The phase state of highly oxygenated organic aerosols influences their climate and multiphase chemical properties, yet the regulatory role of distinct alkali counter-cations on their supramolecular networks remains insufficiently constrained. We investigated the phase behavior and hygroscopicity of gluconate aerosols mixed with inorganic salts, utilizing macroscopic hygroscopic growth, in situ Raman spectroscopy, and dynamic rheology. We found that counter-cation identity closely correlates with network stiffness and phase-transition trajectories. Specifically, Na+ likely promotes more compact ion–organic interactions, yielding a relatively rigid matrix (higher storage modulus) that can kinetically impede sulfate efflorescence. In sodium gluconate/ammonium sulfate mixtures, this resulted in no efflorescence during dehydration; instead, the particles effloresced at 40.1 % RH upon subsequent hydration. In contrast, K+ appears less effective in forming compact network associations, leading to a lower-rigidity matrix, enhanced water uptake, and more accessible sulfate efflorescence during dehydration. Furthermore, competitive inter-ionic interactions in mixtures containing potassium gluconate, ammonium sulfate, and sodium sulfate can perturb the organic matrix, facilitating crystallization at a higher relative humidity of 57.1 %. These findings suggest that source-dependent cations can substantially modulate the equilibration kinetics of polyhydroxy aerosols, providing physical insights for improving aerosol phase-state parameterizations in atmospheric models.

Tumor heterogeneity is the major driver of cancer drug resistance, but its quantitative in situ characterization remains difficult to probe at the single-cell level. Here, laser tweezers Raman spectroscopy (LTRS) is employed to achieve micrometer-scale, spatially resolved, label-free biochemical imaging of eight representative cancer cell lines (Jurkat, Raji, NCI-H82, HCC827, PC-9, NCI-H1437, DLD-1, and CHO). Two-dimensional Raman spectral snapshots of optically trapped single-cell lines were acquired, from which pixel-resolved Raman spectra were extracted. Characteristic Raman peak ratios associated with lipids, proteins, nucleic acids, and membrane components were mapped to reveal intracellular biochemical distributions. Based on the spatial profiles of these ratios, the spatial full width at half-maximum (fwhm) was introduced as a quantitative spatial heterogeneity marker. Hematological cancer cells (e.g., Jurkat) exhibit multipeaked distributions with narrow spatial fwhm values (∼2.0-5.3 μm), reflecting organelle-level fragmented heterogeneity, whereas solid tumor cells (e.g., NCI-H82) display single-peaked profiles with broader values (∼18.6-35.9 μm), indicating more uniform and continuous molecular organization. Furthermore, a label-free classification model based on characteristic Raman ratios enables accurate tumor phenotype discrimination. This work establishes spatial fwhm-based, spatially resolved LTRS analysis as a robust framework for quantifying single-cell heterogeneity with potential applications in early cancer screening and therapeutic monitoring.

Abstract. Atmospheric aerosols, especially internally mixed organic-inorganic aerosols, exhibit complex phase behaviors that affect their size evolution, optical properties, and chemical reactivity, ultimately impacting climate and human health. Although parameterizations for secondary organic aerosol phase state exist, predictive models based on primary predictors for efflorescence in organic-inorganic aerosols remain underdeveloped. In this study, we evaluated several chemical parameters, including equivalent O:C ratio, organic mass fractions, glass transition temperature (Tg), and viscosity (η), and identified aerosol viscosity as the primary predictor of efflorescence relative humidity (ERH) in internally mixed organic-inorganic aerosols. We developed a linear viscosity-ERH model based on ERH and log10(η), which defines the boundary conditions for aerosol efflorescence when η< 4.76 × 10² Pa·s. Additionally, we showed that efflorescence is inhibited when η> 4.76 × 10² Pa·s. Validation using an independent dataset showed strong agreement between predicted and experimentally measured ERH (R² = 0.95). A multivariate regression model incorporating η and Tg improved prediction accuracy but was limited by Tg parameterization for complex organic-inorganic mixtures. Our findings highlight the role of aerosol viscosity in controlling efflorescence and emphasize the need to develop improved aerosol viscosity measurement techniques to better constrain aerosol phase transitions in atmospheric models.

The hygroscopicity and phase state of organic aerosols can be strongly modified by alkaline neutralization, while the role of molecular stereochemistry remains unclear. In this work, optical microscopy and confocal Raman spectroscopy were used to investigate the hygroscopic growth and phase-state evolution of glucaric acid and mucic acid aerosols at pH 12.60 during dehydration-rehydration cycles. Glucaric acid particles retained droplet-like morphology throughout the humidity cycle, whereas mucic acid particles transformed into irregular solids at RH = 36.4% and did not fully recover their original spherical shape upon rehydration. The hygroscopic growth factor showed continuous change with weak hysteresis upon a RH cycle, while mucic acid exhibited pronounced efflorescence-deliquescence hysteresis. Raman spectra provided the further evidence for particle phase. The C-H stretching modes of glucaric acid exhibit disorder arrangement of hydrocarbon chain at low RH, indicating the gel. Whereas mucic acid evolved toward a more ordered solid- like spectral profile after drying. These results demonstrate that the two stereoisomeric polyhydroxy dicarboxylic acids follow fundamentally different phase-evolution pathways under alkaline conditions, highlighting the combined effects of stereochemistry and neutralization chemistry on aerosol hygroscopicity and phase state.

Microdroplet chemistry has broad implications for atmospheric science, chemical synthesis, and the origin of life. Central to these implications is reaction kinetics, which by textbook definition is independent of reaction system size. Yet this size independence breaks down in microscopic compartments, such as microdroplets. Here we synthesize historical developments and contemporary advances to examine how size-dependent kinetics in microdroplets arises from mass transport, phase partitioning, interfacial reactivity, and surface geometry─factors regulating apparent kinetics individually or synergistically. We highlight that the scaling of apparent kinetics in microdroplets is inherently nonunique. When similar scaling relationships arise from fundamentally different mechanisms, scaling analysis should be complemented by analysis of regime boundaries. On the experimental front, we summarize the laboratory analytical techniques used to measure apparent reaction kinetics in size-resolved droplets, with emphasis on their advantages and limitations in relation to key aspects of experimental design for studying the size-dependent kinetics in microdroplets.

Sulfate aerosols are produced in urban haze through multiphase SO2 oxidation catalyzed by transition-metal ions (TMIs). Yet it remains unclear how the catalytic kinetics are regulated by photochemical radicals that also participate in TMIs' redox cycles. Here, using a kinetic model, we investigate the influence of HO2 radicals on the kinetics of copper-catalyzed S(IV) oxidation by NO2-a recently identified reaction contributing to sulfate formation in China's urban haze. We find that at higher aerosol pH, more HO2 deprotonates to O-2(-), and the combined HO2/O-2(-) radical pool acts not as an oxidant, but as a reductant that converts Cu2+ to Cu+. With fewer Cu2+ ions available to activate S(IV), sulfate formation is inhibited. This inhibitory effect is enhanced at low-ionic-strength conditions owing to reduced salting-out of aqueous HO2. As the air pollution in China has been alleviated, SO2 and secondary aerosol concentration have decreased, leading to generally higher aerosol pH, lower ionic strength, and stronger atmospheric photochemical reactivities. Consequently, more HO2/O-2(-) radicals may participate in the TMIs' cycles and alter their effectiveness in catalyzing SO2 conversion. Our findings highlight the importance of TMIs' cycle through multiple simultaneous heterogeneous reactions across various pH and ionic strength conditions.

Micro-Raman spectrometers with a confocal design exhibit advantages such as high sensitivity, high spectral resolution, and high spatial resolution-owing to their high efficiency in utilizing excitation light energy and in collecting and transmitting Raman scattering signals. Thus, they have become one of the primary analytical tools in laboratories. Inverted microscopes, by orienting their light exit ports upward, offer advantages including minimal restrictions on sample volume, rapid sample replacement, and upward beam propagation (which is suitable for detecting samples in containers like petri dishes). As a result, they hold promising applications in fields such as biomaterials and optical tweezers-based Raman spectroscopy. In this study, a laser confocal inverted micro-Raman spectrometer was developed by independently designing the optical path (comprising a laser optical system, an inverted microscope, a Raman signal optical system, and a spectrometer) and integrating these components with commercially procured lasers and charge-coupled devices (CCDs) via reserved interfaces. This developed spectrometer features a stable structure, low stray light levels, minimal installation requirements, and convenient maintenance. In accordance with the General Specification for Raman Spectrometers (GB_T 40219-2021), the sensitivity and spectral resolution of the laser confocal inverted micro-Raman spectrometer were tested. The results showed: When the spectrometer's entrance slit widths were 50 and 20 mu m, the spectral resolution at the 1 710 cm(-1) peak of a neon lamp was 2.5 and 1.5 cm(-1), respectively-meeting the Class II index for "spectral resolution" specified in the General Specification; When a laser (wavelength: 532 nm, output power: 50 mW) was used as the excitation source with an exposure time of 300 s. the signal-to-noise ratios (SNRs) of the third-order Raman characteristic peak of monocrystalline silicon reached 11:1 and 20:1 when using open-electrode CCDs and backscattering CCDs, respectively. Additionally, the fourth-order peak was observable-meeting the Class I index for "signal-to-noise ratio" in the General Specification, Furthermore, the diameter of the laser-focused spot was calculated using the Rayleigh criterion, When a Leica objective lens (50X magnification, numerical aperture [NA]=0.75, focal length=0.5 mm) was employed, the spot size after the laser was focused through the objective lens was approximately 0.433 mu m. Using the optical imaging magnification formula, the magnification of the Raman signal optical system was calculated to be 200, resulting in a spot diameter of similar to 86.6 mu m at the slit. Given the spectrometer's magnification of 1, the spot diameter reaching the CCD remained similar to 86.6 mu m. With the CCD having a pixel size of 16 x 16 mu m, the spot diameter occupied approximately 5.4 pixels. When the slit width was 50 mu m, the image of the slit (formed by the spectrometer) occupied similar to 3.1 pixels on the CCD. These calculation results were verified through actual spot size measurements, Finally, details of the instrument design were discussed, including the design philosophy and opto-mechanical design method for the laser beam expander, the application of long-pass filters and associated optical path design, the numerical aperture matching between the spectrometer and the pre-slit lens, the spectrometer's structure, the selection of collimating mirrors and focusing mirrors, and the choice of incident angle for grating diffraction.

Abstract Severe urban air pollution in China is driven by a synergistic conversion of SO2, NOx, and NH3 into fine particulate matter (PM2.5). Field studies indicated NO2 as an important oxidizer to SO2 in polluted atmospheres with low photochemical reactivity, but this rapid reaction cannot be explained by the aqueous reactive nitrogen chemistry in acidic urban aerosols. Here, using an aerosol optical tweezer and Raman spectroscopy, we show that the multiphase SO2 oxidation by NO2 is accelerated for two-order-of-magnitude by a copper catalyst. This reaction occurs on aerosol surfaces, is independent of pH between 3 and 5, and produces sulfate by a rate of up to 10 µg m-3 air hr-1 when reactive copper reaches a millimolar concentration in aerosol water – typical of severe haze events in North China Plain. Since copper and NO2 are companion emitters in air pollution, they can act synergistically in converting SO2 into sulfate in China’s haze.

Nitrate aerosol is a significant component of atmospheric aerosols, and its impact on the atmospheric environment, climate, and human health has garnered increasing attention from the scientific community. The rise in nitrogen oxide emissions has led to a rapid increase in atmospheric nitrate levels. Nitrate aerosols can influence climate through direct and indirect effects, contributing to urban haze formation and acid rain production. The hygroscopicity of atmospheric aerosols plays a crucial role in determining particle size, morphology, chemical composition, heterogeneous reactivity, and cloud condensation nuclei activity. Therefore, the research on the hygroscopicity of atmospheric aerosols is helpful to reveal the complex physical and chemical processes of atmospheric aerosols, provide the formation and evolution mechanism of atmospheric haze pollution, and realize the precise prevention and control of haze pollution. The attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) technology is highly sensitive and nondestructive, allowing aerosol samples to be analyzed in their original state. It enables continuous, dynamic, real-time, and online monitoring of aerosols. In this study, ATR-FTIR was employed to determine that the weathering point of nitrate aerosol is 56.8% RH and the deliquescence point is 83.5% RH. The heterogeneous nucleation rate (Jhet) increased by approximately two orders of magnitude, from 7.29 × 108 m−2s−1 to 4.88 × 1010 m−2s−1, as humidity decreased. Conversely, the deliquescence rate (J) increased by about three orders of magnitude, from 7.5 × 10−3 s−1 to 3.56 s−1, as humidity increased. Furthermore, the study compared the effects of different substrates on the heterogeneous nucleation rate and deliquescence rate, which aids in the development of more comprehensive atmospheric models.

Particulate nitrate photolysis regenerates reactive oxidized nitrogen species (HONO and NOx) in the atmosphere, influencing tropospheric ozone, atmospheric oxidation capacity, and particulate matter formation. However, reported nitrate photolysis rates vary by orders of magnitude, and the roles of protons and the air-water interface in accelerating nitrate photolysis in deliquesced aerosols (i.e., microdroplets) remain unclear. Using confocal Raman spectroscopy and aerosol optical tweezer, we measured nitrate photolysis rate coefficients (j) in microdroplets, ranging from 5.28 × 10-8 to 9.07 × 10-6 s-1, depending on pH (3.2-7.4) and radius (3.7 μm to 6.0 mm). j remained pH-independent under proton-sufficient conditions (pH < 6.5) but decreased with increasing pH under proton-deficient conditions (pH > 6.5), resolving discrepancies in previous studies. Moreover, we identified a tipping-point radius (r* = 706 μm), below which j scales inversely with the droplet radius and above which j plateaus at the aqueous bulk value (6.73 ± 2.12 × 10-8 s-1). These findings demonstrate that nitrate photolysis occurs predominantly at the air-water interface in microdroplets. With the atmospheric aerosol pH and radii typically below these tipping points (pH* = 6.5, r* = 706 μm), the surface-driven size-dependent photolysis likely explains the variations in atmospheric particulate nitrate photolysis rates.

In the upper troposphere and lower stratosphere (UTLS), new particles frequently form to seed cloud condensation nuclei (CCN), thereby affecting radiative forcing and global climate. Iodic acid (IA) particles have been widely detected in the UTLS; however, how they form is still largely unknown. Given the abundance of nitric acid (NA) and ammonia (NH3) in the UTLS and their nucleation potential, we explore the influence of NA and NH3 on IA nucleation by quantum chemical calculations and cluster dynamics simulations. The structural analysis indicates that NA and NH3 can cluster with IA via hydrogen bonds, halogen bonds, and electrostatic attractions between ions. The small-sized IA–NA–NH3 clusters have lower free energies than typical sulfuric acid (SA)–NA–NH3 clusters in the upper troposphere, exhibiting greater stability and higher nucleation efficiency. Moreover, the NA-enhanced effect on the established efficient IA–NH3 nucleation is more evident at lower temperatures, especially with richer NA and NH3. In the extremely low-temperature UTLS, the proposed IA–NA–NH3 ternary pathway dominates nucleation, while in the mid-troposphere with higher temperatures, the role of NA is minor due to its rapid evaporation. These findings underscore the important role of NA in iodine particle formation in the UTLS, offering mechanistic insights into the missing secondary particle sources.

The directional assembly of porous organic molecules into long-range ordered architectures, featuring controlled hierarchical porosity and oriented pore channels with defined spatial arrangements, is a fundamental challenge in chemistry and materials science. Herein, using porous organic cages as starting units, we present a cooperative multiscale-assembly strategy enabling the simultaneous alignment of pore channels and directional hierarchical growth in a single step. At the microscopic level, we employed double solvents to manipulate the intermolecular packing of microporous tetrahedral [4+6] imine cages (CC1 and CC3), resulting in pore channel orientation. Concurrently, at the mesoscopic level, convective flow in the double-solvent system directed the spatial distribution of nuclei species, followed by diffusion limited growth, leading to the directional formation of single-crystal microtubes. By precisely controlling the direction of convective flow, the nanocages were successfully organized into 2D and 3D single-crystal microtube arrays while maintaining oriented micropores. This hierarchical porous architecture enhanced mass transfer, as confirmed by adsorption measurements. Interestingly, such 3D hierarchical microtube arrays can be utilized to immobilize Pd clusters and enzymes (lipase or Glucose oxidase) within the micro- and macropores, respectively, showing a 3.8- to 4-fold enhancement in one-pot tandem reaction activity compared to physical mixtures of individual analogues.

The oxidation of gas-phase SO2 to sulfate aerosols has been a driver of urban air pollution since the Great Smog of London in 1952. Traditionally, this reaction has been perceived as a quintessential atmospheric aqueous reaction, occurring within condensed water such as cloud and fog droplets. This established view has been challenged by recent studies showing that, in urban air pollution, sulfate aerosols form predominantly through a heterogeneous SO2 conversion at aerosol surfaces. This review summarizes recent advances in understanding this heterogeneous process, focusing on (a) why S(IV) oxidation is faster at the air-water interface, (b) how to experimentally determine the reaction location with the scaling relationships of apparent reaction kinetics, and (c) how to predict, or retrieve, the localized surface reaction kinetics with multiscale models. We conclude by discussing open questions and remaining challenges, with the central theme of how the interfacial heterogeneous process may redefine our understanding of atmospheric sulfur chemistry.

In this study, the effect of accumulative back extrusion (ABE) on the microstructure and tensile properties of AZ91D alloy was investigated under different conditions. The results reveal that the deformation temperature and solid solution time exerted significant influences on the microstructure. In a 24h sample (solution treatment), the average grain size of the 280 degrees C/3 passes sample was refined to 2.93 mu m, which was associated with the deformation accumulation during the alternating loading process and the dispersion of the /I-Mg17Al12 phase. The coarse /I phase gradually transforms into continuous precipitation (CP) and discontinuous precipitation (DP) ways through solution treatment. Microstructure analysis reveals that the /I phases were mainly distributed along the grain boundaries, contributing to inhibiting the migration of grain boundaries. The plasticity of the AZ91D alloy was remarkably improved under the ABE process. In the 310 degrees C/3 passes sample, the ultimate tensile strength (UTS) of the AZ91D alloy reached 239.37 MPa, and the elongation was 24.35 %. Compared with the initial as-cast sample, its strength and elongation increased by 177.9 % and 324.7 %, respectively, attributed to the transformation of deformed AZ91D alloys from the typical brittle fracture to the ductile fracture mode. The significantly elevated grain boundaries in fine-grained magnesium alloys served to coordinate deformation. This work provides a new processing technology for the design of high-strength and high-ductility bulk materials of AZ91D alloy, as well as scientific guidance for the development of fine-grained magnesium alloy.

The construction of complex artificial hierarchical compartmentalized hosts that enable interhost electron communication to modulate─or even amplify─material properties remain a significant challenge. Herein, we report a supramolecular host-in-host assembly formed by electrostatic interactions between deprotonated hydroxyl-functionalized organic cages and bipyridinium bearing poly(ionic liquid)s (PILs). In this architecture, anionic cages are encapsulated within a polymeric network, creating a hierarchical structure that integrates discrete molecular hosts within an extended network. Benefiting from well-organized arrangement and cooperative functionality of dual-host components, UV light-triggered interhost electron transfer─from electron-rich O- sites in the cages to electron-deficient pyridinium N+ centers in the PILs─is realized. This electronic interplay markedly enhances the material's physicochemical properties, yielding a ∼500-fold increase in conductivity and a high near-infrared (NIR) photothermal conversion (808 nm) efficiency of ∼82.2%. Incorporation of Pd clusters into the cage cavities further highlights the role of interhost electron communication in modulating the local catalytic environment─reshaping the electronic structure of Pd and the charge distribution around hydroxyl-lined cage windows to promote substrate orientation, adsorption and transport. Coupled with the nanofurnace effect of the nested architecture, these features collectively lead to markedly enhanced catalytic activity and selectivity in hydrogenation reactions.

The excess of iodine (I2) and potassium ferrocyanide (K-4[Fe(CN)(6)]) to table salt are harmful to both human health and environment. To date, there are still a lack of suitable methods for simple, rapid and in-situ to detect the I-2 and K-4[Fe(CN)(6)] contents in table salt. Herein, we employ a highly sensitive Raman spectroscopy, which is based on multiple reflection cavities and multi-directional signal collection optical systems, to detect the concentration of trace ions in table salt. The detection limit of our technology is less than 1 mg/kg in salt solutions, signifying that the corresponding quantitative detection limit in table salt is 3.45 mg/kg. Simultaneously, the relative Raman intensity of the ion exhibits a highly linear correlation with concentration (R-2 = 0.999), rendering it a molecular probe for I-2 and K-4[Fe(CN)6] within table salt. The accuracy of this molecular probe for I-2, K-4[Fe(CN)(6)], and sulfate (SO42-) content in different salts is 87.2 %, 89.6 % and 95.6 % respectively.Compared with the traditional method, this method has the advantages of low sample consumption (1g of salt), fast detection speed (10 min), and the measured sample can be saved.

Biomarkers are widely used and accepted for the prediction, diagnosis, and post-treatment monitoring of critical diseases, in both clinic and research. However, the rapid determination of biomarker levels in fluid samples remains a significant challenge. Point-of-care testing is an emerging platform that enables instant and accurate biomarker analysis by integrating advanced biosensors with portable signal analysis systems. In this study, we developed a biosensing platform by combining a flexible sensing array, an immuno-microfluidic biochip, and a signal acquisition/processing unit for rapid protein biomarker detection aimed at cancer screening. The platform consists of an immuno-microfluidic biochip for biomarker capture and pressure sensor activation, a flexible sensing array for signal detection, and a signal acquisition/processing unit to analyze and display the results. The microfluidic biosensing platform achieved a limit of detection of 40 pg/ml and a linear operating range from 0.1 to 150 ng/ml (R-2 = 0.98) in blood serum samples, with excellent stability and selectivity. The platform can process up to 10 samples simultaneously within 48 minutes. Clinical testing of cancer samples showed a correlation of similar to 98.7 % between the biosensing platform and commercial equipment, confirming its high accuracy. This biosensing platform offers an advanced approach for biomarker analysis in cancer screening and diagnosis, with potential applications in the detection and monitoring of other diseases.