Intrinsic Self-calibration Research Articles

A facile double-signal ratiometric sensor of creatinine based on silver nanoparticles/thionine acetate/Mxenes with intrinsic self-calibration property

In this work, a ratiometric double signals electrochemical sensing platform was constructed for creatinine (Cre) analysis employing silver nanoparticles (AgNPs)@ MXenes/thionine acetate (THAT) composites. The synthesis of MXenes/THAT composites was utilized to modify on the surface of a screen-printed electrode (SPE) via dripping coating, followed by the electro-deposition of AgNPs. While the anodic current of the AgNPs decreased in the presence of Cre due to the competive reaction for forming metal complexes, the current of THAT remained invariant, which attained a ratiometric response. Under optimized conditions, the response current ratio (IAg/ITHAT) decreases while the concentration of Cre increased linearly between 0 ∼ 1.2 mM, with 0.01 μM as a adaptive detection limit. It provided a new sensing platforming for employing double-signals nanostructures with remarkable stability and sensitivity to design ratiometic sensors for analysis of Cre in human urine samples with real-time.

Intrinsic self-calibration electrostatic-controlled ratiometric fluorescence assay of histamine in human serum and canned tuna fish samples

Bimetallic nanoclusters protected by proteins have gained significant attention in the sensing field due to their aggregation-induced emission (AIE) property. However, their applications may be restricted by the effects of temperature, pH, ethanol, and metal ions. Therefore, the development of self-assembling technology could increase the potential applications of these materials. In this study, positively charged silicon nanoparticles (SiNPs) were mixed with negatively charged bovine serum albumin-protected silver doped gold nanoclusters (BSA@AgAuNCs) through an electrostatic interaction. The resulting system exhibited dual emissions at 610 nm ((BSA@AgAuNCs) and 460 nm (SiNPs) when excited at 370 nm. The mixing of SiNPs led to an increase in the fluorescence emission of BSA@AgAuNCs due to an aggregation-induced emission (AIE) enhancement. However, the addition of histamine, which is positively charged at pH 5.5, caused the SiNPs to be triggered and adsorbed onto the surface of BSA@AgAuNCs, resulting in their disaggregation and a decrease in their fluorescence emission. Simultaneously, the blue fluorescence emission of SiNPs at 460 nm was not affected and remained unchanged. Under optimized conditions, the fluorescence response (F460/F610) showed a linear increase with the concentration of histamine in the range of 0.01–80 µM, with a detection limit (S/N = 3) of 3.0 nM. The probe demonstrated excellent sensitivity, selectivity, and reliability in quantifying histamine in complex matrices. The recoveries % values are in the range of 97–102% and 97.7–104.4% with RSD % in the range of 2.67–3.98% and 2.78–4.00% for human blood serum and canned tuna fish samples, respectively. This work presents new opportunities for the development of sensors based on self-assembling and dual emissive properties for (bio) sensing applications.

An innovative dual-signal electrochemical ratiometric determination of creatinine based on silver nanoparticles with intrinsic self-calibration property for bimetallic Prussian blue analogues.

An ultrasensitive dual-signal ratiometric electrochemical sensor was developed for creatinine detection utilizing silver nanoparticles (Ag) with intrinsic self-calibration afforded by iron-nickel bimetallic Prussian blue (FeNiPBA) analogues. The Ag@FeNiPBA exhibits two redox signals corresponding to the Ag+/Ag and Fe3+/Fe2+ systems. Adding chloride (Cl-) solution increases the anodic current of the Ag/Ag system significantly due to the formation of silver chloride through solid-state electrochemistry. While the anodic current of the Ag/Ag system decreases in the presence of creatinine due to the competitive reaction, the Fe/Fe system's anodic current remains the same, which enables a ratiometric response. Under optimized conditions, the response ratio (IAg/IFe) decreases while the creatinine concentration increases linearly between 0.015 and 140 μM, with 0.004 μM as a good detection limit (S/N = 3). These results demonstrate superior performance over previously reported methods for electrochemical creatinine determination. The high sensitivity arises from the signal amplification of the Ag/AgCl solid-state electrochemistry, while the selectivity originates from the specific interaction between Ag+ and creatinine. The Ag@FeNiPBA hybrid can quantify creatinine in real samples with good recoveries. This work opens up new opportunities for applying dual-signal nanostructures to develop electrochemical sensors for (bio)molecule detection.

Spent Nuclear Fuel passive gamma analysis and reproducibility: Application to SKB-50 assemblies

This work studies the reproducibility of passive gamma spectroscopy measurements for spent nuclear fuels (SNFs). The fifty assemblies used for this study span over a variety of initial enrichments, burnups, and cooling times. These SNFs have been measured in two different gamma axial measurement campaigns. The net peak counts are determined for Cs-137, Eu-154 and Cs-134. Furthermore, a sensitivity analysis of the relative position of the SNF and the detector is performed. Most importantly, this work describes a methodology using an intrinsic self-calibration procedure that can be used to compare the relative activities of the radionuclides without the need for detailed knowledge about the measurement set-up and its properties. The reproducibility of the Cs-137 net peak count rate ranges between 2% and 4%. Systematic reproducibility of the ratio of Eu-154 and Cs-134 to Cs-137 is between 0,4% - 5 % using the intrinsic self-calibration method.

Dual-signal intrinsic self-calibration ratio electrochemical sensor for glutathione based on silver nanoparticle decorated Prussian Blue analog

A sensitive dual-signal intrinsic self-calibration electrochemical sensor for glutathione (GSH) was developed based on the in situ electrodeposited silver nanoparticles modified nickel and iron contained Prussian Blue analog (Ag/NiFe PBA). Two different oxidation peaks ascribed to species of Ag and Fe with wide peak-to-peak potential can be found on the Ag/NiFe PBA modified electrode. In the presence of chloride ions, owing to the solid-state electrochemistry of silver chloride (AgCl), a sharp characteristic peak appeared with largely enhanced current intensity. After adding GSH, sensitive decline in the peak current of AgCl can be found for the specific interaction of Ag-GSH accompany with the “crowding-out effect”, while the peak current of NiFe PBA remains unchanged. Using the ratio of the peak currents (IAgCl/IFe) as the signal output, Ag/NiFe PBA modified electrode showed wide linear range of 0.5 nM-5 μM for the quantitative of GSH with an extremely low detection limit of 0.12 nM, showing superior performance compared with previous electrochemical methods. The sensor can be utilized for the determination of GSH in various vegetable and serum samples. The ultrasensitive solid-state electrochemistry of AgCl promoted signal amplification strategy as well as the specific recognition and competitive reaction increasing the selectivity make the ratiometric sensor great potential in bioanalysis, food analysis and early diagnosis of cancer in clinics.

Picomolar glutathione detection based on the dual-signal self-calibration electrochemical sensor of ferrocene-functionalized copper metal-organic framework via solid-state electrochemistry of cuprous chloride

Chemical biosensing techniques are essential for food analysis and disease diagnosis. Nanomaterials with redox activity show great potential in electrochemical analysis, acting as signal labels or signal amplification unit, which can reflect the targets concentration in foods and biological samples. Here, an ultra-sensitive dual-signal intrinsic self-calibration electrochemical platform for GSH was firstly fabricated based on the novel electroactive nanomaterial of ferrocene-functionalized copper metal–organic framework (Fc-Cu-MOF). Due to the solid-state electrochemical property of cuprous chloride (CuCl), a sharp characteristic peak with an increased signal appears with the coexistence of chloride ions in solution. The stronger specific affinity between Cu+ and GSH than that of Cu+ and Cl- triggers a “crowding effect” that causes the current signal of CuCl decrease greatly. Meanwhile, the peak current of ferrocene keeps unchanged as an internal reference. Based on the ratio of the peak current variation (ΔICu/ΔIFc) as the signal output, Fc-Cu-MOF modified electrode showed wider linear range in 0.1 nM −1 μM for GSH with the detection limit as low as 0.025 nM. And the sensor was successfully applied in the determination of GSH with excellent recoveries in various real samples such as food and serum samples, providing good prospect in application of bioanalysis and food screening.

Ultrasensitive dual-signal electrochemical ratiometric aptasensor based on Co-MOFs with intrinsic self-calibration property for Mucin 1

The concentration of tumor biomarker Mucin 1 (MUC 1) is highly related with many diseases, which can be employed for the early diagnosis of cancer. In this paper, an electrochemical ratiometric aptasensor with intrinsic self-calibration property for the detection of MUC 1 is presented. In this paper, Co-MOFs themselves were employed as signal substances. This strategy was fabricated by using gold nanoparticles@black phosphorus (BP) as the substrate on the electrode, followed by modification of DNA nanotetrahedrons (DTN) via Au–S bond. The terminal of DTN contains MUC 1 aptamer. In the presence of MUC 1, the signal of DNA-labeled Co-MOFs can be detected. The current signal of Co-MOFs increased and that of thionine (as reference) was unchanged upon the addition of MUC 1. Thus, an intrinsic self-calibration aptasensor was achieved. In order to simplify the modification procedure, the electrolyte solution thionine was employed as an inner reference probe. Moreover, coupling of the hybridization chain reaction (HCR) with these MOFs signal tags presents an enzyme-free method for signal amplification, endowing the proposed ratiometric biosensor detection with high reproducibility and high sensitivity. The current ratio (IIR/ISP) remained stable over 30 individual measurements performed on ten different working electrodes. Even ten repeated scans performed on a single electrode exhibited a constant current ratio. The electrochemical ratiometric aptasensor is highly sensitivity for MUC 1 with the detection limit of 1.34 fM. Our proposed ratiometric sensor has great potential for the detection of cancer-related biomarkers.

A europium metal–organic framework for dual Fe3+ ion and pH sensing

Metal–organic frameworks (MOFs) with ratiometric sensing properties are desirable for many applications due to their intrinsic self-calibration. We report the re-assessment of the sensing properties of a MOF, originally reported as containing europium(III) and 2-hydroxyterephtalic acid, and having fluorescent ratiometric iron(III) sensing properties. Synchrotron single-crystal X-ray diffraction and proton nuclear magnetic resonance (1H NMR) spectroscopy revealed that the MOF is composed of 2-methoxyterephthalate, not 2-hydroxyterephthalate as originally reported. We found that the MOF exhibits a sensor turn-off response towards Fe3+ ion concentrations in the range 0.5–3.7 ppm (band 425 nm), and a turn-on response towards a decrease of pH from 5.4 to 3.0 (band 375 nm), both resulting from the addition of acidic Fe3+ salt solution to a MOF suspension. Thus, the ratiometric sensing properties and the originally proposed mechanism no longer apply; our work reveals a dynamic quenching mechanism for the fluorescence turn-off response due to the presence of Fe3+ ions, and a ligand protonation mechanism for the turn-on response to a decrease in pH. Our work highlights the importance of a thorough investigation of the structure of any newly synthesized MOF, and, in the case of potential sensors, their selectivity and any environmental effects on their sensing behavior.

Ultrasensitive Dual-Signal Electrochemical Ratiometric Aptasensor Based on Co-MOFs with Intrinsic Self-Calibration Property for Mucin 1

Ultrasensitive Dual-Signal Electrochemical Ratiometric Aptasensor Based on Co-MOFs with Intrinsic Self-Calibration Property for Mucin 1

Assembly of Black Phosphorus Nanosheets and MOF to Form Functional Hybrid Thin-Film for Precise Protein Capture, Dual-Signal and Intrinsic Self-Calibration Sensing of Specific Cancer-Derived Exosomes.

As the emerging and noninvasive biomarkers, exosomes play an important role in cancer screening, cancer-related immune response, and the physiological process. The sensitive, specific, and efficient detection of cancer cell-derived exosomes is of significance for early cancer diagnosis of patients. This work developed a novel dual-signal and intrinsic self-calibration aptasensor of exosomes based on a functional hybrid thin-film platform. This platform was constructed via facile assembly of black phosphorus nanosheets (BPNSs) and ferrocene (Fc)-doped metal-organic frameworks (ZIF-67) on indium tin oxide (ITO) slice, followed by combining methylene blue (MB)-labeled single- strand DNA aptamer on ITO slice. The resultant aptamer-BPNSs/Fc/ZIF-67/ITO platform had dual redox-signal responses of MB (labeled on aptamer) and Fc (doped into ZIF-67). In the presence of specific cancer cell-derived exosomes, the redox current of MB regularly reduced and that of Fc (as reference) hardly changed. An intrinsic self-calibration aptasensor was achieved and enabled sensitive detection of exosomes, showing a limit of detection down to 100 particles mL-1. The aptasensor with a capability of precise protein capture can efficiently determine specific cancer cell-derived exosomes in practical human serum and plasma samples from healthy individuals and breast cancer patients. In light of excellent performances, this aptasensor can be expanded to multiple biomarkers from cell line exosomes and is beneficial for exploring advanced techniques for high-performance detection of exosomes derived from different types of cancer cells. This work promotes the development of current techniques for early cancer screening and clinical diagnosis.

Ratiometric electrochemical assay for sensitive detecting microRNA based on dual-amplification mechanism of duplex-specific nuclease and hybridization chain reaction

We propose a ratiometric electrochemical assay for detecting microRNA (miRNA) on the basis of dual-amplification mechanism by using distinguishable electrochemical signals from thionine (Thi) and ferrocene (Fc). The thiol-modified and ferrocene-labeled hairpin capture probes (CP) are first immobilized on an Au electrode via Au-S reaction. The target miRNA hybridizes with CP and unfolding the hairpin structure of CP to form miRNA-DNA duplexes. Then, kamchatka crab duplex specific nuclease (DSN) specifically cleaves the DNA in miRNA-DNA duplexes, leading to the release of miRNA and another cleaves cycle, meanwhile, numerous Fc leaves away from the electrode surface and leads to the signal-off of Fc. The residual fragment on electrode surface acts as a HCR primer to form dsDNA polymers through in situ HCR with the presence of the primer and two probes (HDNA and HDNA’), resulting in the capture of numerous DNA/Au NPs/Thi and the signal-on of Thi. The dual-amplification mechanism significantly amplifies the decrease of Fc signal and the increase of Thi signal for ratiometric readout (IThi/IFc), thus providing a sensitive method for the selective detection of miR-141 with a detection limit down to 11aM. The dual-signal ratiometric outputs have an intrinsic self-calibration to the effects from system, which is promising to be applied in biosensing and clinical diagnosis.

Passive Non-Destructive Assay based on gamma-ray spectrometry to verify UO2 samples in the form of powder and pellet

Passive Non-Destructive Assay (PNDA) gamma-spectroscopic method is employed for nuclear material verification. The investigated materials are natural (NU) and low enriched uranium (LEU) in the form of uranium dioxide (UO2) pellets and powder, respectively. A high-resolution gamma-ray spectrometer based on HPGe detector and associated electronics is used for the measurement. The spectrometer efficiency was measured experimentally using the intrinsic self-calibration method taking into account the necessary correction factors.Sample isotopic fractions were obtained using two methods; that based on the measurement of the count rate of 185.7keV gamma line of 235U and 1001keV gamma line of 234mPa (238U) employing the intrinsic self-calibration technique to calculate the activity ratio of 235U/238U. The other method is based on uranium activity ratio measurements without efficiency corrections by choosing two gamma-rays close enough in energy, one related to 235U (84.2keV gamma line of 231Th) and the other to 238U (63.3keV gamma line of 234Th).Samples were characterized by calculating uranium isotopic mass, uranium isotopic activity ratio, total uranium content and enrichment. Special attention was given at calculating absolute error of the measured quantities, as well as the statistical behavior of the measured data in terms of the well known statistical quantities. The experimental results showed good agreement with calculated data.

Intrinsic and extrinsic active self-calibration of multi-camera systems

We present a method for active self-calibration of multi-camera systems consisting of pan-tilt zoom cameras. The main focus of this work is on extrinsic self-calibration using active camera control. Our novel probabilistic approach avoids multi-image point correspondences as far as possible. This allows an implicit treatment of ambiguities. The relative poses are optimized by actively rotating and zooming each camera pair in a way that significantly simplifies the problem of extracting correct point correspondences. In a final step we calibrate the entire system using a minimal number of relative poses. The selection of relative poses is based on their uncertainty. We exploit active camera control to estimate consistent translation scales for triplets of cameras. This allows us to estimate missing relative poses in the camera triplets. In addition to this active extrinsic self-calibration we present an extended method for the rotational intrinsic self-calibration of a camera that exploits the rotation knowledge provided by the camera's pan-tilt unit to robustly estimate the intrinsic camera parameters for different zoom steps as well as the rotation between pan-tilt unit and camera. Quantitative experiments on real data demonstrate the robustness and high accuracy of our approach. We achieve a median reprojection error of $$0.95$$ 0.95 pixel.

Retrieval of temperature profiles from CHAMP for climate monitoring: intercomparison with Envisat MIPAS and GOMOS and different atmospheric analyses

Abstract. This study describes and evaluates a Global Navigation Satellite System (GNSS) radio occultation (RO) retrieval scheme particularly aimed at delivering bias-free atmospheric parameters for climate monitoring and research. The focus of the retrieval is on the sensible use of a priori information for careful high-altitude initialisation in order to maximise the usable altitude range. The RO retrieval scheme has been meanwhile applied to more than five years of data (September 2001 to present) from the German CHAllenging Minisatellite Payload for geoscientific research (CHAMP) satellite. In this study it was validated against various correlative datasets including the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Global Ozone Monitoring for Occultation of Stars (GOMOS) sensors on Envisat, five different atmospheric analyses, and the operational CHAMP retrieval product from GeoForschungsZentrum (GFZ) Potsdam. In the global mean within 10 to 30 km altitude we find that the present validation observationally constrains the potential RO temperature bias to be <0.2 K. Latitudinally resolved analyses show biases to be observationally constrained to <0.2–0.5 K up to 35 km in most cases, and up to 30 km in any case, even if severely biased (about 10 K or more) a priori information is used in the high altitude initialisation of the retrieval. No evidence is found for the 10–35 km altitude range of residual RO bias sources other than those potentially propagated downward from initialisation, indicating that the widely quoted RO promise of "unbiasedness and long-term stability due to intrinsic self-calibration" can indeed be realised given care in the data processing to strictly limit structural uncertainty. The results thus reinforce that adequate high-altitude initialisation is crucial for accurate stratospheric RO retrievals. The common method of initialising, at some altitude in the upper stratosphere, the hydrostatic integral with an upper boundary temperature or pressure value derived from meteorological analyses is prone to introduce biases from the upper boundary down to below 25 km. Also above 30 to 35 km, GNSS RO delivers a considerable amount of observed information up to around 40 km, which is particularly interesting for numerical weather prediction (NWP) systems, where direct assimilation of non-initialised observed RO bending angles (free of a priori) is thus the method of choice. The results underline the value of RO for climate applications.

Intrinsic self-calibration of non-destructive gamma spectrometric measurements determination of U, Pu and241Am isotopic ratios

The intrinsic consistency and discrete character of high resolution gamma spectrometric measurements are used in order to make self-calibration of these measurements. Both energy and overall relative efficiency (including all geometrical self-attenuation and attenuation factors as well as the detector efficiency) can be performed using the same measured spectrum. The method is particularly useful for non-destructive gamma spectrometric measurements of isotopic ratios on different nuclear material samples. As an illustration, a complete isotopic analysis of U/Pu mixed oxide rods is given. The accuracy of the isotopic measurements depends strongly on the accuracy of the available nuclear data and comparison with destructive analysis when possible facilitates the process of obtaining more accurate nuclear data for the isotopes involved. The attainable accuracy is estimated to be better than 0.5% for239Pu and241Pu measurements.