Doped NaYF4 Research Articles

A dual-ratiometric strategy to design the NIR-IIb reference-based activatable nanoprobe for accurate nitric oxide detection

Fluorescence imaging offers a real-time, convenient method for detection nitric oxide (NO) in vivo, especially using the near-infrared IIb (NIR-IIb, 1500–1700 nm) region. However, traditional single-ratiometric fluorescent probes for NO detection suffer from signal distortion due to inherent limitations such as signal crosstalk and component separation. Herein, we proposed a dual-ratiometric strategy to ensure detection accuracy. The detection result was considered to be reliable upon the auxiliary ratio and practical ratio exhibiting a synchronous change. Based on this strategy, we fabricated a NO-responsive probe, comprising a conjugated polymer P-NH2 and a rare-earth doped nanocrystal NaYF4:Yb,Er,Ce@NaYF4:Yb,Nd@NaYF4. When interaction with NO, the probe generated two ratiometric signals: FNIR-I/FNIR-IIb and FNIR-II’/FNIR-IIb (NIR-I, 700–900 nm; NIR-II’, 1000–1400 nm), where the latter acted as the practical ratio for its better imaging clarity. With an acetaminophen-induced liver injury model, the probe demonstrated the potential for precise ratiometric imaging of NO distribution in vivo. Particularly, ratio imaging revealed the intricate vascular structure of the abdomen, demonstrating the significant advantages of the NIR-IIb region. Our study offers an effective approach to reduce detection errors in the bioimaging applications and provides a powerful tool for basic biomedical research.

Effect of Pr3+ concentration in luminescence properties & upconversion mechanism of triple doped NaYF4: Yb3+, Er3+, Pr3+

Lanthanide-doped fluoride nanocrystals (NCs) exhibit excellent optical features, including upconversion and downconversion luminescence (UCL and DCL), that can be utilized in a variety of applications. In this study, we have successfully demonstrated the photoluminescence behavior of triple-doped NaYF4: Yb3+, Er3+, Pr3+ NCs in the Vis-NIR region. Herein, highly monodisperse hexagonal phase NaYF4: Yb0.2, Er0.02, Prx nanocrystals in various Pr3+ (x = 0, 0.1, 0.5, and 1 mol %) concentration with ∼22 nm diameter synthesized by thermal decomposition technique. The photoluminescence studies for all samples were performed under 980 nm laser excitation. The luminescence intensity of Er3+ including blue (407 nm), green (520 and 540 nm), red (654 nm), and near-infrared (845 nm and 1530 nm) emissions was significantly quenched and Pr3+ emission intensity at 1290 nm (Pr3+:1G4→3H5) changes irregularly upon doping with Pr3+ ions. Furthermore, we performed the excitation power dependence and decay time analysis to investigate the energy transfer and upconversion mechanisms of samples. These findings indicate that the presence of praseodymium strongly reduces emission intensities due to abundant cross-relaxation channels. In addition, particle size is an efficient factor, shedding light on the influence of Pr3+ on the energy transfer and upconversion mechanisms of the fluorides.

Ho3+ doped low-phonon single crystals and chalcogenide glasses for mid-IR source application

A comparative study was conducted to investigate the 3.9 µm mid-IR emission properties of Ho3+ doped NaYF4 and CsCdCl3 crystals as well as Ho3+ doped Ga2Ge5S13 glass. Following optical excitation at ∼890 nm, all the studied materials exhibited broad mid-IR emissions centered at ∼3.9 µm at room temperature. The mid-IR emission at 3.9 µm, originating from the 5I5 → 5I6 transition, showed long emission lifetime values of ∼16.5 ms and ∼1.61 ms for Ho3+ doped CsCdCl3 crystal and Ga2Ge5S13 glass, respectively. Conversely, the Ho3+ doped NaYF4 crystal exhibited a relatively short lifetime of ∼120 µs. Temperature dependent decay time measurements were performed for the 5I5 excited state for all three samples. The results showed that the emission lifetimes of Ho3+:CsCdCl3 and Ho3+:Ga2Ge5S13 were nearly temperature independent over the range studied, while significant emission quenching of the 5I5 level was observed in Ho3+:NaYF4. The temperature dependence of the multi-phonon relaxation rate for 3.9 µm mid-IR emission in Ho3+:NaYF4 crystal was determined. The room temperature stimulated emission cross-sections for all three samples were calculated using the Füchtbauer-Landenburg equation. Furthermore, the results of Judd-Ofelt analysis are presented and discussed.

Preparation of rare-earth doped NaYF4 luminescent nanoparticles by a high-energy ball milling process

An optimized scalable production of single-phase rare-earth doped β-NaYF4 nanoparticles is developed by the high-energy ball milling. This approach opens up prospects for the photoluminescent nanomaterials fabrication for biotechnology and photonics.

An innovative approach to photolithography for optical recording of high-resolution two-dimensional structures in a negative SU8 photoresist by activation of up-conversion luminescence in Yb[formula omitted] and Tm[formula omitted] doped NaYF[formula omitted] nanoparticles

In this work, we demonstrate the success of an innovative approach to photolithographic recording of high-resolution 2D structures in thin films of hybrid inorganic nanoparticles/photoresist systems. This is done by utilising Yb3+, Tm3+ up-conversion luminescence in core–shell (β-NaYF4:Yb3+, Tm3+/ β-NaYF4)-structured nanoparticles (33.9 nm in size) mixed into a negative photoresist SU8. This approach is a promising alternative compared to traditional optical lithography performed by i-line UV radiation through a surface. Specially designed core–shell-structured nanoparticles were synthetised to emit Tm3+-characteristic up-conversion luminescence bands in the UV spectral region at 345 and 361 nm, and in the blue spectral region at 450 and 476 nm under IR excitation at 976 nm. The exposed elliptically shaped uniform structure, with dimensions of ∼160 ×320μm, was recorded in a ∼500 nm thin photosensitive layer by 1–5 min long infrared exposure when core–shell nanoparticles doped with Yb3+ and Tm3+ ions were mixed into negative photoresist SU8. Such hybrid systems of organic chromophores/UCNP/SU8 are highly prospective for the fabrication of various types of microstructures without damaging the light-sensitive organic compound, which is required in medicine (microsurgery, laboratory on a chip, etc.), telecommunications, military, sensor technologies and a wide range of photonic applications, e.g. for the fabrication of micro disk resonators used as active media in organic solid-state lasers.

Quantitatively identifying the upconversion luminescence mechanisms of Er3+:NaYF4 nanocrystals in aluminosilicate glass ceramics under femtosecond laser field

Upconversion luminescence of lanthanide ion doped nanocrystals under ultrashort laser pulse excitation can find significant applications in areas like super-resolution nonlinear microscopic imaging and attracts increasing attention. Though major excitation mechanisms, such as excited state absorption (ESA), energy transfer upconversion (ETU) and multi-photon absorption (MPA), have been analyzed and discussed intensively, quantitative differentiation of their respective contributions with convincing experimental proof has seldom been reported however. Here we report experimental demonstration of a simple but effective way to quantitatively identify simultaneous MPA from other mechanisms like ESA and ETU involved in the Er3+ doped NaYF4 nanocrystals in aluminosilicate glass ceramics under femtosecond laser field excitation. Comparative studies using laser pulses of the same spectral bandwidth but different time duration or repetition rate are performed and convincing experimental evidences for their respective contribution weights are obtained. The dependence of the MPA excitation efficiency on the spectral bandwidth of the femtosecond laser pulse is also explored for maximizing the upconversion luminescence yield. And predictions from a theoretical model agree well with experimental observations.

The influence of Ce3+ codoping on upconversion in nanocrystalline NaYF4:Yb3+,Tm3+

Usually, to obtain multicolor upconversion in lanthanides, materials with different codopants, different size, chemical composition or compositional architecture are required. However, designing a material whose emission color can be tuned in-situ by an external stimulus, such as temperature, excitation pulse duration or photoexcitation density, is of great interest for many applications, but still remains a challenge. The possible solution for this issue can be achieved by intentional codoping the luminescent materials with optically active ions which can disturb or compete with other energy transfer processes, and in consequence lead to changes in relative emission intensity, thus the dominant emission color. Here we synthesized and investigated colloidal luminescent Yb3+ and Tm3+ doped NaYF4 nanoparticles which were codoped with optically active Ce3+ ions, whose relative emission intensity ratios between 1D2→3F4 (at 450 nm), 1G4→3H6 (at 475 nm), 1G4→3F4 (at 650 nm), and 3H4→3H6 (at 800 nm) were significantly dependent from external stimulus – namely temperature and/or excitation pulse length. Our results shows two fold increase in 450/800, 470/800 and 650/800 luminescence intensity bands ratios (LIR) only after incorporation of Ce3+ ions to the material, and even three-fold increase in those LIR after changing the excitation conditions (i.e. pulse width). Moreover, temperature dependent luminescence properties revealed relative sensitivity of 4%/K for the 450/800 and 470/800 bands ratio and almost 5.5%/K for the 650/800 band ratio close to 0 °C. By switching to physiological range of temperatures, the thermal sensitivity decreased to around 2%/K for the 450/800 and 470/800 bands ratio and to over 2.5%/K for 650/800 bands ratio, which should be considered as significant values and suitable for temperature sensing in practical applications. It is worth noting that the thermal sensitivity values can be further enhanced by applying different excitation pulse width. The proposed materials allows to tune its emissions as well as thermal properties by changing the dopant concentration or more importantly also in situ, through excitation scheme modifications.

Yb- and Er concentration dependence of the upconversion luminescence of highly doped NaYF4:Yb,Er/NaYF4:Lu core/shell nanocrystals prepared by a water-free synthesis

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion (UC) nanocrystals (UCNC) like NaYF4:Yb,Er and first strategies were reported to reduce concentration quenching in highly doped UCNC. UC luminescence (UCL) is, however, controlled not only by dopant concentration, yet by an interplay of different parameters including size, crystal and shell quality, and excitation power density (P). Thus, identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative spectroscopy. Here, we quantify the dopant concentration dependence of the UCL quantum yield (ΦUC) of solid NaYF4:Yb,Er/NaYF4:Lu upconversion core/shell nanocrystals of varying Yb3+ and Er3+ concentrations (Yb3+ series: 20%–98% Yb3+; 2% Er3+; Er3+ series: 60% Yb3+; 2%–40% Er3+). To circumvent other luminescence quenching processes, an elaborate synthesis yielding OH-free UCNC with record ΦUC of ∼9% and ∼25 nm core particles with a thick surface shell were used. High Yb3+ concentrations barely reduce ΦUC from ∼9% (20% Yb3+) to ∼7% (98% Yb3+) for an Er3+ concentration of 2%, thereby allowing to strongly increase the particle absorption cross section and UCNC brightness. Although an increased Er3+ concentration reduces ΦUC from ∼7% (2% Er3+) to 1% (40%) for 60% Yb3+. Nevertheless, at very high P (> 1 MW/cm2) used for microscopic studies, highly Er3+-doped UCNC display a high brightness because of reduced saturation. These findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

Investigation of thermoluminescence and photoluminescence properties of Tb3+, Eu3+, and Dy3+ doped NaYF4 phosphors for dosimetric applications.

Hexagonal phase sodium yttrium fluoride activated with lanthanide ions; Tb3+, Eu3+ and Dy3+ doped NaYF4 phosphors were synthesized using a simplistic hydrothermal method. The photoluminescence studies demonstrated green, red and blue emission lines corresponding to 5D4 → 7FJ (J = 6, 5, 4, 3), 5D0 → 7FJ (J = 1, 2 and 4) and 4F9/2 to 6HJ (J = 15/2 and 13/2) transitions, which are characteristic of Tb3+, Eu3+ and Dy3+ ions, respectively. The as-synthesized samples were subjected to annealing at varying temperatures from 500 °C to 800 °C primarily for the optimization of the thermoluminescence glow curve. Meanwhile, we studied the influence of thermal annealing treatment on the crystal phase, morphological features, and photoluminescence properties of the phosphors. The spherical-like morphology of NaYF4:Tb3+ phosphor changed to micro block-like structures and the hexagonal phase of NaYF4 transforms into a cubic phase at a higher annealing temperature of ∼800 °C. The photoluminescence emission intensity also varied at different annealing temperatures. The systematic study using different dopants and annealing temperatures was carried out to accomplish efficient thermoluminescence (TL) properties. The most suitable TL dosimetric glow peak was attained for NaYF4:0.5%Tb3+ phosphor, which was annealed at a temperature of 800 °C, located at 194 °C. The NaYF4:Tb3+ phosphor exhibited TL response fairly linear in the dose range from 1 kGy to 25 kGy of gamma radiation. The phosphor showed TL response at higher doses, which stipulates that the NaYF4:Tb3+ is reasonably well suitable for high dose measurements and respective applications. The phosphor exhibited negligible fading and good reproducibility features. Trap-level analysis and experimental determination of activation energy were performed using the Tm-Tstop technique and initial rise method (IRM). The trapping parameters of the TL glow curve, such as activation energy (E), order of kinetics (b), and frequency factor (s) were estimated by Chen's glow peak shape (PS) method and glow curve deconvolution (GCD) method. The trapping parameters obtained using the IRM, PS and GCD methods are in good accordance with each other. Henceforth, along with efficient photoluminescence properties, the NaYF4:Tb3+ phosphor exhibited favorable thermoluminescence dosimetric properties. Consequently, this study provides new opportunities for utilizing these phosphors in the area of radiation dosimetry applications such as environmental and food monitoring, space dosimetry etc.

Concentration effects of fluorescence quenching and optical transition properties of Dy3+ doped NaYF4 phosphor

Doping concentration is an important factor influencing the optical and spectroscopic properties of rare earth doped luminescence materials. In this work, the influences of Dy3+ concentration on fluorescence intensity and optical transition properties were studied. Huang’s and Uitert’s models were compared and used in discovering the fluorescence intensity quenching mechanism of Dy3+ in NaYF4 phosphors, and it was found that from these two models the fluorescence intensity quenching mechanism can be well deduced though the application manners of the models are different. The dependence of optical transition properties on Dy3+ doping concentration was studied in depth. It was found that with increasing Dy3+ concentration the Ω2 value increases and the Ω4 value decreases monotonically, nevertheless the Ω6 value changes slightly. Moreover, the magnitude sequence of the Judd-Ofelt parameters changes from Ω4>Ω6>Ω2 to Ω2>Ω6>Ω4 when the concentrations of Dy3+ increases. Furthermore, it was found that the internal quantum efficiency of 4F9/2 decreases with increasing Dy3+ concentration.

Spectroscopic properties and dynamic analysis of three-photon quantum-cutting luminescence in Er doped NaYF4 nanoparticles

Spectroscopic properties and dynamic analysis play a significant role during the design and development of novel luminescent materials. In this work, Er3+ doped NaYF4 nanoparticles were successfully synthesized by coprecipitation method. The absorption spectrum, fluorescence spectra, and decay curves were measured at room temperature. The spectroscopic properties, including the radiative and nonradiative transition probability, fluorescent branch ratio, cross-relaxation rate and the fluorescence lifetime, were calculated based on the Judd-Ofelt theory. Furthermore, the rate equation models were established to analyze the dynamic processes of three-photon near-infrared quantum cutting luminescence. The time-dependent population densities of excited levels of Er3+ ions were simulated and the theoretical quantum efficiency was calculated to be 252.40%, which is consistent with our experimental results.

Enhanced Visible/NIR driven catalytic activity in presence of neodymium (Nd3+), for Yb3+ and Tm3+ doped NaYF4 nanoparticles

Removal of organic dye-based impurities from water has been achieved traditionally by the use of photocatalysts. ZnO is a commonly used photocatalyst that works when irradiated by UV irradiation. Since the UV fraction in a solar spectrum is very small, there is a scope of utilizing the near-infrared and visible spectrum for the process of dye degradation. We synthesized a novel tri-dopant upconversion nanoparticle (NaYF4:Yb,Tm,Nd) system using a simplified microwave-assisted technique and combined it with ZnO particles for methylene blue dye degradation studies. We examined the role of neodymium (Nd3+) dopant on the efficiency of dye degradation when illuminated under an inexpensive tungsten halogen lamp source. X-ray diffraction studies revealed that the presence of Nd3+ in the crystal lattice leads to a reduction in the particle size due to shrinkage in the crystallite size. The presence of Nd3+ in upconversion nanoparticles revealed several characteristic absorption bands from 520 nm to 870 nm along with the characteristic 980 nm corresponding to (ytterbium) Yb3+. The power-dependent study at 980 nm confirmed the multi-photon process of upconversion. The degradation efficiency revealed up to 92% degradation for 5 mg L−1 of dye. The degradation efficiency of upconversion nanoparticles and ZnO system in the presence of Nd3+ was 72% and in the absence of Nd3+ was 58%, for a dye concentration of 10 mg L−1. The dye degradation rate constant was higher for NaYF4:Yb,Tm,Nd and ZnO system (0.0041 min−1) compared to NaYF4:Yb,Tm, and ZnO set (0.0029 min−1). Thus, the presence of Nd3+ widens the absorption spectra of UCNP in both the visible and near-infrared (NIR) range.

Chelating agent and substrate effect on hydrothermal growth of Yb3+/Er3+ doped NaYf4 film

We report simultaneous crystal growth and deposition of upconverting Yb3+/Er3+ doped NaYF4 film (UCF) on conducting and non-conducting substrates by one-step hydrothermal method. The characteristics such as film topography, morphology, crystallographic phase and upconverting luminescence intensity were found to depend both on the chelating agent and nature of the substrate. The characteristics of the prepared films varied interestingly when either the chelating agent or the substrate was changed. The upconversion emission intensities were found to increase with decreasing film roughness. Further, current investigation demonstrated that the NaYF4 films deposited using EDTA or DTPA chelating agents on ITO substrate and EGTA chelating agent on PG substrate were more uniform and resulted in greater upconverted emission intensities. We envision plausible use of current technology in the development of affordable optical platforms for several optoelectronic applications.

Radiative transition properties of Yb3+ in Er3+/Yb3+ co-doped NaYF4 phosphor

Usually, it is difficult to quantitatively express the optical transition properties of Yb 3+ in powdered samples owing to the difficulty in measuring the absolute absorption spectra. In this work, we developed an approach for confirming the absorption and emission cross section spectra and the radiative transition rates for the absorption and emission transitions between 2 F 7/2 and 2 F 5/2 states of Yb 3+ . The proposed approach was examined for Yb 3+ in Er 3+ /Yb 3+ co-doped NaYF 4 powders. The absorption cross section for 2 F 7/2 → 2 F 5/2 transition and emission cross section for 2 F 5/2 → 2 F 7/2 transition of Yb 3+ in NaYF 4 :Er 3+ /Yb 3+ were confirmed. Meanwhile, the transition rates for the absorption and emission transitions were also calculated. A route for calculating the radiative transition rate, absorption and emission cross sections of Yb 3+ in powdered samples is proposed. Furthermore, the radiative transition properties of Yb 3+ in NaYF 4 :Er 3+ /Yb 3+ phosphor derived from an auto-combustion-assisted fluoridation was studied via our proposed route. • NaYF 4 : Er 3+ and NaYF 4 : Er 3+ /Yb 3+ phosphors were prepared via an auto-combustion assisted solid-state reaction. • A new calculation method of radiation transition rates of Yb 3+ was proposed and used for Er 3+ /Yb 3+ co-doped NaYF 4 powders. • The absorption cross section spectra of Er 3+ /Yb 3+ co-doped NaYF 4 and Er 3+ doped NaYF 4 powders were confirmed. • The absorption and emission cross sections of Yb 3+ in NaYF 4 were derived. • The transition rates of Yb 3+ for the absorption ( 2 F 7/2 → 2 F 5/2 ) and emission ( 2 F 5/2 → 2 F 7/2 ) transitions were calculated.

Synthesis and Characterization of Yttrium based Luminescent Materials

NaYF4 is well known and most promising upconversion yttrium based fluoride phosphor till date. Fluoride synthesis is rather tricky due to their peculiar physico-chemical properties. Fluorides are highly susceptible to hydrolysis. This is detrimental to the luminescence. Conventional method for preparing complex fluoride compounds is solid state reaction which is a tedious task. In recent years, many new methods such as wet chemical synthesis have been suggested for these novel materials. These new syntheses provide more milder and efficient ways of materials preparation. Here, preparation of two luminescent hosts NaYF4 and KYF4 was attempted via Wet-Chemical synthesis. Among these, NaYF4 could be successfully prepared, whereas synthesis of KYF4 was partially successful. Formation of these compounds was confirmed by various measurements. Photoluminescence was obtained for Ce3+ doped NaYF4.

A Short Review on Rare Earth Doped NaYF4 Upconverted Nanomaterials for Solar Cell Applications

The enhancement of upconversion luminescence (UCL) of rare earth (RE) doped upconversion nanomaterials which facilitates anti-Stokes emission is particularly important and urgently required for a broad range of applications. The fascinating properties such as anti-Stokes shifts, long life times and sharp emissions exhibits potential application in various areas. The UC is one of the exciting processes in the RE ions in which one can get the emission of high energy ultra-violet (UV) and visible (Vis) photons with the help of low energy near infrared (NIR) photons. In this mini review, we have discussed fundamental concepts of NaYF4 host for UC emission. The NaYF4 host has been selected due to its low phonon energy and composition stability. We have also demonstrated that the introduction of core shell and plasmonic nanostructure which has a critical effect on UCL. The recent advances in plasmon-enhanced UCL in RE doped NaYF4 are also noted. Finally, the recent solar cell applications of RE doped NaYF4 nanocomposite phosphor materials are introduced

Femtosecond laser induced cross relaxation in Er3+ doped NaYF4 glass ceramic

Cross relaxation (CR) plays a significant role in the luminescence of rare-earth ion doped materials. It is generally considered as a major cause of concentration quenching in bulky materials and has been intentionally adopted in selectively tuning the color output. In this work, we combine streak camera with spectrometer to investigate the CR processes in Er3+ doped NaYF4 glass ceramic under a 400 nm femtosecond laser field. This combination technique incorporates the advantages of both the streak camera with high time-resolution and the spectrometer with good wavelength-resolution, and can provide the luminescence information in both the temporal and spectral dimensions. A new CR process is experimentally observed in the higher doping concentration, and its excitation mechanism is justified by comparing the luminescence lifetimes and intensities in low and high doping concentrations. This study will contribute to a better understanding of the luminescence mechanisms in the rare earth ion doped materials and its color output tuning.

Judd-Ofelt parametrization from emission spectra: The case study of the Eu3+ 5D1 emitting level

Traditional applications of the Judd-Ofelt (JO) theory to the analysis of the Eu3+ optical spectra make use of the emission transitions originating from the 5D0 manifold. In the present paper, we report an alternative method of evaluating the JO intensity parameters from the Eu3+ emission spectra based on the 5D1 → 7F0,1 transitions. The reduced matrix elements of the unit tensor operators are re-calculated for the 5D0,1,2 → 7F0,1,…,6 Eu3+ transitions in the intermediate coupling approximation using the average electrostatic and spin-orbit coupling parameters. The suggested method was tested by analyzing the emission spectra of the Eu3+ doped GdAlO3, LaF3, NaYF4, Y2O3, ZrO2, YNbO4, ZBLA and PIGLZ hosts. It is shown that the developed method is more accurate for the hosts with relatively high 5D1 level population, which emphasizes its high potential and applicability. In addition to the JO analysis, the CIE chromaticity coordinates are calculated for the investigated spectra.

Real-Time Tracking of Yb3+, Tm3+ Doped NaYF4 Nanoparticles in Living Cancer Cells

Real-Time Tracking of Yb3+, Tm3+ Doped NaYF4 Nanoparticles in Living Cancer Cells

Spectroscopic exploration of upconversion luminescence behavior of rare earth-doped single-particle micro/nanocrystals

In recent years, rare earth-doped upconversion (UC) micro/nanocrystals are useful for many applications, especially in biology because of their unique luminescent properties and specific geometry. The luminescence efficiency of lanthanide-doped UC nanoparticles is of particular importance for their applications. However, the unsatisfactory UC efficiency is still one of the main hurdles. In the present article, a series of Yb3+/Er3+ doped NaYF4 micro/nanoparticles with different ratios of length to diameter are successfully synthesized by a facile hydrothermal route. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX) analyses, photoluminescence spectra, and the dynamic process of the luminescence are used to characterize the samples. The intrinsic structural feature of fluoride, the solution pH value, and organic additive Cit3- account for the ultimate shape evolution of the final products. The ratio of length to diameter of NaYF4 microrod can be tuned only by varying the value of pH or the amount of an organic additive (Cit3-). The UC characteristics of a single NaYF4:Yb3+/Er3+ microrod obtained by tuning the value of pH or the amount of Cit3- are investigated by laser confocal microscopy with a 980 nm laser. The two series of codoped fluoride crystals both exhibit the characteristic UC luminescence from Er3+ ions and display the rich luminescence patterns in space. The UC luminescence from a single NaYF4:Yb3+/Er3+ microrod obtained by tuning the value of pH is brighter than that from a single NaYF4:Yb3+/Er3+ microrod with the same size obtained by tuning the amount of Cit3-. The EDX analysis indicates that the number of Na+ defects depends on the specific synthesis conditions of the sample. The Na+ defects of samples obtained by tuning the values of pH are lower than those of samples with the same size obtained by tuning the amount of Cit3-. It conduces to reducing Na+ defects at lower pH value. The parameters of the luminescence kinetics are found to be unambiguously dependent on the size of sample, which relates to higher energy phonon of surface and Na+ defects. The mechanism of luminescence enhancement by pH controlling is explored, and a mechanism based on the reduced intrinsic defects of Na+ is proposed. The investigation not only enriches the controllable synthesis approach of fluoride micro/nanomaterials, but also indicates the potential applications of rare earth materials with a rich luminescence pattern in the photonic devices and anti-counterfeiting devices.