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- 2018
- metal object detection (MOD)
- wireless power transfer (WPT)
- auxiliary detection coil
- Chest X-ray (CXR)
- Computer-aided Diagnosis (CADx)
- Early detection of tuberculosis
- Electrical Engineering and Automation
- Optoelectronic Information Science and Engineering
- Shanghai Jiao Tong University
- Bandung Institute of Technology (ITB)
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Optimized signal-to-noise ratio with shot noise limited detection in Stimulated Raman Scattering microscopy
摘要： We describe our set-up for Stimulated Raman Scattering (SRS) microscopy with shot noise limited detection for a broad window of biologically relevant laser powers. This set-up is used to demonstrate that the highest signal-to-noise ratio (SNR) in SRS with shot noise limited detection is achieved with a time-averaged laser power ratio of 1:2 of the unmodulated and modulated beam. In SRS, two different coloured laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy can be transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometre resolution. Recent technological advances have resulted in an improvement of the sensitivity of SRS applications, but few show shot noise limited detection. The dominant noise source in this SRS microscope is the shot noise of the unmodulated, detected beam. Under the assumption that photodamage is linear with the total laser power, the optimal SNR shifts away from equal beam powers, where the most signal is generated, to a 1:2 power ratio. Under these conditions the SNR is maximized and the total laser power that could induce photodamage is minimized. Compared to using a 1:1 laser power ratio, we show improved image quality and a signal-to-noise ratio improvement of 8 % in polystyrene beads and C. Elegans worms. Including a non-linear damage mechanism in the analysis, we find that the optimal power ratio converges to a 1:1 ratio with increasing order of the non-linear damage mechanism.
关键词： shot noise limited detection,signal-to-noise ratio,Nonlinear Raman microscopy
更新于2025-11-21 11:08:12
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A near-infrared BODIPY-based fluorescent probe for ratiometric and discriminative detection of Hg2+ and Cu2+ ions in living cells
摘要： A near-infrared distyryl boron dipyrromethene-based sensor bearing one bis(1,2,3-triazole)amino receptor has been synthesized. This probe selectively and quickly binds to Hg2+ and Cu2+ ions in CH3CN/H2O (5:1 v/v) and exhibits remarkably blue-shifted absorption and fluorescence bands due to the inhibition of the intramolecular charge transfer process. The fluorescence changes of this probe upon binding to Hg2+ or Cu2+ ion are totally different, undergoing a ratiometric fluorescence enhancement (for Hg2+) or a fluorescence quenching (for Cu2+) mechanism. The corresponding vivid color changes can be easily seen by the naked eye. This probe was further introduced into Hela cells for living cell imaging and found to discriminate Hg2+ and Cu2+ ions through two near-infrared fluorescence emission channels. These overall results indicate that this Click-derived near-infrared BODIPY-based probe is potentially useful for ratiometric and discriminative detection of Hg2+ and Cu2+ ions in solutions and living cells.
关键词： Discriminative detection,Ratiometric,Hg2+ and Cu2+ sensor,Near-infrared,BODIPY
更新于2025-11-21 11:08:12
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Selective Detection of Trinitrophenol by Amphiphilic Dimethylaminopyridine-Appended Zn(II)phthalocyanines at the Near-Infrared Region
摘要： Novel amphiphilic Zn(II)phthalocyanines (ZnPcs) peripherally substituted with four and eight dimethylaminopyridinium units (ZnPc1 and ZnPc2) were synthesized by cyclotetramerization of the corresponding phthalonitriles. The effect of aggregation and photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties was investigated. The chemosensing ability of ZnPcs toward explosive nitroaromatic compounds was explored in aqueous medium. This study demonstrates that ZnPc1 and ZnPc2 show fluorescence quenching behavior upon interaction with different nitro analytes and show unprecedented selectivity toward 2,4,6-trinitrophenol with a limit of detection (LOD) of 0.7?1.1 ppm with a high quenching rate constant (Ksv) of 1.6?2.02 × 105. The near-infrared (NIR) fluorescence in thin films was quenched efficiently because of the photoinduced electron-transfer process through strong intermolecular π?π and electrostatic interactions. The sensing process is highly reversible and free from the interference of other commonly encountered nitro analytes. Further, experiments were performed to demonstrate the use of ZnPcs as efficient heterogeneous photocatalysts in the reduction of nitro explosives. The smart dual performance of multicharged ZnPcs in aqueous media quantifies them as attractive candidates in developing sensor materials at the NIR region and to possibly convert the toxic explosives into useful scaffolds. These results provide an interesting perspective toward elaboration of stable fluorescent systems for the selective sensing behavior of nitro explosives and their facile heterogeneous catalytic behavior in the reduction reactions.
关键词： trinitrophenol,photocatalysis,explosive detection,near-infrared,fluorescence quenching,dimethylaminopyridinium,Zn(II)phthalocyanines
更新于2025-11-21 11:08:12
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AIE active fluorescent organic nanoaggregates for selective detection of phenolic-nitroaromatic explosives and cell imaging
摘要： Development of organic nanoparticles with high fluorescence, good biocompatibility along with strong resistance to photobleaching through simple synthetic routes is important for diverse applications such as sensing and bioimaging. Herein, we present the development of a pyrene excimer nanoaggregate which shows aggregation induced emission (AIE) effect in a solvent mixture of THF and water. The pyrene based fluorescent probe, dimethyl-5-(pyren-1-ylmethyleneamino)isophthalate (5-DP) was synthesized through a simple single step condensation reaction from inexpensive reagents. The photophysical studies of nanoaggregated system further corroborates the AIE active behavior of 5-DP probe at different water fractions (?w = 0% to 90%), where the hydrogen bonding interaction between imine and water molecules led to suppression of photoinduced electron transfer (PET) inducing significant enhancement in fluorescence. The highly photostable nanoaggregates were explored as a selective fluorescence “turn off” sensor for phenolic nitroaromatics and the chemo-selectivity was highly pronounced for 2,4,6-trinitrophenol (picric acid), that showed efficient quenching in aqueous as well as solid phase, with a detection limit of 10 nM in aqueous medium. The quenching efficiency of the nanoaggregates can be ascribed to a combination of factors including efficient fluorescence resonance energy transfer, inner filter effect and coulombic interaction between picric acid and the aggregated probe molecules. Further, random aggregation of the pyrene derivative could be controlled for the formation of fluorescent spherical nanoparticles using Pluoronics P-123 block copolymers as encapsulating agents. The resulting composite could be used as a neoteric cell imaging probe with significantly less cytotoxicity, thus showing their potential biological applications.
关键词： aggregation induced emission,electron transfer,explosive detection,cell imaging,Fluorescent organic nanoaggregates
更新于2025-11-21 11:03:13
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Molecularly imprinted based surface plasmon resonance nanosensors for microalbumin detection
摘要： Human serum albumin (HSA) is a major blood plasma protein also found in urine where its existence may be a marker of some types of liver or kidney dysfunction. Herein, we fabricated a novel surface plasmon resonance (SPR) nanosensor for selective, sensitive, and label-free microalbumin detection both in aqueous and urine sample solutions. Firstly, HSA-imprinted nanoparticles were synthesized, which consist of ethylene glycol dimethacrylate and N-methacryloyl-L-leucine as a cross-linker and functional monomer. The nanoparticles were characterized by zeta-size and scanning electron microscope analyses and were dropped onto the SPR chip surface to make HSA sensitive nanosensor. Characterization studies of HSA-imprinted SPR chip were carried out by atomic force microscopy, Fourier-transform infrared spectroscopy, contact angle, and ellipsometer. The limit of detection and limit of quantification values of HSA-imprinted SPR nanosensor were calculated as 0.7 pM and 1.9 pM for the concentration range of 0.15-500 nM. Selectivity studies of HSA-imprinted SPR nanosensor were achieved with hemoglobin and transferrin proteins which were chosen as competitor molecules. HSA-imprinted SPR nanosensor was displayed highly selective and sensitive to HSA.
关键词： surface plasmon resonance,nanosensor,nanoparticles,microalbumin detection
更新于2025-11-21 11:03:13
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A novel Ag nanoparticles/TiO2 nanowires-based photodetector and glucose concentration detection
摘要： A unique vapour transport cum glancing angle deposition (VT-GLAD) technique was employed to fabricate titanium dioxide (TiO2) nanowires (NWs). The NWs were grown and assembled to form the clusters. Both brookite (412) and rutile (002) phase for TiO2 was obtained from X-ray diffraction (XRD). The d spacing of ~ 1.37 ? was calculated from the transmission electron microscopy (TEM) of TiO2 NWs, which corresponds to (002) crystal plane. The silver (Ag) nanoparticles (NPs) on TiO2 NWs were grown using thermal evaporation cum GLAD technique. The presence of Ag NPs on the TiO2 NWs enhanced the photoconduction as compared to bare TiO2 NWs device. The maximum photosensitivity of the Ag NPs/TiO2 NWs based device was recorded ~ 1.6 times compared to the bare TiO2 NWs based device at ? 2.5 V. The Ag NPs containing device was highly UV sensitive and maximum responsivity for the device was calculated to be ~ 2.3 A/W at 370 nm. The device also possessed high responsivity rejection (RR) ratio of ~ 6.5 between UV (370 nm) and visible (450 nm) light. The Ag NPs decorated TiO2 NWs based detector also showed response to white light. The different concentration of glucose into deionised (DI) water-based solution was detected precisely under white light illumination. The normalised (light/dark) detector current/glucose concentration value was decreased from ~ 0.19 to ~ 0.05 at ? 2.5 V, with an increase in glucose concentration into the solution from 40 mg/dl to 200 mg/dl.
关键词： photodetector,Ag nanoparticles,TiO2 nanowires,VT-GLAD technique,glucose concentration detection
更新于2025-11-21 11:01:37
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Sulfur and Nitrogen Co-Doped Graphene Quantum Dots as a Fluorescent Quenching Probe for Highly Sensitive Detection toward Mercury Ions
摘要： Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) were synthesized through an efficient infrared (IR)-assisted pyrolysis of glucose, urea, and ammonia sulfate at 260°C. These served as a highly selective probe for the sensing of Hg2+ ions in an aqueous solution. The IR technique can also prepare N-doped graphene quantum dots (N-GQDs), which have been compared with SN-GQDs for their fluorescence (FL) quenching sensitivities by Hg2+ ions. The FL intensities of both GQDs show decreasing functions of concentration of Hg2+ ions within the entire concentration ranges of 10 ppb?10 ppm. The sensitivity of SN-GQD is 4.23 times higher than that of N-GQD, based on the calculation of the Stern-Volmer equation. One inter-band gap structure of SN-GQDs for the detection of mercury ions is proposed. The S doping can coordinate with phenolic groups on the edge of SN-GQDs (i.e., the formation of (CxO)2Hg2+) and induce the cutting off or alleviation of photon injection paths, thereby leading to significant FL quenching. This work proves that SN-GQD offers sufficient sensitivity for probing the quality of drinking water to ensure that it contains less than 10 ppb of Hg2+ ions, as per the World Health Organization standard.
关键词： Fluorescence quenching,Nitrogen doping,Infrared-assisted heating,Graphene quantum dots,Sulfur doping,Mercury detection
更新于2025-11-19 16:56:42
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Gold nanoparticle-based plasmonic probe for selective recognition of adenosine
摘要： Adenosine, as an endogenous molecule in organisms, plays an essential role in biological processes. Here, a plasmonic probe, creatinine-Ag+/gold nanoparticle (AuNPs), is assembled for adenosine detection based on synergistic coordination on AuNPs. The A650 nm/520 nm values of AuNPs system change linearly with adenosine concentration over a range of 1.0–5.0 μM and the detection limits reached 45 nM. The adenosine detection is realized within 4 min. Furthermore, the quantitative detection of adenosine is realized by eyedropper (a function in Microsoft’s PowerPoint) for analyzing RGB value changes of colorimetric assay. Therefore, this sensor can provide accurate and rapid assay of adenosine in patients’ serum sample without complicated instrumentations.
关键词： colorimetric assay,adenosine detection,eyedropper function,gold nanoparticle,plasmonic probe
更新于2025-11-19 16:56:42
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A red-emitting fluorescent probe with large Stokes shift for real-time tracking of cysteine over glutathione and homocysteine in living cells
摘要： Fluorescent probes with high quality for highly selective detection of cysteine (Cys) are still urgently in demand because of the indispensable roles Cys plays in the biological systems. Herein, a red-emitting fluorescent probe CP was developed for the highly selective detection of Cys over glutathione (GSH) and homocysteine (Hcy) by incorporating the recognition unit into the 2-(2-(4-hydroxystyryl)-6-methyl-4H-pyran-4-ylidene) malononitrile (P-OH) fluorophore which is characterized by red emission, noteworthy Stokes shift, and appreciable photostability. Basically, CP demonstrated appreciable sensing performance toward Cys including short response time of 4 min, high sensitivity with approximately 147-fold emission enhancement, low detection limit of 41.696 nM, and good selectivity both in the solution and living cells, indicating its promising potential of visualizing Cys in biological systems.
关键词： Large Stokes shift,Fluorescence imaging,Cysteine detection,Fluorescent probe
更新于2025-11-19 16:56:35
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Two pH-responsive fluorescence probes based on indole derivatives
摘要： Two new pH ?uorescent probes 2,8-bis((E)-2-(1,1-dimethyl-1H-benzo[e]indol-2-yl)vinyl)-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (1) and 2,8-bis((E)-2-(3,3-dimethyl-3H-indol-2-yl)vinyl)-6H,12H-5,11-methanodibenzo[b,f] [1,5]diazocine (2) were designed and synthesized via ethylene bridging of the Tr?ger's Base (TB) framework and indole derivatives. As the protonation of nitrogen atoms of indole derivatives, both probes displayed the signi?cant pH-dependent spectral properties. The probing behavior toward pH variations indicated that probes exhibited excellent pH dependent behavior in the pH ranges of 2.07–7.01 (1) and 1.96–7.01 (2), especially possessing good linear response in the pH ranges of 2.50–4.00. The emissions of 1 can be reversibly switched between brilliant yellow and dark states by protonation and deprotonation. Also, the yellow-green ?uorescence emission of 2 could be quenched upon protonation. Such behaviors enable them to work as turn-o? ?uorescent pH sensors in the solution state. Furthermore, protonation and deprotonation on indole moiety nitrogen of the probe 1 and 2 provided a sensing mechanism for pH changes. In addition, both probes performed good photostability, high selectivity and excellent reversibility.
关键词： Sensors,Fluorescent probe,pH detection,Luminescence,Indole derivatives
更新于2025-11-19 16:56:35