Double-excited states of charge transfer band and 4f-4f in single-phase K_(3)Gd(VO_(4))_(2):Tb^(3+)/Sm^(3+) phosphors with superior sensing sensitivity for potential luminescent thermometers

Temperature is one of the fundamental parameters for thermodynamics and its accurate detection is necessary.The novel strategy of luminescent materials based on the fluorescence intensity ratio technique has been promised for thermometers in more practical environments to overcome the drawbacks of conventional thermometers in recent.Herein,the novel single-phase K_(3) Gd(VO_(4))_(2):Tb^(3+)/Sm^(3+) phosphors were successfully prepared,and the ~4 G_(5/2)→ ~6 H9/2(Sm^(3+)) and ~5 D_(4) → ~7 F_(5)(Tb^(3+)) transitions could be promised for luminescent thermometers.Besides,under the double-excited states of charge transfer band(CTB,317 nm) and 4 f-4 f(478 nm) excitations,the K_(3) Gd(VO_(4))_(2):Tb^(3+)/Sm^(3+) phosphors exhibited different concentration quenching mechanisms in energy transfer processes and also showed superior absolute sensing sensitivity(S_a) and relative sensing sensitivity(S_r).Especially,the maximum S_a and S_r values reached up to 0.568 K^(-1) and 11.24% K^(-1),respectively and the temperature resolution of the KGV:0.2 Tb^(3+)/0.01 Sm^(3+)phosphor was higher than 0.004 K under the excitation wavelength of CTB(317 nm),indicating that the double-excited states in the single-phase KGV:Tb^(3+)/Sm^(3+) phosphors with superior sensing sensitivity could be a novel candidate for potential optical thermometers.

Metal-free Optical Pressure Sensor with High Sensitivity and Extensive Range

Pressure monitoring of a transformer oil tank can grasp the pressure change process caused by gas production when severe internal defects occur and take timely measures to ensure the safe operation of the transformer.Existing pressure sensors generally use metal encapsulation or have an air cavity structure,threatening the transformer’s insulation if it is directly used inside the transformer.To this end,this paper proposes a method for developing a high-sensitivity,large-range,and metallizationfree optical pressure sensing device with temperature compensation.Fiber grating is encapsulated by fluorosilicone rubber and supplemented by an epoxy resin shielding shell on the outside.At the same time,a double-grating vertical arrangement is adopted to improve pressure measurement sensitivity,further avoiding the influence of temperature rise caused by a defect of the transformer on the measurement result of the sensor.In addition,by optimizing the geometric structure of the internal sensitizing element,pre-stretching length of the fiber grating,gap distance,and other parameters,probe size can be reduced while ensuring the sensor’s performance.Results show the proposed method can meet the requirements of sensor fabrication with different sensitivities and ranges,and to a certain extent,both high sensitivity and extensive ranges can be taken into account.The sensitivity of the fabricated prototype is 15 pm/kPa,and the range is about 0.2 MPa.At the same time,the metal-free feature of the sensor makes it suitable for use in various oil-immersed power equipment.It records oil pressure changes caused by oil discharge breakdown,making it sensitive to small pressure changes in early failures.

Pillar[5]arene and Azine Derivative Assembly Improved Dual-Channel Detection of CN-

The cyanide anion(CN^(–))is known to be one of the most toxic anions.Therefore,there is an urgent need to develop a reliable,sensitive,selective,rapid and effective method for the detection of CN^(–).Here,a self-assembly strategy based on pillar[5]arene P5 and azine derivative AZ was used to construct supramolecular sensors,and it was found that the detection effect of CN^(–)was significantly improved by the assembly strategy.The sensitivity of the assembled sensor P5-AZ to CN^(–)is more than 10 times higher than that of AZ.The detect mechanism was further investigated by theoretical calculations and 1H NMR.The results showed that AZ detects CN–by a deprotonation process with fluorescence enhancement,while P5-AZ improves the sensitivity of CN^(–)recognition through hydrogen bonding,anion-πand anion-dipole interactions,as well as the strong bonding ability of the assembly.Supramolecular assembly P5-AZ has the advantages of low toxicity,high sensitivity,and more importantly,it provides a method to detect CN^(–)sensitivity in the aqueous phase and organisms by host-guest assembly.

Label-free Detection of Biotin Using Nanoporous TiO2/DNA Thin-film Coated Wavelength Interrogated Surface Plasmon Resonance Sensors

The sensing sensitivity of the wavelength interrogated surface plasmon resonance（WISPR） biosensor could be improved by self-assembly of nanoporous thin-film of TiO2 nanoparticles/DNA（TiO2/DNA）n（n is the number of bilayer） on wavelength interrogated surface plasmon resonance（WISPR） chips.The growth behavior and surface structure of the nanoporous thin-film were investigated by UV-Vis spectroscopy and scanning electron microscopy,respectively.The home-made WISPR sensor with Krestchmann configuration consisted of a tungsten-halogen lamp as a photon source and a CCD camera as the detector.After the deposition of （DNA/TiO2）n thin film on WISPR chips,the resonance peak of the reflection spectra appeared in air.With the increases of n,the resonance wavelength gradually red shifted,which is consistent with the simulated results.After the optimization of the porous film,the WISPR biosensor was utilized to detect low-molecular-weight analytes,such as biotin.The result demonstrates that the sensitivity of [poly（styrene sulfonate）/polyally lamine hydrochlorides]5（PSS/PAH）5 could be 4 times higher than that of polyelectrolyte multilayer modified WISPR sensor.

In situ Molecular Self-assembly and Sensitive Label-free Detection of Streptavidin via a Wavelength Interrogated Surface Plasmon Resonance Sensor

The sensing sensitivity of wavelength interrogated surface plasmon resonance（WISPR） biosensor is improved by self-assembly of polyelectrolyte multilayer（PEM） film of poly（allylamine hydrochloride）（PAH）/ poly（sodium-p-styrenesulfonate）（PSS） on the Au film coated glass chip via the layer-by-layer（LBL） technique. The home-made WISPR with Krestchmann configuration consists of a tungsten-halogen lamp as a photon source and a charge coupled device（CCD） camera as the detector. The influence of PEM film thickness on the optical properties of WISPR biosensors was investigated theoretically and experimentally. In order to achieve higher sensing sensitivity, the PEM film thickness has to be designed as ca.14 nm at an Au layer thickness of 50 nm and an incidental angle of 11.8°. Furthermore, the PEM coated WISPR biosensor can serve as highly sensitive biosensor, in which the biotin-streptavidin is used as bioconjugate pair. After deposition of the PEM film of （biotin/PAH）（PSS/PAH）3, the modified WISPR biosensor is more sensitive to the low concentration（〈0.01 mg/mL） of streptavidin. And the sensing sensitivity can be further increased by one order of magnitude compared with that of the biotin/PAH coated WISPR biosensor. Thus, such low-cost, high-performance and efficient PEM-coated WISPR biosensors have great potentials in a diverse array of fields such as medical diagnostics, drug screening, food safety analysis, environmental monitoring, and homeland security.