Probe Absorption Research Articles

Terminal-conjugated non-aggregated constraints of gold nanoparticles on lateral flow strips for mobile phone readouts of enrofloxacin

Antibiotics abuse now poses a global threat to public health. Monitoring their residual levels as well as metabolites are of great importance, still challenges remain in in situ tracing during the circulation. Herein, taking the typical antibacterial Enrofloxacin (ENR) as a subject, a paper-based aptasensor was tailored by manipulating a duo of aptameric moieties to "sandwich" the target in a lateral-flow regime. To visualize the tight-binding sandwich motif more vividly, an irregular yet robust DNA-bridged gold nanoparticles (AuNPs) proximity strategy was developed with recourse to terminal deoxynucleotidyl transferase, of which the nonaggregate constraining feature was unveiled via optical absorption and scanning probe topography. This complex performed exceptionally better in the test strip context than single-particle tags, leading to an enhanced on-chip focusing. Rather than qualitative color developing, further efforts were taken to visualize the readouts in a quantitative manner by exploiting the smartphone camera for pattern recognition along with data processing in a professional App. Overall, this prototyped contraption realized a rapid and ultrasensitive quantification of ENR down to 0.1μg/L along with a broad linear range over 5 orders of magnitude, plus excellent selectivity and precision even for real samples. Such innovative fusion across DNA-structured nanomanufacturing and intelligent perception provides a prospective and invigorating solution to point-of-care inspection.

Majorana fermions induced Fano resonance and fast-to-slow light in a hybrid semiconductor/superconductor ring device

We demonstrate theoretically the Fano resonance and the conversion from fast to slow light in a hybrid quantum dot (QD)–semiconductor/superconductor (S/S) ring device, where the QD is coupled to a pair of Majorana fermions (MFs) appearing in the hybrid QD–S/S ring device. The absorption spectra of the weak probe field can exhibit a series of asymmetric Fano line shapes, and their related optical propagation properties such as fast- and slow-light effects are investigated based on the hybrid system for suitable parametric regimes. The positions of the Fano resonances can be determined by the parameters, such as different detuning regimes and QD–MFs coupling strengths. Further, the transparency windows (i.e., the absorption dip approaches zero) in the probe absorption spectra are accompanied by the rapid steep dispersion of the Fano resonance profile, which promises the slow- or fast-light effect, and even tunable fast-to-slow light propagation (or vice versa) can be achieved by controlling different parameter regimes. Therefore, Fano resonance may indicate another means to investigate MFs and the investigation may open up promising applications in quantum information processing based on MFs in solid-state devices.

Determination of atomic oxygen state densities in a double inductively coupled plasma using optical emission and absorption spectroscopy and probe measurements

A collisional radiative model for fast estimation and monitoring of atomic oxygen ground and excited state densities and fluxes in varying Ar:O2 mixtures is developed and applied in a double inductively coupled plasma source at a pressure of 5 Pa and incident power of 500 W. The model takes into account measured line intensities of 130.4 nm, 135.6 nm, 557.7 nm, and 777.5 nm, the electron densities and electron energy distribution functions determined using a Langmuir probe and multipole resonance probe as well as the state densities of the first four excited states of argon measured with the branching fraction method and compared to tunable diode laser absorption spectroscopy. The influence of cascading and self absorption is included and the validity of the used cross sections and reaction rates is discussed in detail. The determined atomic oxygen state densities are discussed for their plausibility, sources of error, and compared to other measurements. Furthermore, the results of the model are analyzed to identify the application regimes of much simpler models, which could be used more easily for process control, e.g. actinometry.

A fibered near-infrared laser heterodyne radiometer for simultaneous remote sensing of atmospheric CO2 and CH4

The performance of an all fibered near-infrared laser heterodyne radiometer (NIR-LHR) is demonstrated in ground-based solar occultation mode. A 1 × 2 fiber optical switch is employed as an alternative modulator to traditional chopper, which makes the system more stable and compact. Two distribute feedback (DFB) lasers centered at 1.6 μm and 1.65 μm, are employed as local oscillators to probe absorption lines of CO2 and CH4, respectively. After data processing and retrieval, column-averaged abundances and the mixing ratio of atmospheric CO2 and CH4 are determined based on the measurement of over six months in our laboratory (Hefei, China, 31.9°N 117.16°E). Finally, the results are validated by comparison with the GOSAT results during the same time period. The reported all fibered laser heterodyne radiometer in this manuscript has great potential to be a portable and high spectral resolution instrument for atmospheric remote sensing of multi-component gases.

A highly selective colorimetric, absorption and fluorescence probe for Al3+ detection based on a new Schiff base compound

Aluminum is the most affluent metal element in many living organisms. However, excessive Al3+ is considered to be harmful for biological activities. In the past decades, many of sensing techniques and probes were widely developed for Al3+ detection. But the low sensitivity and nonquantitative detection still need to be improved. Multi-signal probes may sweep away the obstacle. In this article, a Schiff base based on carbazole and triphenylamine as a multi-signal (colorimetric, absorption and fluorescence) probe was successfully designed, prepared and characterized. This newly designed probe, 4, 4-(9-ethyl-carbazol) methylenimine-triphenylamine(L), exhibited a “turn-on” fluorescence mode for the qualitative and quantitative detection of Al3+. The color of L changes from light yellow to orange, and the limit of detection (LOD) is 2 × 10−6 mol/L. The LODs by absorption and fluorescence methods were found to be 6.7 × 10−7 mol/L and 6.3 × 10−8 mol/L, respectively. The data of the Job’s plot, 1H NMR and LC–MS imply that L will be hydrolyzed in the presence of Al3+, and a new complex is formed based on the carbazole amide molecule and Al3+ to push the “turn-on” fluorescence. Furthermore, the fluorescence image of HeLa cells facilitating intracellular detection of Al3+ was successfully captured by the probe of L.

Transient IR (0001–0000) absorption spectroscopy of optically centrifuged N2O with extreme rotation up to J = 205

High-resolution transient IR absorption spectroscopy was used to measure (0001− 0000) R-branch transition frequencies for N2O molecules in extreme rotational states, with quantum number up to J = 205 and energies as high as Erot=17,000 cm−1. A population inversion of rotationally excited N2O states was prepared with an optical centrifuge and probed in a multi-pass IR cell using a quantum cascade laser. The optical centrifuge is based on 800-nm ultrafast, chirped laser pulses that optically trap molecules and accelerate them angularly to extreme rotational states. This work substantially increases the range of observed transitions for this band beyond the J = 100 transitions previously reported and provides benchmark measurements for theoretical predictions based on an effective Hamiltonian using a polyad model. Transient Doppler-broadened IR line profiles of N2O show that optical excitation of the sample is selectively partitioned into rotation, prior to Doppler broadening from rotation-to-translation collisional energy transfer. These results demonstrate how high-J transitions can be measured without thermal heating by coupling optical centrifuge excitation with high-resolution transient IR absorption probing.

Fano resonance induced fast to slow light in a hybrid semiconductor quantum dot and metal nanoparticle system

We theoretically demonstrate the Fano resonance and the conversion from fast to slow light in a hybrid semiconductor quantum dot (SQDs)-metal nanoparticle (MNPs) with cavity quantum electrodynamics treatment. The absorption spectra of the weak probe field exhibit a series of asymmetric Fano line shapes and their related optical propagation properties, such as fast and slow light effects, are investigated based on the hybrid system for suitable parametric regimes. Further, the transparency windows (i.e. the absorption dip approaches zero) in the probe absorption spectra are accompanied by the rapid steep dispersion of the Fano resonance profile, which promises the slow or fast light effect, and even tunable fast-to-slow light propagation (or vice versa) can be achieved by controlling different parameter regimes. Therefore the investigation may indicate promising applications in quantum information processing based on the hybrid SQD-MNP system.

Optical properties and electromagnetically induced grating in a hybrid semiconductor quantum dot-metallic nanorod system

An artificial molecule consisting of an SQD and an MNR embedded in 3D photonic crystal is proposed to realize EIG. Using the quantum mechanical density matrix approach, we have derived an expression of the absorption coefficient in the SQD in presence of MNR. Nanoparticle geometry can modify the local fields that determine SQD-MNP coupling and to engineer the hybrid optical response. The probe absorption is reduced via a strong coupling field, demonstrating spectral transparency window. It is worth noting that the background affects the relaxations of SQD. So, by making use of 3D photonic crystal as the background medium, reduced decay rate and consequently substantial local-field enhancement rate are provided. Based on EIT effect and a strong standing-wave field, diffraction grating is achievable. The first-order diffraction intensity can reach its maximum by tuning the system parameters. This model may be useful in designing new devices in all-optical communication.

Population distribution in three-level electromagnetically induced transparent system

The interaction between light and matter can be described by the theory of density matrix equations. Based on the theory, the population distribution in a ladder type three-level system under the driven of two laser fields is simulated analytically. It is found that as tuning the frequency of the probe field, the variation of population in the upper level (labeled 2) of probe absorption transition is similar to the one of probe absorption. When the phenomenon of electromagnetically induced transparency (EIT) occurs, there is no population in level 2 at the resonant frequency. This is attributed to the fact that the population in the upper level of absorption transition is related to the absorption cross section closely. The magnitude of the peak of both population and probe absorption are independent of the intensity of the coupling field. Although there is no population in level 2 as full EIT occur, but atoms distributed in the ground level (labeled 1) can be excited to the highest one (labeled 3) in the manner of two-photon resonant absorption by absorbing the probe and the coupling photons. Thus there is obvious population in level 3, and population inversion is formed between level 3 and level 2. This can be used to realize light amplification. Increasing the intensity of the probe field, the population of level 2 grows gradually until it is saturated, while the magnitude of probe absorption will undergoes a process of increase first and then decrease.

Polarization dependence of interferences inside rubidium atomic vapor governing microwave vector E-field metrology

The atom-based metrology technique has been widely accepted because of the SI traceability and dependence only on the physical constants rather than on any artefact. The presented work explains the dependence of the probe absorption on the polarization of the driving fields in the new atom-based spectroscopic technique for microwave electrometry. This work explains the nature of decays between different pathways when the fields are not only $\pi$π or $\sigma$σ polarized but also at an arbitrary angle between the two orientations. It has been shown that when any of the lasers is linearly polarized at an arbitrary angle $0\lt {\theta_{p,c}}\lt\pm\pi /2$0<θp,c<±π/2 to the quantization axis, the observation of the absorption from a correct direction becomes extremely important. The findings in this work can be utilized in the correct determination of the polarization of the incident microwave field along with the E-field amplitude measurement. Further, a challenge has been discussed when the radio frequency (RF) field is weak and cannot give the distinguished separation in the absorption peak. It has been shown that the sensitivity of the sensor can be increased in this case by detuning the RF from the on-resonance frequency.

Effects of multiple vacuum-induced coherence on absorption properties in a four-level inverted-tripod scheme atomic system

When the three transitions from the three nearly degenerate excited levels to single ground level in a four-level inverted-tripod scheme atomic system interact with the same vacuum, there appears multiple vacuum induced coherence (VIC) induced by the interference among these transitions. We investigate the effects of the VIC on the probe absorption properties, and find that the VIC from symmetric transitions enhances the central absorption, while suppresses the sideband absorptions within the double transparency spectrum. On the other hand, the VIC from nonsymmetric transitions increases the minimum value of the double transparency.

Optical detection of a subatomic particle with an ultrahigh-resolution carbon sensor

Neutron detection finds wide use in various areas, thus the improvement of the relevant instruments and methods has been focused on for a long time. For the purpose of detecting possible neutrons, in the present paper, we theoretically put forward a carbon nanotube (CNT) sensor based on a single nitrogen-vacancy center coupled to a current-carrying CNT to detect neutrons. With two lasers applied, the accreted mass landing on the nanotube may cause a frequency shift in the probe absorption spectrum. Once the frequency shift is measured, the added mass will be determined. Through the use of this sensor, owing to the small effective mass and high quality factor of the CNT, an ultrahigh mass resolution could be achieved. Due to its ultrahigh resolution, the sensor can be used to detect neutrons. Furthermore, we provide a brand new optical approach for neutron detection.

Transient amplification without population inversion in a two-field-driven ladder-type three-level system

In this paper, the transient absorption and particle population in a two-field-driven ladder-type three energy level atomic system is simulated numerically with the density matrix equations which describe the interaction of photon and material. It is found that under the radiation of strong coupling and weak probe fields, the probe absorption shows the character of damped oscillation from the time of laser being switched on to the steady state, which presents phenomenon of full transparency. There exists negative absorption during the variation process. But most of the population is on the ground state energy level all the time. This indicates that amplification without population inversion appears during the course of transparency formation. The driving of the coupling field will produce a time-dependent coherent term. Analyzing the variation of both of the population distribution and coherent term with time, it is found that transient amplification without inversion originates from the quantum interference which is related with coupling field. Thus amplification without inversion can be obtained by controlling the intensity of laser fields and the time for laser interaction.

Mapping Quasar Light Echoes in 3D with Lyα Forest Tomography

Abstract The intense radiation emitted by luminous quasars dramatically alters the ionization state of their surrounding IGM. This so-called proximity effect extends out to tens of Mpc, and manifests as large coherent regions of enhanced Lyα (Lyα) forest transmission in absorption spectra of background sightlines. Here, we present a novel method based on Lyα forest tomography, which is capable of mapping these quasar “light echoes” in three dimensions. Using a dense grid (10–100) of faint ( ) background galaxies as absorption probes, one can measure the ionization state of the IGM in the vicinity of a foreground quasar, yielding detailed information about the quasar’s radiative history and emission geometry. An end-to-end analysis—combining cosmological hydrodynamical simulations post-processed with a quasar emission model, realistic estimates of galaxy number densities, and instrument + telescope throughput—is conducted to explore the feasibility of detecting quasar light echoes. We present a new, fully Bayesian statistical method that allows one to reconstruct quasar light echoes from thousands of individual low-S/N transmission measurements. Armed with this tool, we undertake an exhaustive parameter study and show that light echoes can be convincingly detected for luminous (M 1450 &lt; −27.5 mag, corresponding to m 1450 &lt; 18.4 mag at ) quasars at redshifts 3 &lt; z QSO &lt; 5, and that a relative precision better than 20% on the quasar age can be achieved for individual objects in the expected range of ages between 1 and 100 Myr. The observational requirements are relatively modest: moderate-resolution (R ≳ 750), multiobject spectroscopy at a low signal-to-noise ratio (S/N &gt; 5) is sufficient, requiring three-hour integrations using existing instruments on 8 m class telescopes.

Micron-scale distribution of metals in Cambrian metalliferous shales, South China: Insights into local biologically driven redox disequilibrium

Early Cambrian black shales of the Niutitang Formation are found across the Yangtze Platform in a 1600-km belt extending across south China. A thin organic matter-rich layer in the lowermost part of this formation contains exceptional concentrations in Mo, Ni, Se, Re, Os, As, Hg, Sb, Ag, Au, Pt, Pd, and Ag. Due to their extreme metal enrichment, these black shales provide a rare opportunity to study the interface between semi-metals, metals and biogenic material. We report the first detailed μm-scale investigation of metal distributions and associations in samples from two sites, Zunyi and Sancha, located hundreds of km apart, using a combination of analytical techniques including X-ray fluorescence (XRF) mapping, scanning electron microscopy (SEM), Synchrotron-based XRF mapping, electron probe micro-analyser (EPMA), particle induced x-ray emission (PIXE) probe and x-ray absorption near-edge structures (XANES) imaging. Strong μm-scale variations in metal and semi-metal distributions were highlighted by Synchrotron-based XRF mapping of samples from both sites. At both locations, U is present within phosphorite nodules. Arsenic, Mo and Se are particularly abundant in the organic-rich matrix, showing strong associations with organic matter. Nickel, however, shows different distributions between the two sites. It is mainly present in association with the organic matter at the Sancha site while it is found in abundance in millerite at the Zunyi site, suggesting slightly different local conditions at Zunyi favouring Ni-S associations over Ni-organic matter. At both sites, biogenic structures were re-mineralised with laminations dominated by different metals, indicating a likely control of organic matter over metal distributions. In addition, the XANES imaging highlighted different redox states of As over μm-scale areas. While As−1 appears to be mainly present in pyrite, As+3 was mainly detected in association within the carbon and MoS2 mixed layer phase (MoSC). Overall, the present results emphasize the complexity of metal associations in this mineralised layer, the significant role of organic matter in the accumulation and precipitation of metals and semi-metals in these metalliferous shales and highlight how biogenic activity can induce μm-scale variations in redox conditions in sediments.

Wavevector mismatch and Doppler-free three-dimensional atom localization

In the regime of the Raman–Nath approximation we show coherence control of three-dimensional atom localization with high precession and resolution via probe absorption when a five-level atomic system is cyclically driven by three orthogonal standing optical wave-fields together with one traveling optical wave-field and two microwave wave-fields in an optical cavity. We apply wavevector mismatch and subsequently the Doppler-free technique to the atom localization system to minimize the imprecision in the atom’s position in the standing wave-field caused by its high velocity in the cavity. The position of the single atom is freed from the two effects by collinear coupling of the driving fields with the atom in the cavity. The atomic position is controlled in the sub-wavelength domain of the standing wave-field with probability and high quality resolution by adjusting the relative phase and amplitude of the driving fields.

A novel turn-on fluorescent probe for Hg2+ detection based on rhodamine B spirolactam derivative

ABSTRACTIn this work, a new turn-on fluorescent probe 1 for Hg2+ ions detection based on rhodamine B spirolactam was reported. Among tested metal ions, probe 1 shows high selectivity towards Hg2+ in the the mixture solution of methanol and 0.02 M HEPES buffer (V/V = 9:1, pH = 7.2). No absorption and emission band of probe 1 was observed in the range from 450 to 700 nm. While only addition of Hg2+ to probe 1 could lead to appearance of a new absorption band centered at 553 nm and a fluorescence emission band around 577 nm upon excitation at 520 nm. Moreover, it exhibits excellent linear relationship (R2 = 0.9993) between fluorescence intensity at 577 nm and the concentration of Hg2+ from 1.6 to 32 μM. The sensing mechanism was proven to be spirolactam ring open induced by Hg2+ through 1H NMR, MS, absorption and fluorescence spectra. In addition, probe 1 could detect Hg2+ in real water samples and on filter paper, which demonstrates its application in environment science.

Diagnosing Drug-Induced Liver Injury by Multispectral Optoacoustic Tomography and Fluorescence Imaging Using a Leucine-Aminopeptidase-Activated Probe.

Drug-induced liver injury (DILI) is a frequent cause of hepatic dysfunction as well as the single most frequent reason for removing approved medications from the market, and multispectral optoacoustic tomography (MSOT) is an emerging and noninvasive imaging modality for diagnosing and monitoring diseases. Herein, we report an activatable optoacoustic probe for imaging DILI through detecting the activity of leucine aminopeptidase (LAP). In this probe, an N-terminal leucyl moiety serving as the LAP recognition element is linked with a chromene-benzoindolium chromophore via 4-aminobenzylalcohol group. The elevated expression of hepatic LAP as a result of DILI cleaves the leucyl moiety and causes the red-shift of the probe's absorption band, thereby generating prominent optoacoustic signals for MSOT imaging. During this process, the probe also exhibits prominent NIR fluorescence, which can be utilized for fluorescent imaging. More importantly, by rendering stacks of cross-sectional images as maximal intensity projection (MIP) images, we could precisely locate the focus of drug-induced liver injury in mice. This probe is expected to serve a powerful tool for studying physiological and pathological processes related to LAP.

An optical narrowband switch between subluminal and superluminal light propagation in the inverted-Y configuration

The propagation of a weak probe field through a four-level inverted-Y type atomic system driven by two additional coherent fields, namely the control field and the repump field, is studied. The simulated probe absorption shows that electromagnetically induced transparency and the line shape of the transparency window under a Doppler-broadened condition are dependent on the residual Doppler averaging due to the wavelength mismatch between the control and probe fields. For 87Rb the probe propagation changes from subluminal on-resonance under a Doppler-free condition to superluminal on-resonance under a Doppler-broadened condition. For both 87Rb and 133Cs, the narrow subluminal window occurring in the group index profile in a Doppler-free environment offers an excellent delay bandwidth for probe field propagation. Under this condition, the order of the delay in probe field propagation can be as long as a few hundred µs and seems quite promising in the field of optical delay generation and light storage. The analysis shows that the residual Doppler averaging has a greater impact on the switching window under the variation of the Rabi frequency of the control field as compared to that of the repump field.

Generation of new structured beams via spatially dependent transparency

We propose a new scheme for generating new structured beams via spatially dependent transparency in a three-level atomic system. Due to the joint quantum interference induced by Laguerre–Gaussian (LG) field and constant coupling field, we can achieve different spatially dependent beams by measuring the probe absorption intensity profiles. The proposed scheme may provide potential applications in optics and novel quantum technologies.