Ways for improving the sensing of nano-bio-sensors

The nano-bio-sensoristic sector is one of the mainstreams of nanotechnology and requires careful information for constant improvement of the nanodevice performance. The sensing/sensitivity plays a peculiar role, is a determinant characteristics, able to cause a great improvement of the device quality.The paper provides a detailed analysis on the casuistry for increasing the performanceof nano-systems through enhanced diffusion, studied with the use of a recent analytical transport model, able to accommodate previously not completely understood behaviours and to predict new interesting features at nanoscale.

Differential Microstrip Sensor for Complex Permittivity Characterization of Organic Fluid Mixtures

A microstrip highly sensitive differential sensor for complex permittivity characterization of urine samples was designed, fabricated and tested. The sensing area contains two pairs of open-stub resonators, and the working frequency of the unloaded sensor is 1.25 GHz. The sensor is easily implemented on an affordable substrate FR-4 Epoxy with a thickness of 1.6 mm. A Teflon beaker is mounted on the sensor without affecting the measurements. Numerically, liquid mixtures of water and urine at different percentages were introduced to the proposed sensor to evaluate the frequency variation. The percentage of water content in the mixture varied from 0% (100% urine) to 100% (0% urine) with a step of 3.226%, thus giving 32 data groups of the simulated results. Experimentally, the mixtures of: 0% urine (100% water), 20% urine (80% water), 33% urine (66% water), 50% urine (50% water), 66% urine (33% water), and 100% urine (0% water) were considered for validation. The complex permittivity of the considered samples was evaluated using a nonlinear least square curve fitting in MATLAB in order to realize a sensing sensitivity of about 3%.

Florescence Intensity Ratio Thermometer in the First Biological Window Based on Non-Thermally Coupled Energy Levels of Tm3+ and Ho3+ Ions

In this study, the up-conversion luminescence and optical temperature sensing properties of Ho3+/Tm3+/Yb3+-co-doped NaLuF4 phosphors were investigated. The visible (475, 540, and 650 nm) and near-infrared light (692 and 800 nm) radiated from 1Ho3+/4Tm3+/Yb3+-co-doped NaLuF4 phosphors were obvious enough for subsequent detection. The slopes in the lnI–lnP plot of the emissions located in the first biological window (650, 692, and 800 nm) were both ∼1.5, which mean that the power had little effect on the three fluorescence peak ratios. Based on the florescence intensity ratios (FIRs) of 650 and 692 nm, the relative sensing sensitivity reaches 0.029 K−1 (476 K). The relative sensing sensitivity based on the FIRs of 800 and 692 nm reaches 0.0076 K−1 (476 K). The results reveal that 1Ho3+/4Tm3+/Yb3+-co-doped NaLuF4 phosphors have potential applications in FIR-based temperature sensing in biological tissue for their high sensing sensitivity. In addition, the emission colors of the sample stabilize in the white light region as the temperature increased from 303 to 467 K, implying that it can also be used in white display.

Up-Converting Luminescence and Temperature Sensing of Er3+/Tm3+/Yb3+ Co-Doped NaYF4 Phosphors Operating in Visible and the First Biological Window Range

Accurate and reliable non-contact temperature sensors are imperative for industrial production and scientific research. Here, Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors were studied as an optical thermometry material. The typical hydrothermal method was used to synthesize hexagonal Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors and the morphology was approximately rod-like. The up-conversion emissions of the samples were located at 475, 520, 550, 650, 692 and 800 nm. Thermo-responsive emissions from the samples were monitored to evaluate the relative sensing sensitivity. The thermal coupled energy level- and non-thermal coupled energy level-based luminescence intensity ratio thermometry of the sample demonstrated that these two methods can be used to test temperature. Two green emissions (520 and 550 nm), radiated from 2H11/2/4S3/2 levels, were monitored, and the maximum relative sensing sensitivities reached to 0.013 K−1 at 297 K. The emissions located in the first biological window (650, 692 and 800 nm) were monitored and the maximum relative sensing sensitivities reached to 0.027 (R692/650) and 0.028 K−1 (R692/800) at 297 K, respectively. These results indicate that Er3+/Tm3+/Yb3+ co-doped NaYF4 phosphors have potential applications for temperature determination in the visible and the first biological window ranges.

Experimental Research on the Sensitivity of Partial Discharge Ultra High Frequency Sensor Structure Parameters

With the development of intelligent high voltage switch, online gas insulated switchgear discharge detection technology has been more and more widely applied. Because of the high sensing sensitivity and good antiinterference performance of build-in partial discharge sensor, it is currently required to install them on gas insulated switchgear products with voltage levels of 220 kV and above at the factory. The structural parameters of the build-in partial discharge sensor is of great importance to its sensing sensitivity. Therefore, in this paper, the influence of the structure change on the sensitivity of axisymmetric gas insulated switchgear build-in partial discharge sensor is experimentally studied. A practical gas insulated switchgear test model was established in the laboratory, and the frequency domain measurement system based on Spectrogram analyzer and synchronous sweep signal generator was adopted. By comparing the insertion loss generated by the build-in sensor when receiving sweep signal, the influence of structural parameter changes on the sensing sensitivity was analyzed. The results show that the diameter of the build-in sensor should be matched with the diameter of the hand-hole. The match of the larger diameter of the hand-hole and the smaller diameter of the sensor can increase the sensing sensitivity, but when the diameter of the sensor is close to the diameter of the hand-hole, the sensitivity will be significantly reduced. In addition, metal bolts with the sensor electrode and its insulating support fixed to the hand-hole cover can also result in a significant reduction in sensing sensitivity. Using the same measuring principle and system, the propagation attenuation characteristics of partial discharge ultra high frequency signal in gas insulated switchgear typical structures (linear and L-shaped structures) are also experimentally studied. The results show that the average attenuation of partial discharge ultra high frequency signal in gas insulated switchgear along the linear distance is 0.3 dB/m, and the attenuation through every L-shaped structure is 4.2 dB.