Large Relative Sensitivity Research Articles

Ratiometric visualization fluorescence temperature sensing based on dual-lanthanide metal-organic frameworks

High-performance optical temperature sensors play an important role in various fields, and lanthanide metal-organic frameworks (Ln-MOFs) are expected to be luminescent temperature sensors due to their distinctive luminescent properties. Herein, a new three-dimensional (3D) Ln-MOF [Tb(TCA)(Phen)]·DEF (1) (H3TCA = 4,4′,4′'-nitrilotribenzoic acid, Phen = 1,10-phenanthroline, DEF= N, N-diethylformamide) is constructed with a rtl topology based on {Tb2(COO)4} secondary building units (SBUs). Meanwhile, dual-lanthanide Ln-MOFs [TbxEu1-x(TCA)(Phen)]·DEF (2-6) are also synthesized by varying the ratio of Tb3+: Eu3+ in the reaction mixture, which can be applied in practical LED applications originating from their visual luminescent color changes. Among them, 4 is an efficient ratiometric fluorescent thermometer over a wide temperature range from 283 to 393 K and has a large relative sensitivity Sr of 4.2407 % K−1 at 393 K with good repeatability. Furthermore, the emission color of 4 gradually changes from yellow (283 K) to orange-red (393 K) as temperature increases for visual colorimetric temperature measurements, which attributed to the energy transfer between Tb3+ and Eu3+ ions.

Color-tunable luminescence and temperature sensing properties of a single-phase dual-emitting La2LiSbO6:Bi3+, Sm3+ phosphor

In this article, we present a systematic research on the structure, tunable luminescence and temperature sensing properties of Bi3+, Sm3+ singly/co-doped La2LiSbO6 phosphors, which were prepared via solid state reaction method. All the X-ray diffraction (XRD) patterns of prepared samples showed very good coincidence with the pure La2LiSbO6 and the accurate lattice parameters were refined using high-quality XRD data. Under near ultraviolet excitation, the La2LiSbO6:Bi3+ phosphor exhibits a broad blue-violet band corresponding to the 3P1 →1S0 transition of Bi3+ ions, whereas the La2LiSbO6:Sm3+ phosphor exhibits characteristic luminescence properties of Sm3+ with four emission bands in the reddish-orange region. The large overlap between the emission spectrum of Bi3+ and excitation spectrum of Sm3+ leads to efficient energy transfer (ET) from Bi3+ to Sm3+ ions, which is also demonstrated by the emission spectra and decay curves of Bi3+ in La2LiSbO6:Bi3+, Sm3+ phosphors. On the basis of the Dexter and Reifsfeld's theory, the critical distance for ET between Bi3+ and Sm3+ was calculated to be 12.05 Å and the ET mechanism was determined to be a dipole-dipole interaction. Furthermore, because of the huge discrepancy between the thermal quenching rates of Bi3+ and Sm3+, the La2LiSbO6:Bi3+, Sm3+ phosphor exhibits excellent optical sensitivity to temperatures with a large relative sensitivity (Sr) of 1.48%K−1. Finally, the potential application of the La2LiSbO6:Sm3+ phosphor in indoor illumination was also evaluated according to the photoelectric parameters of the fabricated LED.

Bi3+-based luminescent thermometry in perovskite-type CaZrO3 phosphor

Based on the luminescence of Bi3+, novel temperature sensing materials CaZrO3:Bi3+ and CaZrO3:Bi3+/Sm3+ were successfully synthesized by solid-state reaction. The XRD patterns show that the synthesized materials have a pure phase of CaZrO3. The XPS results show that the Bi3+ and Sm3+ can be detected in CaZrO3:Bi3+/Sm3+. With the excitation of 318 nm, the CaZrO3:Bi3+ material shows intense temperature-dependent luminescence. The maximum relative sensitivity can be obtained at 440 K (1.78% K−1). Under the excitation of 408 nm, the CaZrO3:Sm3+ material shows the characteristic emission peaks of Sm3+. The spectral overlap between the emission spectrum of Bi3+ and the excitation spectrum of Sm3+ leads to an energy transfer from Bi3+ to Sm3+ in CaZrO3:Bi3+/Sm3+ phosphor. With the excitation of 318 nm, the emission spectrum of CaZrO3:Bi3+/Sm3+ material shows the characteristic peaks of Bi3+ and Sm3+. The fluorescence decay curves also show the evidence of the energy transfer from Bi3+ to Sm3+. The luminescence intensity ratio of Sm3+ and Bi3+ in CaZrO3:Bi3+/Sm3+ shows obvious temperature dependence. Based on the luminescence intensity ratio, a large relative sensitivity is obtained at 443 K (1.15% K−1).

Non-contact thermometry with dual-activator luminescence of Bi3+/Sm3+: YNbO4 phosphor

Based on the luminescence of Bi3+, novel temperature sensing materials YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ were successfully synthesized by solid state reaction. The XRD patterns show that the synthesized materials have a pure phase of YNbO4. With the excitation of 314 nm, the YNbO4:Bi3+ material shows intense temperature-dependent luminescence in the range of 303 K–463 K. Based on the temperature-dependent luminescence of Bi3+ in YNbO4, the maximum relative sensitivity can be obtained at 434 K (1.72% K−1). Under the excitation of 406 nm, the YNbO4:Sm3+ material shows the characteristic emission peaks of Sm3+. In YNbO4:Bi3+/Sm3+ phosphor, the large overlap between the emission spectra of Bi3+ and the excitation spectra of Sm3+ leads to a significant energy transfer from Bi3+ to Sm3+. With the excitation of 314 nm, the emission spectra of YNbO4:Bi3+/Sm3+ material shows the characteristic peaks of Bi3+ and Sm3+. The luminescence intensity ratio of Sm3+ and Bi3+ shows a strong temperature dependence. Based on the luminescence intensity ratio, a large relative sensitivity is obtained at 455 K (1.57% K−1).

An improved single probe method for sap flow measurements using finite heating duration

Because of its low cost and simple fabrication, it is easy to advocate for the single probe method as a method of choice in sap flow studies. An improved single probe method with finite heating duration (F-SPHP) is verified both in cut stem segments and in the field using mature beech (Fagus sylvatica L.) trees. The F-SPHP method is based on an analytical solution of the partial differential equation for combined heat conduction and convection, which shows large relative sensitivity to thermal conductivity (K). The F-SPHP method is able to measure sap flux densities (SFD) between 2 and 36 cm3 cm−2 h−1 (heat pulse velocity (Vh): 3–60 cm h−1) in the cut stem segment experiment. This is an improvement compared to the instantaneous single probe heat pulse (I-SPHP) method which cannot accurately measure low (Vh < 20 cm h−1) sap flow. Sapflow+ (a four-needle heat pulse method) is used for field validation, and when compared with gravimetric measurements, slopes of 0.853 and 0.730 are obtained for F-SPHP and Sapflow+, respectively. Patterns measured with F-SPHP and Sapflow+ in mature beech trees in the forest are similar at all measurement positions and temperature correction is needed for both methods when natural temperature gradients are steep. Compared with multi-probe methods, the single probe method with finite heating duration has the advantage of causing less damage to conductive tissue.

Results at Recruitment From a Randomized Controlled Trial Comparing Human Papillomavirus Testing Alone With Conventional Cytology as the Primary Cervical Cancer Screening Test

In the first recruitment phase of a randomized trial of cervical cancer screening methods (New Technologies for Cervical Cancer Screening [NTCC] study), we compared screening with conventional cytology with screening by human papillomavirus (HPV) testing in combination with liquid-based cytology. HPV-positive women were directly referred to colposcopy if aged 35 or older; if younger, they were retested after 1 year. In the second recruitment phase of NTCC, we randomly assigned women to conventional cytology (n = 24,661) with referral to colposcopy if cytology indicated atypical squamous cells of undetermined significance or more severe abnormality or to testing for high-risk HPV DNA alone by Hybrid Capture 2 (n = 24,535) with referral to colposcopy if the test was positive at a concentration of HPV DNA 1 pg/mL or greater. For the main endpoint of the study, histologic detection of cervical intraepithelial neoplasia of grade 2 or more (CIN2+), we calculated and compared sensitivity and positive predictive value (PPV) of the two screening methods using HPV DNA cutoffs of 1 pg/mL and 2 pg/mL. All statistical tests were two-sided. For women aged 35-60 years, the relative sensitivity of HPV testing for detection of CIN2+ at a cutoff of 1 pg/mL vs conventional cytology was 1.92 (95% CI = 1.28 to 2.87) and the relative PPV was 0.80 (95% CI = 0.55 to 1.18). At a cutoff of 2 pg/mL HPV DNA, the relative sensitivity was 1.81 (95% CI = 1.20 to 2.72) and the relative PPV was 0.99 (95% CI = 0.67 to 1.46). In this age group, there was no evidence of heterogeneity between study phases. Among women aged 25-34 years, the relative sensitivity for detection of CIN2+ of HPV testing at a cutoff of 1 pg/mL vs cytology was 3.50 (95% CI = 2.11 to 5.82), statistically significantly larger (P = .019) than that observed in phase 1 at this age (1.58; 95% CI = 1.03 to 2.44). For women aged 35-60 years, HPV testing with a cutoff of 2 pg/mL achieves a substantial gain in sensitivity over cytology with only a small reduction in PPV. Among women aged 25-34 years, the large relative sensitivity of HPV testing compared with conventional cytology and the difference between relative sensitivity during phases 1 and 2 suggests that there is frequent regression of CIN2+ that are detected by direct referral of younger HPV-positive women to colposcopy. Thus, triage test or repeat testing is needed if HPV is to be used for primary testing in this context.

Can Prostate-Specific Antigen and Prostate-Specific Antigen Velocity Be Used for Prostate Cancer Screening in Men Older Than 70 Years?

We evaluated the lower threshold of prostate-specific antigen (PSA) and prostate-specific antigen velocity (PSAV) in a population of men over 70 years of age. Between January 1988 and December 2005, 4038 men over 70 years of age including 605 African-American (AA) men and 3433 non-AA men from the Duke Prostate Center Outcomes database had determination of serum PSA and PSAV. We used receiver operating characteristic (ROC) curves to display the data graphically. The median age for all men on the study was 75 years. The area under the curve (AUC) for PSA in AA men and non-AA men was 0.84 and 0.76, respectively. For PSAV the AUC was 0.71 versus 0.54, respectively. The largest relative sensitivity and specificity in AA men was achieved at the established PSA cut-point of 4.0 ng/mL: 85% and 71%, respectively. The best cut-point in non-AA men was 3.4 ng/mL, which resulted in a sensitivity and specificity of 72% and 73%, respectively. The AUC of ROC curves within various age subgroups tends to be stable regardless of how the ages are grouped. In a multivariate logistic regression model age, PSA and PSAV were significant predictors of cancer status in the AA subset. Age and PSA were significant predictors in the non-AA subset. The AUC of ROC curves within various age subgroups tends to be stable; therefore, we are led to believe that a PSA or PSAV cutoff for safely commending discontinuation of PCa screening is not apparent from these data.