co-doped CaBi_(2)Ta_(2)O_(9)(CBT)-based bismuth layered-structure oxides were synthesized by a simple solid-state reaction method.Their up-conversion(UC)luminescence,dielectric and ferroelectric properties were investigated.Two strong green emission bands centered at 526 and 547nm and a weak red emission band centered at 658nm were obtained under a 980nm laser excitation at room temperature.These emission bands originated from the radiative relaxation of Er^(3+)from 2H_(11)=2,4S_(3)=2,and 4F_(9/2) levels to the ground state 4I_(15)=2,respectively.At the meantime,the fluorescence intensity ratio(FIR)variation of two green UC emissions at 526 and 547nm has been studied as a function of temperature in the range of 153–603K.The maximum sensor sensitivity obtained was 39×10^(-4)K^(-1) at 590K,which indicated that Er^(3+)=Yb^(3+)co-doped CBT ceramic is a promising candidate for applications in optical high temperature sensor.