Search

Designing reactive surface clusters at the nanoscale on metal‐oxide supports enables selective molecular interactions in low‐temperature catalysis and chemical sensing. Yet, finding effective material combinations and identifying the reactive site remains challenging and an obstacle for rational catalyst/sensor design. Here, the low‐temperature oxidation of formaldehyde with CuOx clusters on Co3O4 nanoparticles is demonstrated yielding an excellent sensor for this critical air pollutant. When fabricated by flame‐aerosol technology, such CuOx clusters are finely dispersed, while some Cu ions are incorporated into the Co3O4 lattice enhancing thermal stability. Importantly, infrared spectroscopy of adsorbed CO, near edge X‐ray absorption fine structure spectroscopy and temperature‐programmed reduction in H2 identified Cu+ and Cu2+ species in these clusters as active sites. Remarkably, the Cu+ surface concentration correlated with the apparent activation energy of formaldehyde oxidation (Spearman's coefficient ρ = 0.89) and sensor response (0.96), rendering it a performance descriptor. At optimal composition, such sensors detected even the lowest formaldehyde levels of 3 parts‐per‐billion (ppb) at 75°C, superior to state‐of‐the‐art sensors. Also, selectivity to other aldehydes, ketones, alcohols, and inorganic compounds, robustness to humidity and stable performance over 4 weeks are achieved, rendering such sensors promising as gas detectors in health monitoring, air and food quality control. [ABSTRACT FROM AUTHOR]

Chemiluminescence (CL) is of great significance in biochemical analysis and imaging due to its high sensitivity and lack of need for external excitation. In this review, we summarized the recent progress of AIE-based CL systems, including their working mechanisms and applications in biochemical analysis, bioimaging, and disease diagnosis and treatment. In ion and molecular detection, CL shows high selectivity and high sensitivity, especially in the detection of dynamic reactive oxygen species (ROS). Further, the integrated NIR-CL single-molecule system and nanostructural CL platform harnessing CL resonance energy transfer (CRET) have remarkable advantages in long-term imaging with superior capability in penetrating deep tissue depth and high signal-to-noise ratio, and are promising in the applications of in vivo imaging and image-guided disease therapy. Finally, we summarized the shortcomings of the existing AIE-CL system and provided our perspective on the possible ways to develop more powerful CL systems in the future. It can be highly expected that these promoted CL systems will play bigger roles in biochemical analysis and disease theranostics. [ABSTRACT FROM AUTHOR]

Abstract Designing reactive surface clusters at the nanoscale on metal‐oxide supports enables selective molecular interactions in low‐temperature catalysis and chemical sensing. Yet, finding effective material combinations and identifying the reactive site remains challenging and an obstacle for rational catalyst/sensor design. Here, the low‐temperature oxidation of formaldehyde with CuOx clusters on Co3O4 nanoparticles is demonstrated yielding an excellent sensor for this critical air pollutant. When fabricated by flame‐aerosol technology, such CuOx clusters are finely dispersed, while some Cu ions are incorporated into the Co3O4 lattice enhancing thermal stability. Importantly, infrared spectroscopy of adsorbed CO, near edge X‐ray absorption fine structure spectroscopy and temperature‐programmed reduction in H2 identified Cu+ and Cu2+ species in these clusters as active sites. Remarkably, the Cu+ surface concentration correlated with the apparent activation energy of formaldehyde oxidation (Spearman's coefficient ρ = 0.89) and sensor response (0.96), rendering it a performance descriptor. At optimal composition, such sensors detected even the lowest formaldehyde levels of 3 parts‐per‐billion (ppb) at 75°C, superior to state‐of‐the‐art sensors. Also, selectivity to other aldehydes, ketones, alcohols, and inorganic compounds, robustness to humidity and stable performance over 4 weeks are achieved, rendering such sensors promising as gas detectors in health monitoring, air and food quality control.

Aptamers are short, single-stranded DNA or RNA molecules that selectively bind to a target molecule. Aptamer-complement duplex (ACD) is often used to design molecular switches capable of producing a detectable signal or triggering a structural change upon aptamer binding to a target. However, such aptamer switch generally faces an increased dissociation constant (Kd) due to the energy barrier of the complementary duplex. We reported a competitive hybridization mechanism to modulate the binding affinity of an ACD to a target adenosine. Using the computation-guided design, we calculated the aptamer folding energy for the duplex length from 11-nt to 15-nt, and experimentally measured increased apparent Kd values resulted from these extended duplexes. Using a set of strands to compete with the ACD hybridization, it reduced the aptamer folding energy to facilitate aptamer switches with decreased apparent Kd values ranging from over 400 μM without a competing strand to ∼30 μM with a competing strand. This competitive aptamer switch was also found sensitive to single-nucleotide mutations of a competing strand. Our work provides an approach to modulate the binding affinity and the sensitivity of aptamer-complement duplexes, which could be useful in the nucleic acids-based sensing and nanomedicine.

DNA ligases are essential enzymes involved in DNA replication and repair processes in all organisms. These enzymes seal DNA breaks by catalyzing the formation of phosphodiester bonds between juxtaposed 5′ phosphate and 3′ hydroxyl termini in double-stranded DNA. In addition to their critical roles in maintaining genomic integrity, DNA ligases have been recently identified as diagnostic biomarkers for several types of cancers and recognized as potential drug targets for the treatment of various diseases. Although DNA ligases are significant in basic research and medical applications, developing strategies for efficiently detecting and precisely quantifying these crucial enzymes is still challenging. Here, we report our design and fabrication of a highly sensitive and specific biosensor in which a stable DNA hairpin is utilized to stimulate the generation of fluorescence signals. This probe is verified to be stable under a wide range of experimental conditions and exhibits promising performance in detecting DNA ligases. We anticipate that this hairpin-based biosensor will significantly benefit the development of new targeting strategies and diagnostic tools for certain diseases. [ABSTRACT FROM AUTHOR]

Chemiluminescence (CL) is of great significance in biochemical analysis and imaging due to its high sensitivity and lack of need for external excitation. In this review, we summarized the recent progress of AIE-based CL systems, including their working mechanisms and applications in biochemical analysis, bioimaging, and disease diagnosis and treatment. In ion and molecular detection, CL shows high selectivity and high sensitivity, especially in the detection of dynamic reactive oxygen species (ROS). Further, the integrated NIR-CL single-molecule system and nanostructural CL platform harnessing CL resonance energy transfer (CRET) have remarkable advantages in long-term imaging with superior capability in penetrating deep tissue depth and high signal-to-noise ratio, and are promising in the applications of in vivo imaging and image-guided disease therapy. Finally, we summarized the shortcomings of the existing AIE-CL system and provided our perspective on the possible ways to develop more powerful CL systems in the future. It can be highly expected that these promoted CL systems will play bigger roles in biochemical analysis and disease theranostics.

Surface-enhanced Raman scattering (SERS) is a well-established surface-sensitive technique for detecting trace amounts of molecular analytes. While the impact of surface singularities on plasmonic materials has been widely studied, the fabrication of cost-effective, efficient SERS substrates remains a challenge. In this paper, we present the study of large-area nanorough Au SERS-active substrates, elaborated by thermal evaporation deposition by photoemission electron microscopy (PEEM), a high-resolution near-field mapping technique, to access the statistical properties of the hot-spot distribution. We experimentally demonstrate that the near-field PEEM and far-field Raman statistical signatures of nanorough Au surfaces are quantitatively correlated when used for molecular sensing. The maximum of the SERS signal of thiophenol (TP) molecules diluted to 10–6 M is observed near the film percolation threshold for which the hot-spot density is maximum. Finally, SERS measurements from solutions of TP, crystal violet, and rhodamine B molecules at 10–8 M demonstrated the sensitivity of our substrates for molecular sensing. [ABSTRACT FROM AUTHOR]

1,3,5-tris-(4 formyl phenyl) benzene and p-Phenylenediamine based covalent organic framework (COF) i.e., National University of Singapore-15 (NUS-15) have been synthesized using the solvothermal method at room temperature. Importantly, synthesized NUS-15 has been analysed using powdered X-ray diffraction (PXRD), Field emission scanning electron microscopy (FE-SEM), Infrared and UV-Visible spectroscopy techniques. Afterward, the optical properties of NUS-15 (excitation wavelength = 298 nm, emission wavelength = 404 nm) were confirmed through a photoluminescence spectrophotometer. Later on, biofunctionalization of NUS-15 was performed with Anti-BSA using coordination chemistry and confirmed through various analysis techniques. Based on optical properties, NUS-15-based Bioconjugate i.e., Anti-BSA@ NUS-15, has been utilized for selective sensing applications and noted 0.366 ppm detection limit for BSA. Our results imply that NUS-15 might be applied in future biomedical applications. Synopsis. In this work, a covalent organic framework i.e., NUS-15 was synthesised and characterised for Anti-BSA tagged through simple coordination chemistry. Later, Anti BSA-tagged NUS-15 was explored for selective BSA sensing in a certain range using a photoluminescence spectrophotometer. Our results confirm 1.11 ppm (limit of quantification) and 0.366 ppm (limited of detection) during BSA detection. [ABSTRACT FROM AUTHOR]

Noncovalent interactions between single-stranded DNA (ssDNA) oligonucleotides and single wall carbon nanotubes (SWNTs) have provided a unique class of tunable chemistries for a variety of applications. However, mechanistic insight into both the photophysical and intermolecular phenomena underlying their utility is lacking, which results in obligate heuristic approaches for producing ssDNA-SWNT based technologies. In this work, we present an ultrasensitive "turn-on" nanosensor for neuromodulators dopamine and norepinephrine with strong relative change in fluorescence intensity (Δ F/ F0) of up to 3500%, a signal appropriate for in vivo neuroimaging, and uncover the photophysical principles and intermolecular interactions that govern the molecular recognition and fluorescence modulation of this nanosensor synthesized from the spontaneous self-assembly of (GT)6 ssDNA rings on SWNTs. The fluorescence modulation of the ssDNA-SWNT conjugate is shown to exhibit remarkable sensitivity to the ssDNA sequence chemistry, length, and surface density, providing a set of parameters with which to tune nanosensor dynamic range, analyte selectivity and strength of fluorescence turn-on. We employ classical and quantum mechanical molecular dynamics simulations to rationalize our experimental findings. Calculations show that (GT)6 ssDNA form ordered rings around (9,4) SWNTs, inducing periodic surface potentials that modulate exciton recombination lifetimes. Further evidence is presented to elucidate how dopamine analyte binding modulates SWNT fluorescence. We discuss the implications of our findings for SWNT-based molecular imaging applications.

Information on the temporal and spatial scale of cellular molecules in biological systems is crucial for estimating life processes and may be conducive to an improved understanding of disease progression. This intracellular and extracellular information is often difficult to obtain at the same time due to the limitations of accessibility and sensing throughput. DNA is an excellent material for in vivo and in vitro applications, and can be used to build functional modules that can transform bio-information (input) into ATCG sequence information (output). Due to their small volume and highly amenable programming, DNA-based functional modules provide an opportunity to monitor a range of information, from transient molecular events to dynamic biological processes. Over the past two decades, with the advent of customized strategies, a series of functional modules based on DNA networks have been designed to gather different information about molecules, including the identity, concentration, order, duration, location, and potential interactions; the action of these modules are based on the principle of kinetics or thermodynamics. This paper summarizes the available DNA-based functional modules that can be used for biomolecular signal sensing and transformation, reviews the available designs and applications of these modules, and assesses current challenges and prospects.

DNA ligases are essential enzymes involved in DNA replication and repair processes in all organisms. These enzymes seal DNA breaks by catalyzing the formation of phosphodiester bonds between juxtaposed 5′ phosphate and 3′ hydroxyl termini in double-stranded DNA. In addition to their critical roles in maintaining genomic integrity, DNA ligases have been recently identified as diagnostic biomarkers for several types of cancers and recognized as potential drug targets for the treatment of various diseases. Although DNA ligases are significant in basic research and medical applications, developing strategies for efficiently detecting and precisely quantifying these crucial enzymes is still challenging. Here, we report our design and fabrication of a highly sensitive and specific biosensor in which a stable DNA hairpin is utilized to stimulate the generation of fluorescence signals. This probe is verified to be stable under a wide range of experimental conditions and exhibits promising performance in detecting DNA ligases. We anticipate that this hairpin-based biosensor will significantly benefit the development of new targeting strategies and diagnostic tools for certain diseases.

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health. [ABSTRACT FROM AUTHOR]

Magnetic particle spectroscopy (MPS) in the Brownian relaxation regime, also termed magnetic spectroscopy of Brownian motion (MSB), can detect and quantitate very low, sub-nanomolar concentrations of molecular biomarkers. MPS/MSB uses the harmonics of the magnetization induced by a small, low-frequency oscillating magnetic field to provide quantitative information about the magnetic nanoparticles' (mNPs') microenvironment. A key application uses antibody-coated mNPs to produce biomarker-mediated aggregation that can be detected using MPS/MSB. However, relaxation changes can also be caused by viscosity changes. To address this challenge, we propose a metric that can distinguish between aggregation and viscosity. Viscosity changes scale the MPS/MSB harmonic ratios with a constant multiplier across all applied field frequencies. The change in viscosity is exactly equal to the multiplier with generality, avoiding the need to understand the signal explicitly. This simple scaling relationship is violated when particles aggregate. Instead, a separate multiplier must be used for each frequency. The standard deviation of the multipliers over frequency defines a metric isolating viscosity (zero standard deviation) from aggregation (non-zero standard deviation). It increases monotonically with biomarker concentration. We modeled aggregation and simulated the MPS/MSB signal changes resulting from aggregation and viscosity changes. MPS/MSB signal changes were also measured experimentally using 100 nm iron-oxide mNPs in solutions with different viscosities (modulated by glycerol concentration) and with different levels of aggregation (modulated by concanavalin A linker concentrations). Experimental and simulation results confirmed that viscosity changes produced small changes in the standard deviation and aggregation produced larger values of standard deviation. This work overcomes a key barrier to using MPS/MSB to detect biomarkers in vivo with variable tissue viscosity. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman scattering (SERS) is a sensitive, fast, and nondestructive technology to detect trace amounts of molecules. The development of ultrasensitive and environmentally stable noble‐metal‐free SERS substrates is crucial for practical applications but still very challenging. In this contribution, an in situ substitutional doping strategy to synthesize Re‐doped WSe2 (Re‐WSe2) with different doping levels is reported. By increasing the Re content to ≈50 at%, the Re‐WSe2 alloy inherits the 1T″ phase of the ReSe2 lattice. Furthermore, Nb atoms are doped into the 1T″ Re‐WSe2 alloy to further modulate its electronic structure. The as synthesized 1T″ Nb, Re‐WSe2 demonstrates a femtomolar‐level molecular sensing capability with a detectable concentration of 5 × 10–15m and the corresponding enhancement factor is 2.0 × 109, which is superior to that of most non‐noble‐metal SERS substrates and comparable or even superior to that of noble‐metal substrates to the best of the authors' knowledge. More importantly, the as‐synthesized 1T″ Nb, Re‐WSe2 exhibits excellent air‐stability over a long term (≈6 months) and selective detection capability in the mixed molecular solution, which are essential for their practical applications. The work provides a new strategy for the rational design of noble‐metal‐free SERS substrates to achieve ultrasensitive molecular sensing. [ABSTRACT FROM AUTHOR]

Graphene-based terahertz (THz) devices have emerged as promising platforms for a variety of applications, leveraging graphene's unique optoelectronic properties. This review explores recent advancements in utilizing graphene in THz technology, focusing on two main aspects: THz molecular sensing and THz wave modulation. In molecular sensing, the environment-sensitive THz transmission and emission properties of graphene are utilized for enabling molecular adsorption detection and biomolecular sensing. This capability holds significant potential, from the detection of pesticides to DNA at high sensitivity and selectivity. In THz wave modulation, crucial for next-generation wireless communication systems, graphene demonstrates remarkable potential in absorption modulation when gated. Novel device structures, spectroscopic systems, and metasurface architectures have enabled enhanced absorption and wave modulation. Furthermore, techniques such as spatial phase modulation and polarization manipulation have been explored. From sensing to communication, graphene-based THz devices present a wide array of opportunities for future research and development. Finally, advancements in sensing techniques not only enhance biomolecular analysis but also contribute to optimizing graphene's properties for communication by enabling efficient modulation of electromagnetic waves. Conversely, developments in communication strategies inform and enhance sensing capabilities, establishing a mutually beneficial relationship., (© 2024 Wiley‐VCH GmbH.)

Due to its highly conjugated panel-like structure and unique photophysical and chemical features, anthracene has been widely used for fabricating attractive and functional supramolecular assemblies, including two-dimensional metallacycles and three-dimensional metallacages. The embedded anthracenes in these assemblies often show synergistic effects on enhancing the desired supramolecular and luminescent properties. This review focuses on the metallasupramolecular architectures with anthracene-containing building blocks, as well as their applications in host-guest chemistry, stimulus response, molecular sensing, light harvesting, and biomedical science. [ABSTRACT FROM AUTHOR]

Nanomaterials as artificial enzymes (nanozymes) have aroused extensive research interest owing to their highly stable, long storage period, and low-cost alternatives to enzymes. Recent significant advances in nanozymes open up new opportunities for the development of nanozymes in a wide range of applications due to their ultra-small size, good stability, and high biocompatibility. Many efforts have been devoted to the exploration of enzyme mimetic activities and their diverse applications by modulating the catalytic activities of nanozyme. In this review, practical introduction to the identification effect of the bio-templates (e.g. , biopolymers and hybrid biomolecules) on the biocatalytic performances of nanozymes is summarized. Then, the focus is on exciting advances of three efficient modulators in the nanozymes to improve the performance of catalytic activities in molecular sensing systems, including photo-modulation, plasmonic excitations, and charge-transfer interactions. Furthermore, we briefly describe the state-of-the-art advances in nanozyme-based molecular sensing of certain nanozymes as probes for the detection of cancer biomarkers, antioxidants, neurotransmitters, antibiotics, and toxin molecules. Eventually, it is anticipated to shed light on the further development of nanozymes for molecular detection by highlighting the current challenges and prospects for modulating the catalytic activities of diverse nanomaterials. [Display omitted] • The effect of the bio-templates on the biocatalytic performances of nanozymes has been reviewed. • The effects of photo-modulation, plasmonic excitations, and charge-transfer interactions activity have been discussed. • Nanozyme-based biosensors for the detection of various biologically important molecules were highlighted. [ABSTRACT FROM AUTHOR]

This review presents a comprehensive synopsis of the recent developments and achievements in the research of nanosensors composed of plasmonic nanoparticles (NPs) and silicon nanostructures (NSs) for effective trace-level molecular detection. This review focuses intensively on the methodologies for the preparation and enforcement of a variety of SiNSs including (a) metal nanoparticles decorated silicon nanowires (NWs), (b) metal nanodendrites (NDs) on Si substrate, (c) plasmonic NPs decorated nanocrystalline porous silicon (pSi), and (d) silicon composed hybrid nanostructures with favorable parameters of importance in sensing. Furthermore, their potency in wide molecular sensing applications, especially chemical, biological, and explosive molecules based on surface enhanced Raman scattering (SERS) phenomenon is discussed in detail. Various demonstrations and categorizations are provided on the topic of Si-based NSs for a clear understanding to diverse readers. A roadmap is also provided at the end for achieving superior sensing materials or devices in the future. [ABSTRACT FROM AUTHOR]

The recent pandemic has shown that accurate and on-demand information on various infections requires highly versatile, Point-of-Care (PoC) platforms providing diagnostic and prognostic multiparametric information, personalized to each patient. Despite the significant progress made over the last years in various biosensing technologies, existing solutions fail to meet the power and area requirements needed for highly scalable and portable next-generation PoC devices. This work presents a solution based on a first of its kind fully integrated electronic-photonic platform in a zero-change high volume CMOS-SOI process, tailored towards molecular and ultrasound sensing applications. Leveraging co-integration of $10\mu \text{m}$ micro-ring resonators (MRRs) with on-chip electronics, we address the current needs of scalability, power and area by providing nanophotonic sensing and readout processing on a monolithic electronic-photonic system-on-chip (EPSoC). This work unlocks the door towards complete and self-contained Lab-on-Chip (LoC) systems, capable of providing multiparametric biosensing information.

Mid-infrared (mid-IR) optical spectroscopy of molecules is of large interest in physics, chemistry, and biology. However, probing nanometric volumes of molecules is challenging because of the strong mismatch of their mid-infrared absorption and scattering cross-sections with the free-space wavelength. We suggest overcoming this difficulty by nanofocusing acoustic graphene plasmon polaritons (AGPs) – oscillations of Dirac charge carriers coupled to electromagnetic fields with extremely small wavelengths – using a taper formed by a graphene sheet above a metallic surface. We demonstrate that due to the appreciable field enhancement and mode volume reduction, the nanofocused AGPs can efficiently sense molecular fingerprints in nanometric volumes. We illustrate a possible realistic sensing sсenario based on AGP interferometry performed with a near-field microscope. Our results can open new avenues for designing tiny sensors based on graphene and other 2D polaritonic materials.

The power of sensing molecules is often characterized in part by determining their thermodynamic/dynamic properties, in particular the binding constant of a guest to a host. In many studies, traditional nonlinear regression analysis has been used to determine the binding constants, which cannot be applied to complex systems and limits the reliability of such calculations. Supramolecular sensor systems include many interactions that make such chemical systems complicated. The challenges in creating sensing molecules can be significantly decreased through the availability of detailed mathematical models of such systems. Here, we propose uncovering accurate thermodynamic parameters of chemical reactions using better-defined mathematical modeling-fitting analysis is the key to understanding molecular assemblies and developing new bio/sensing agents. The supramolecular example we chose for this investigation is a self-assembled sensor consists of a synthesized receptor, DPA (DPA = dipicolylamine)-appended phenylboronic acid (1) in combination with Zn2+(1.Zn) that forms various assemblies with a fluorophore like alizarin red S (ARS). The self-assemblies can detect multi-phosphates like pyrophosphate (PPi) in aqueous solutions. We developed a mathematical model for the simultaneous quantitative analysis of twenty-seven intertwined interactions and reactions between the sensor (1.Zn-ARS) and the target (PPi) for the first time, relying on the Newton-Raphson algorithm. Through analyzing simulated potentiometric titration data, we describe the concurrent determination of thermodynamic parameters of the different guest-host bindings. Various values of temperatures, initial concentrations, and starting pHs were considered to predict the required measurement conditions for thermodynamic studies. Accordingly, we determined the species concentrations of different host-guest bindings in a generalized way. This way, the binding capabilities of a set of species can be quantitatively examined to systematically measure the power of the sensing system. This study shows analyzing supramolecular self-assemblies with solid mathematical models has a high potential for a better understanding of molecular interactions within complex chemical networks and developing new sensors with better sensing effects for bio-purposes.

Magnetic particle spectroscopy (MPS) in the Brownian relaxation regime, also termed magnetic spectroscopy of Brownian motion (MSB), can detect and quantitate very low, sub-nanomolar concentrations of molecular biomarkers. MPS/MSB uses the harmonics of the magnetization induced by a small, low-frequency oscillating magnetic field to provide quantitative information about the magnetic nanoparticles’ (mNPs’) microenvironment. A key application uses antibody-coated mNPs to produce biomarker-mediated aggregation that can be detected using MPS/MSB. However, relaxation changes can also be caused by viscosity changes. To address this challenge, we propose a metric that can distinguish between aggregation and viscosity. Viscosity changes scale the MPS/MSB harmonic ratios with a constant multiplier across all applied field frequencies. The change in viscosity is exactly equal to the multiplier with generality, avoiding the need to understand the signal explicitly. This simple scaling relationship is violated when particles aggregate. Instead, a separate multiplier must be used for each frequency. The standard deviation of the multipliers over frequency defines a metric isolating viscosity (zero standard deviation) from aggregation (non-zero standard deviation). It increases monotonically with biomarker concentration. We modeled aggregation and simulated the MPS/MSB signal changes resulting from aggregation and viscosity changes. MPS/MSB signal changes were also measured experimentally using 100 nm iron-oxide mNPs in solutions with different viscosities (modulated by glycerol concentration) and with different levels of aggregation (modulated by concanavalin A linker concentrations). Experimental and simulation results confirmed that viscosity changes produced small changes in the standard deviation and aggregation produced larger values of standard deviation. This work overcomes a key barrier to using MPS/MSB to detect biomarkers in vivo with variable tissue viscosity.

Due to its highly conjugated panel-like structure and unique photophysical and chemical features, anthracene has been widely used for fabricating attractive and functional supramolecular assemblies, including two-dimensional metallacycles and three-dimensional metallacages. The embedded anthracenes in these assemblies often show synergistic effects on enhancing the desired supramolecular and luminescent properties. This review focuses on the metallasupramolecular architectures with anthracene-containing building blocks, as well as their applications in host-guest chemistry, stimulus response, molecular sensing, light harvesting, and biomedical science.

Taste sensors using photonics, termed artificial photonic tongues, have emerged as a promising platform for intuitive taste discrimination. However, the need for complex binding protocols for each taste profile limits their applicability to a narrow range of taste molecules. Here, we introduce an intriguing "binding-free" approach to molecular taste sensing using plasmonics, eliminating the requirement for physical or chemical binding protocols. We develop a wafer-scale plasmonic metasurface constructed by coating metallic nanoparticles in a scalable manner onto a metallic mirror. This metasurface functions to detect molecular refractive indices and surface tensions via 2D projection optical images of an array of liquid droplets containing the taste molecules on top, which can immediately visualize and distinguish between the five basic tastes of molecules (including their mixtures) as well as other additional spicy and alcoholic tastes. We anticipate that this intuitive and rapid taste-sensing approach has the potential to establish a user-friendly and portable taste-sensing platform.

Designing reactive surface clusters at the nanoscale on metal-oxide supports enables selective molecular interactions in low-temperature catalysis and chemical sensing. Yet, finding effective material combinations and identifying the reactive site remains challenging and an obstacle for rational catalyst/sensor design. Here, the low-temperature oxidation of formaldehyde with CuO x clusters on Co 3 O 4 nanoparticles is demonstrated yielding an excellent sensor for this critical air pollutant. When fabricated by flame-aerosol technology, such CuO x clusters are finely dispersed, while some Cu ions are incorporated into the Co 3 O 4 lattice enhancing thermal stability. Importantly, infrared spectroscopy of adsorbed CO, near edge X-ray absorption fine structure spectroscopy and temperature-programmed reduction in H 2 identified Cu + and Cu 2+ species in these clusters as active sites. Remarkably, the Cu + surface concentration correlated with the apparent activation energy of formaldehyde oxidation (Spearman's coefficient ρ = 0.89) and sensor response (0.96), rendering it a performance descriptor. At optimal composition, such sensors detected even the lowest formaldehyde levels of 3 parts-per-billion (ppb) at 75°C, superior to state-of-the-art sensors. Also, selectivity to other aldehydes, ketones, alcohols, and inorganic compounds, robustness to humidity and stable performance over 4 weeks are achieved, rendering such sensors promising as gas detectors in health monitoring, air and food quality control., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Two-dimensional metallic NbS2 has attracted increasing attentions due to its excellent properties. So far, the preparations of NbS2 are mainly focused on the mechanical exfoliation and molecular beam epitaxial (MBE), both of which have limitations, such as, small lateral sizes (usually

With diameters close to the wavelength of the guided light, optical microfibers (MFs) can guide light with tight optical confinement, strong evanescent fields and manageable waveguide dispersion and have been widely investigated in the past decades for a variety of applications. Compared to silica MFs, which are ideal for working in visible and near-infrared regions, chalcogenide glass (ChG) MFs are promising for mid-infrared (mid-IR) optics, owing to their easy fabrication, broad-band transparency and high nonlinearity, and have been attracting increasing attention in applications ranging from near-field coupling and molecular sensing to nonlinear optics. Here, we review this emerging field, mainly based on its progress in the last decade. Starting from the high-temperature taper drawing technique for MF fabrication, we introduce basic mid-IR waveguiding properties of typical ChG MFs made of As2S3 and As2Se3. Then, we focus on ChG-MF-based passive optical devices, including optical couplers, resonators and gratings and active and nonlinear applications of ChG MFs for mid-IR Raman lasers, frequency combs and supercontinuum (SC) generation. MF-based spectroscopy and chemical/biological sensors are also introduced. Finally, we conclude the review with a brief summary and an outlook on future challenges and opportunities of ChG MFs.

Microlasers are emerging tools for biomedical applications. In particular, whispering‐gallery‐mode (WGM) microlasers are promising candidates for sensing at the biointerface owing to their high quality‐factor and potential in molecular assays, and intracellular and extracellular detection. However, lasing particles with sensing functionality remain challenging since the overlap between the WGM optical mode and external gain medium is much lower compared to internal gain inside the cavity. To overcome this problem, the concept of Förster resonant energy transfer (FRET) is exploited on WGM droplet microlaser by separating donor and acceptor molecules at the cavity–surface interface. It is first discovered that the interfacial FRET laser not only originates from conventional FRET but utilizes coherent radiative energy transfer (CRET) to excite acceptor molecules by inducing light‐harvesting effect near the cavity interface. Simulations and experiments have revealed that the absorption spectrum of individual analyte plays a crucial role in interfacial FRET laser. Distinct lasing spectra can therefore distinguish molecules of different absorption properties upon binding. Finally, detection of small fluorescent molecules and photosynthetic protein is performed. The results presented here not only demonstrate the wide‐ranging potential of microlaser external cavity implementation in molecular sensing applications, but also provide comprehensive insights into cavity energy transfer in laser physics. [ABSTRACT FROM AUTHOR]

The method of realizing nanostructures using porous alumina templates has attracted interest due to the precise geometry and cheap cost of nanofabrication. In this work, nanoporous alumina membranes were utilized to realize a forest of nanowires, providing a bottom-up nanofabrication method suitable for surface-enhanced Raman spectroscopy (SERS). Gold and iron were electroplated through the straight channels of the membrane. The resulting nanowires are, indeed, made of an active element for plasmonic resonance and SERS as the hexagonal distribution of the nanowires and the extreme high density of the nanowires allows to excite the plasmon and detect the Raman signal. The method to reduce the distance between pores and, consequently, the distance of the nanowires after electrodeposition is optimized here. Indeed, it has been predicted that the light intensity enhancement factor is up to 1012 when the gap is small than 10 nm. Measurements of Raman signal of thiol groups drying on the gold nanowires show that the performance of the device is improved. As the thiol group can be linked to proteins, the device has the potential of a biosensor for the detection of a few biomolecules. To assess the performance of the device and demonstrate its ability to analyze biological solutions, we used it as SERS substrates to examine solutions of IgG in low abundance ranges. The results of the test indicate that the sensor can convincingly detect biomolecules in physiologically relevant ranges.

Owing to their superior fluorescence performance, inexpensive synthesis and nontoxic nature, carbon dots (C-dots) are systematically explored in a variety of applications; in this review, we outline and critically discuss recent trends with respect to their potential exploitation in criminal investigation, forensic toxicology and anti-counterfeit interventions. Capitalising on their colour-tuneable behaviour (in the sense that they adopt different colours with respect to the incident radiation), C-dot-based compositions are ideal for the visual enhancement of latent fingerprints, affording improved contrast against multicoloured and patterned backgrounds. As highly sensitive and highly selective optical nanoprobes, C-dots show excellent analytical performance in detecting biological compounds, drugs, explosives, heavy metals and poisonous reactants. In addition, benefiting from their versatile structural and chemical composition, C-dots can be incorporated into ink and polymeric formulations capable of functioning as a new generation of cost-effective barcodes and security nanotags for object authentication and anti-counterfeit applications. Translating these encouraging research outcomes into real-life innovations with significant social and economic impact requires an open, multidisciplinary approach and a close synergy between materials scientists, biologists, forensic investigators and digital engineers.

A new colorimetric and fluorescent chemosensor for visual determination of carbonate ions was developed by the microwave assisted solvent free synthesis of 7,8-dihydroxy-3-(4-methylphenyl) coumarin ( DHMC ). The structural characterization of DHMC was confirmed by microanalysis and spectroscopy methods (MALDI-TOF, FT-IR, 1 H NMR, 13 C NMR, and 2D HETCOR). The binding behaviors of DHMC were investigated towards various anions by UV–vis and fluorescence spectroscopy. DHMC showed a selective and sensitive fluorometric and colorimetric responses towards carbonate ion over other anions. The detection limit of CO 3 2- was found to be 1.03 µM. Moreover, the fluorescence imaging in living cells suggests that DHMC has a great potential in the biological imaging application. It has been demonstrated that DHMC can be used as a rapid and reliable sensor for the determination of carbonate anion in a variety of practical applications. [ABSTRACT FROM AUTHOR]

Abstract: We investigate fabrication of a higher‐order nanostructure consisting of Au nanoparticles using convective self‐assembly in a lab‐chemical chip to serve a wide range of applications in life science, medical diagnosis, environmental analysis, and food safety. Our higher‐order nanostructure devices enable highly sensitive detection of various molecules by an easy operation of in situ surface enhanced Raman scattering platform using a simple Raman spectrometer. [ABSTRACT FROM AUTHOR]

Plasmonic perfect absorbers (PPAs) have promising properties to be utilized in molecular sensing and spectroscopy applications such as surface enhanced infrared absorption (SEIRA) and surface enhanced Raman spectroscopy (SERS). In order to employ these properties and demonstrate the great potential of PPAs, investigation and demonstration of PPA designs and their sensing applications are highly needed. In this context, we present the design, optical characterization, experimental realization and dual-band sensing application of a subwavelength PPA array for infrared detection and surface enhanced spectroscopy applications. We analyze the PPA to investigate the absorption spectra and the fine-tuning mechanism through the parameter sweep simulations and experiments. In order to understand the absorption mechanism, we investigate the charge and current density distribution maps with electric and magnetic field enhancement effects. Additionally, we demonstrate the potential usage and reliability of the proposed PPA by presenting the experimental results of the dual-band detection of a conformal polymethyl methacrylate layer with nanometer-scale thickness atop the PPA. According to the experimental and simulation results of this study, the proposed PPA can be utilized in multiband molecular detection and high sensitive spectroscopy applications. [ABSTRACT FROM AUTHOR]

The spectral shift between near- and far-field responses of the plasmonic nanoantennas has negative effects on the performance of surface-enhanced spectroscopy measurements. In order to reduce these effects, we propose use of the plasmonic absorber (PA) concept that promises lower spectral-shift between the near- and far-field responses. In this context, we present the design, characterization and experimental realization of a novel PA structure which utilizes hexagonally arranged nanoantennas operating in the mid-infrared regime. Additionally, we analyze the PA device numerically and experimentally to investigate tunability of resonant modes. To reveal the absorption mechanism, we investigate the near-field distribution maps in addition to the charge and current density distributions. With the aim of comparing the proposed PA device with the conventional particle-based nanoantenna according to the amount of spectral shift between the near- and far-field peaks, we present the near- and far-field spectra of each configuration and show that PA structure exhibits significantly lower spectral-shift. Finally, we present the effect of reduced spectral-shift on the surface-enhanced infrared absorption spectroscopy through the simulations for the detection of the molecular absorption mode of a polymer and compare with the results of particle nanoantenna configuration. [ABSTRACT FROM AUTHOR]

Magnetic particles are widely used as signal labels in a variety of biological sensing applications, such as molecular detection and related strategies that rely on ligand-receptor binding. In this review, we explore the fundamental concepts involved in designing magnetic particles for biosensing applications and the techniques used to detect them. First, we briefly describe the magnetic properties that are important for bio-sensing applications and highlight the associated key parameters (such as the starting materials, size, functionalization methods, and bio-conjugation strategies). Subsequently, we focus on magnetic sensing applications that utilize several types of magnetic detection techniques: spintronic sensors, nuclear magnetic resonance (NMR) sensors, superconducting quantum interference devices (SQUIDs), sensors based on the atomic magnetometer (AM), and others. From the studies reported, we note that the size of the MPs is one of the most important factors in choosing a sensing technique. [ABSTRACT FROM AUTHOR]

Four new metal-organic frameworks of [Co 4 (biimb) 3 (DSBPDC) 2 (H 2 O) 3 ]·9H 2 O ( 1 ), [Cd 2 (biimb) 2 (DSBPDC)(H 2 O)]·DMF·5.5H 2 O ( 2 ), [Cd 2 (biimb)(DSBPDC)(H 2 O) 3 ]·H 2 O ( 3 ) and [Cd 3 Co(biimb) 2 (DSBPDC) 2 (H 2 O) 6 ]·2H 2 O ( 4 ) (DMF = N , N -dimethylformamide) have been successfully synthesized by reactions of corresponding metal salts with imidazol-containing ligand 1,3-bis(1-imidazolyl)-5-(imidazol-1-ylmethyl)benzene (biimb) and 3,3′-disulfobiphenyl-4,4′-dicarboxylic acid (H 4 DSBPDC) under solvothermal conditions. The complexes were characterized by single crystal and powder X-ray diffractions, IR and thermogravimetric analyses. 1 is a 3D framework accompanied by antiferromagnetic interactions within the dinuclear Co(II) centers. 2 is a microporous 3D framework with different pore sizes and shapes along b and c axes, while 3 and 4 have the same 3D framework structure. Selectively gas adsorption and molecular sensing properties of the frameworks were investigated. [ABSTRACT FROM AUTHOR]

In this paper, new non-conjugated luminescent glycol-terephthalate oligomers were obtained by means of free radical reaction between glycol-terephthalate oligomers and the corresponding aryl Schiff bases. This route demonstrated to be a better strategy than ionizing or plasma treatments in terms of processing facility, short reaction time, reproducibility and added value of resulting fluorescent materials. All compounds were characterized by NMR, IR/ATR, TGA-DTA, GPC, MALDI-TOF-MS, and XPS techniques. The thermal behavior for the functionalized oligomers was also studied. The optical properties of functionalized oligomers and the aryl Schiff bases have been determined and display fluorescent quantum yields below 6.24%. In a preliminary carbon dioxide sensing test, the anthracenyl oligomer showed a good linearity (R2 = 0.928) with a limit of detection and quantification of 415 and 1258 μM, respectively. To the best of our knowledge, this is the first report on the preparation of luminescent glycol-terephthalate oligomers for the fluorescent sensing of carbon dioxide. [Display omitted] • Functionalized oligomers were prepared by free radical reaction. • The functionalization strategy allows to obtain a high functionalization ratio. • The optical properties of functionalized oligomers have been determined. • Anthracenyl oligomer shows the ability to suppress aggregation-induced quenching. • The anthracenyl oligomer showed sensing characteristics with a good linearity. [ABSTRACT FROM AUTHOR]