Stability Of Ions Research Articles

Unravelling Lithium Interactions in Non-Flammable Gel Polymer Electrolytes: A Density Functional Theory and Molecular Dynamics Study

Lithium metal batteries (LiMBs) have emerged as extremely viable options for next-generation energy storage owing to their elevated energy density and improved theoretical specific capacity relative to traditional lithium batteries. However, safety concerns, such as the flammability of organic liquid electrolytes, have limited their extensive application. In the present study, we utilize molecular dynamics and Density Functional Theory based simulations to investigate the Li interactions in gel polymer electrolytes (GPEs), composed of a 3D cross-linked polymer matrix combined with two different non-flammable electrolytes: 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC)/dimethyl carbonate (DMC) and 1 M lithium bis(fluorosulfonyl)imide (LiFSI) in trimethyl phosphate (TMP) solvents. The findings derived from radial distribution functions, coordination numbers, and interaction energy calculations indicate that Li⁺ exhibits an affinity with solvent molecules and counter-anions over the functional groups on the polymer matrix, highlighting the preeminent influence of electrolyte components in Li⁺ solvation and transport. Furthermore, the second electrolyte demonstrated enhanced binding energies, implying greater ionic stability and conductivity relative to the first system. These findings offer insights into the Li+ transport mechanism at the molecular scale in the GPE by suggesting that lithium-ion transport does not occur by hopping between polymer functional groups but by diffusion into the solvent/counter anion system. The information provided in the work allows for the improvement of the design of electrolytes in LiMBs to augment both safety and efficiency.

Encapsulation of Antarctic krill peptide by polysaccharide-based nanoparticles: Preparation, characterization, evaluation of stability and hypoglycemic activity

The aim of this study was to construct a chitosan quaternary ammonium salt (HTCC)/sodium alginate (SA) nanoparticle delivery system for the encapsulation of Antarctic krill peptide (AKP), with the goal of enhancing its stability and post-digestive hypoglycemic activity. Additionally, the effect of the content and encapsulation sequence of HTCC/SA on the structure and properties of AKP-loaded nanoparticles (AKP-loaded NPs) was investigated. As the content of the outermost wall material (HTCC) increased, the particle size of nanoparticles initially increased and then decreased. Concurrently, the zeta potential showed a trend of increase, ranging from -38.77 to 46.07 mV. When SA was used as the outermost wall material, the nanoparticles exhibited a smaller particle size (240.1 nm) and better dispersibility. Electrostatic interaction and hydrogen bonding were the major forces involved in the formation of AKP-loaded NPs. X-ray diffraction revealed that AKP was successfully encapsulated in an amorphous state. Scanning electron microscopy showed that AKP-loaded NPs had an elliptical or blocky appearance. Moreover, AKP-loaded NPs demonstrated good storage and temperature stability, while nanoparticles with HTCC in the outermost layer (HTCC:SA=2:1) showed good pH and ionic stability. During simulated digestion, AKP-loaded NPs inhibited the release of AKP in gastric fluid. Consequently, the hypoglycemic activity of digested AKP-loaded NPs was remarkably higher than unencapsulated AKP. Notably, the nanoparticles with HTCC in the outermost layer provided superior hypoglycemic activity. In summary, the polysaccharide-based delivery system exhibited great potential to improve the stability and post-digestive hypoglycemic activity of AKP, broadening its applications in the food and pharmaceutical industries.

Novel food-grade water-in-water emulsion fabricated by amylopectin and tara gum: Property evaluation and stability analysis

To surmount the limitation of the instability of the currently reported water-in-water (W/W) emulsions, novel W/W emulsionss were constructed using amylopectin (AMP) and tara gum (TG) as the phases, and differently shaped ovalbumin (OVA) particles were used as stabilizers to improve the stability of W/W emulsions. Experiments displayed that the conformation of OVA could be changed by heating treatment, thus forming fibrous or spherical OVA particles that had the potential to stabilize TG-in-AMP (TG/AMP) emulsions. The emulsions had the best stability when the pH was 4 and the concentration of OVA particles was 3 %. Moreover, since ovalbumin fibril (OVAF) had better adsorption at the water-water interface than ovalbumin sphere (OVAS), OVAF-stabilized TG/AMP emulsion (OF-TE) had a relatively denser interfacial layer and exhibited more satisfactory ionic stability and physical stability than OVAS-stabilized TG/AMP emulsion (OS-TE). The rheological results demonstrated that OVAF and OVAS had little effect on the viscosity of TG/AMP emulsions. In brief, OVAF was more effective in improving the stability of TG/AMP emulsions than OVAS, and OF-TE did not show phase separation for at least 5 days. This study may be of great significance in improving the stability of food-grade W/W emulsions.

Perovskite Solar Cells: Challenges Facing Polymeric Hole Selective Materials in p–i–n Configuration

AbstractPolymeric hole‐selective materials (P‐HSMs) offer advantages like solution processability, tunable energy levels, and improved mechanical stability, making them suitable for large‐scale and flexible substrates. Poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) based p–i–n perovskite solar cells exhibit promising power conversion efficiency (PCE), but wettability, dopant, and cost challenges necessitate the development of advanced next‐generation P‐HSMs. To provide a clear understanding of the structural property with photovoltaic performance, this review classifies such newly developed P‐HSMs into five distinct structural categories. Specifically, this review discusses the current status, advancements, challenges, and prospects in structural design and synthetic variations, focusing on enhancing photovoltaic performance, wettability, mitigating surface defects, and stability. Notably, incorporating polar units into P‐HSMs enhances wettability and mitigates ion instabilities and uncoordinated lead defects. Promising structural designs like polymeric self‐assembled monolayers and in situ polymerized hole‐selective materials are examined. Despite performance advancements, emerging, P‐HSMs face significant challenges such as limited thermal stress analysis (55–85 °C) and scalability restricted to small‐scale devices. To bridge this gap, this review emphasizes the urgent need for prioritizing thermal stability testing and large‐scale device fabrication in future research, paving the way for commercial viability of P‐HSMs in p–i–n perovskite photovoltaics.

Effect of combined treatments of hydrolysis and succinylation on the solubility and emulsion stability of rennet casein and micellar casein

Casein is the most abundant protein in milk with good emulsifying properties and bioavailability. However, the tight micellar structure of casein results in poor solubility. In the case of soft solid materials such as processed cheese, imitation cheese, yoghurt and protein-based oil-in-water emulsions, poor solubility directly affects the homogeneity and stability of the texture structure of such products, leading to a poor user experience. In this study, two protein modification techniques, hydrolysis and succinylation, were combined to improve the solubility of casein and the stability of its emulsions. The individual and combined effects of enzymatic hydrolysis and succinylation modification approaches on the stability of rennet casein (RC) and micellar casein (MC) emulsions were further explored. After double-treatment of casein with enzymatic hydrolysis and succinylation, the solubility of RC and MC was up to about 95 %, which was superior to that of single-treatment. Fourier transform infrared spectroscopy showed that the characteristic wave signals of the double-treated samples were located between the two single-treated samples, and that there may be an opposite effect between the two modifications. After 21 days of storage, the emulsions prepared from double-treated caseins still remained stable. The salt ionic stability and freeze-thaw stability were significantly improved, and the physical stability of MC was increased by nearly three times. The results explained the effects of enzymatic hydrolysis and succinylation on the functional properties of casein, provided a reference for the development of food systems based on oil-in-water emulsions, and offered a new idea for the wide application of succinylated casein.

Soy glycinin-carboxymethyl cellulose “chain bead-like” nanocomplexes: Focus on formation mechanism, functional characteristics and stability properties

In this study, the aim was to solve the problem of poor functional characteristics and stability of soy glycinin (11S). 11S and carboxymethyl cellulose (CMC) nanocomplexes (SCs) were prepared by pH-driven method. They were further analyzed for the effects on the SCs formation mechanism, function and stability properties of CMC concentration (0.05%, 0.1%, 0.5%, 1%, w/v) and degree of substitution (DS, 0.7, 0.9, 1.2). The particle size and zeta potential indicated that the SCs were small in size, uniformly distributed, and high in potential. Classical DLVO theory calculation, FTIR, 3D fluorescence spectroscopy, and UV spectroscopy revealed that 11S and CMC interact mainly through electrostatic forces and hydrogen bonding, and the secondary and tertiary structures of the protein were altered. SEM, AFM and TEM showed that 11S formed “protein nanobeads” and engulfed the “chain” of CMC, generating “chain bead-like” SCs. With the increase in CMC concentration and DS, the hydrophobicity decreased and the molecular flexibility increased of SCs. The solubility, turbidity, emulsifying and foaming properties showed the tendency to enhance and then decrease as the CMC concentration increased; these properties improved better when the DS was stronger. The optimum functional characteristics of the formed SCs were obtained when the concentration and DS of CMC were 0.5% and 1.2, respectively. Furthermore, the addition of CMC significantly improved the pH, ionic stability and thermal stability of the nanocomplexes. This study will provide a theoretical basis for deeper understanding of the mechanism of pH-driven protein-polysaccharide interactions and applications in functional foods.

Millimeter-wave high-wavenumber scattering diagnostic developments on EAST and NSTX-U.

A pioneering 4-channel, high-k poloidal, millimeter-wave collective scattering system has been successfully developed for the Experimental Advanced Superconducting Tokamak (EAST). Engineered to explore high-k electron density fluctuations, this innovative system deploys a 270GHz mm-wave probe beam launched from Port K and directed toward Port P (both ports lie on the midplane and are 110° part), where large aperture optics capture radiation across four simultaneous scattering angles. Tailored to measure density fluctuations with a poloidal wavenumber of up to 20cm-1, this high-k scattering system underwent rigorous laboratory testing in 2023, and the installation is currently being carried out on EAST. Its primary purpose lies in scrutinizing ion and electron-scale instabilities, such as the electron temperature gradient (ETG) mode, by furnishing measurements of the kθ (poloidal wavenumber) spectrum. This advancement significantly bolsters the capacity to probe high-k electron density fluctuations within the framework of EAST. Beam tracing and data interpretation modules developed for both EAST and NSTX-U high-k scattering diagnostics are described.

Detection of a low-frequency ion instability in a magnetic nozzle

Abstract A low-frequency ion instability, with frequency f I between the ion gyrofrequency and the lower hybrid frequency f c , i < f I ≪ f LH , is detected in an argon plasma expanding in a magnetic nozzle for magnetic fields between 240 < B z , max < 700 G. The frequency of the instability exhibits a linear dependence with magnetic field strength, and the wave amplitude has a radial maximum that would match the location of a conical density structure, i.e. high-density cones. For all of the magnetic field cases analysed, the high-frequency spectra showed upper and lower sidebands centred around the driving frequency and at a separation equal to the instability frequency, 27.12 MHz ± f I kHz. Measurements of the perpendicular wavenumber would satisfy, for certain magnetic field strengths, the dispersion relation of both an electrostatic ion cyclotron wave (ICW) and of an ion acoustic wave. It is hypothesised that the observed low-frequency wave could be an acoustic-like instability propagating perpendicular to the magnetic field, which develops as an ICW at some magnetic field strengths. From the data collected, it is suggested that the high-frequency sidebands may be caused by modulation of the low-frequency wave.

Design and Characterization of a Novel Core-Shell Nano Delivery System Based on Zein and Carboxymethylated Short-Chain Amylose for Encapsulation of Curcumin.

Curcumin is a naturally occurring hydrophobic polyphenolic compound with a rapid metabolism, poor absorption, and low stability, which severely limits its bioavailability. Here, we employed a starch-protein-based nanoparticle approach to improve the curcumin bioavailability. This study focused on synthesizing nanoparticles with a zein "core" and a carboxymethylated short-chain amylose (CSA) "shell" through anti-solvent precipitation for delivering curcumin. The zein@CSA core-shell nanoparticles were extensively characterized for physicochemical properties, structural integrity, ionic stability, in vitro digestibility, and antioxidant activity. Fourier-transform infrared (FTIR) spectroscopy indicates nanoparticle formation through hydrogen-bonding, hydrophobic, and electrostatic interactions between zein and CSA. Zein@CSA core-shell nanoparticles exhibited enhanced stability in NaCl solution. At a zein-to-CSA ratio of 1:1.25, only 15.7% curcumin was released after 90 min of gastric digestion, and 66% was released in the intestine after 240 min, demonstrating a notable sustained release effect. Furthermore, these nanoparticles increased the scavenging capacity of the 1,1-diphenyl-2-picrylhydrazyl (DPPH•) free radical compared to those composed solely of zein and were essentially nontoxic to Caco-2 cells. This research offers valuable insights into curcumin encapsulation and delivery using zein@CSA core-shell nanoparticles.

A large population of neutron star low-mass X-ray binaries with long outburst recurrence time?

ABSTRACT Low-mass X-ray binaries (LMXBs) with neutron stars show quite different features that depend on the rate of mass transfer from the donor star. With a high transfer rate, the Z sources are in a persistent soft spectral state, and with a moderate transfer rate the transient Atoll sources have outburst cycles like the black hole X-ray binaries. The observations document very long outburst recurrence times for quite a number of sources. We follow with our computations the evolution of the accretion disc until the onset of the ionization instability. For sources with a low mass transfer rate, the accumulation of matter in the disc is essentially reduced due to the continuous evaporation of matter from the disc to the coronal flow. Different mass transfer rates result in nearly the same amount of matter accumulated for the outburst, which means that the outburst properties are similar for sources with short outburst cycles and sources with long outburst cycles, contrary to some expectations. Then, for systems with long recurrence time, less sources will be detected and the total population of LMXBs could be larger than it appears. This would relieve the apparent problem that the observed number of LMXBs as progenitors of millisecond pulsars (MSPs) is too small compared to the number of MSPs. Concerning the few quasi-persistent sources with year-long soft states, we argue that these states are not outbursts, but quasi-stationary hot states as in Z sources.

Influence of the Dufour effect on striations formation in radio-frequency discharges

In recent years, interest in striation phenomena in radio frequency (rf) discharges has risen due to the availability of new experimental data and the implementation of new computational models. Depending on the conditions, different mechanisms of discharge striations are realized. These are the ionization instability, the instability due to the electron attachment to electronegative gases, or the instability due to thermoelectric transport. Although the first two mechanisms were modeled quite extensively in recent years, the understanding of the influence of the Dufour effect originating from plasma density gradients on the stability of radio frequency discharges in long tubes remains poor. In this paper, the influence of this mechanism on the longitudinal striations of radio frequency discharge is presented using a one-dimensional model of argon discharge driven with rf excitation under intermediate pressure conditions of 0.5 Torr. It is found that striation formation is sensitive to the value of the thermoelectric heat transport coefficient in the low electron temperature range. The critical value of this coefficient necessary for the instability onset is derived using the linear stability analysis.

Transient striations in an inductively coupled plasma during E-to-H transitions

Abstract Azimuthal transient striations are reported for inductively coupled Ar plasma during E-to-H transition at 200 mTorr. In this transient process, the number of striations increases with time, and striations ultimately disappear when the H mode is reached. An integrated model is developed to investigate the mechanism of this phenomenon. This integrated model incorporates a one-dimensional time-dependent fluid model with a perturbation analysis, as well as a circuit model for power coupling with the external radio-frequency driving source. Based on this integrated model, the development of striations is proposed to be a consequence of ionization instability due to the variation in the electron energy distribution function. The model results for the temporal evolution of the number of striations are in good agreement with the observed data.

Properties and characteristics of the nanosecond discharge developing at the water–air interface: tracking evolution from a diffused streamer to a spark filament

The characteristics of nanosecond discharge propagating along the water–air interface in a unique dielectric-barrier discharge (DBD)-like configuration with coplanar electrodes submerged in deionised (DI)/tap water are studied by combining ultrafast imaging and emission spectra with electrical characteristics. Time-resolved images provide a clear signature of streamer channels excited on the water surface at either side of the blade (insulated plastic separating the anode/cathode) and propagating perpendicularly away from it towards the anode/cathode with different velocities. Later on, the streamer channels convert into a few discrete and bright discharge channels due to ionisation instability (spark phase). There is no distinctive dependence on water conductivity in the streamer phase, as the optical emission spectroscopy and images of discharges only showed an increase of the luminosity and no significant changes in morphology. However, in the spark phase, more numerous, brighter, and thicker filaments form in tap water. The time-resolved emission spectra reveal the dominance of the first and second positive system of N2 molecular bands in the streamer phase, followed by the appearance of atomic lines of hydrogen, nitrogen, and oxygen in the spark phase. The emission spectra are utilised to estimate several important parameters (gas temperature, reduced electric field ( E/N ), and electron density ( ne )). The streamer phase is characterised by a low gas temperature and a peak E/N amplitude between 700 and 850 Td. On the other hand, the subsequent spark phase is characterised by a gas temperature of ∼400/1100 K and a free electron density up to ne∼1017 –1018 cm−3 in DI/tap water.

Trivelpiece–Gould modes and low-frequency electron–ion instability of non-neutral plasma

The frequency spectra of the Trivelpiece–Gould modes of a waveguide partially filled with non-neutral plasma are determined numerically by solving the dispersion equation. The modes having azimuthal number $m = 1$ are considered. The results are presented for the entire acceptable range of electron densities, magnetic field strengths, for different values of the charge neutralization coefficient. The Cherenkov resonance condition of an ion with a diocotron mode having a finite value of the longitudinal wave vector was studied. The characteristics of resonant low-frequency electron–ion instability caused by relative azimuth motion of electrons and ions in crossed fields and by the anisotropy of the distribution function of ions are discussed. Ions are created by ionization of residual gas in the plasma volume. Due to the anisotropy, instability occurs not only in the vicinity of the resonance, but also outside it. For typical values of plasma parameters in experiments, estimations of the frequency growth rate are given. A conclusion is drawn that this instability can be the cause of the low-frequency oscillations observed in linear devices with non-neutral plasma produced in an electron beam channel.

2D kinetic simulations of whistler wave generation by nonlinear scattering of lower-hybrid waves in turbulent plasmas

Turbulent plasmas in space, laboratory experiments, and astrophysical domains can often be described by weak turbulence theory, which can be characterized as a broad spectrum of incoherent interacting waves. We investigate a fundamental nonlinear kinetic mechanism of weak turbulence that can explain the generation of whistler waves in homogeneous plasmas by nonlinear scattering of short wavelength electrostatic lower-hybrid (LH) waves. Two particle-in-cell (PIC) simulations with different mass ratios in two dimensions (2D) were performed using a ring ion velocity distribution to excite broadband LH waves. The wave modes evolve in frequency, and wavenumber space such that the LH waves are converted to whistler waves. The simulations show the formation of quasi-modes, which are low-frequency density perturbations driven by the ponderomotive force due to the beating of LH and whistler waves. These low-frequency oscillations are damped due to resonant phase matching with thermal plasma particles. By comparing the phase and thermal speeds, we confirm the nonlinear scattering mechanism and its role in the 2D evolution of the ring ion instability. Although the nonlinear scattering is theoretically slower in 2D than in 3D due to the absence of the vector nonlinearity, these simulations show that quasi-modes are an important diagnostic for nonlinear landau damping in PIC simulations that has not been utilized in the past. The nonlinear scattering mechanism described here plays an important role in the generation of whistler waves in active experiments, which will be experimentally studied in the upcoming Space Measurement of a Rocket Release Turbulence experiment.

A study on the photophysical properties of strong green-fluorescent N-doped carbon dots and application for pH sensing

Color tuneable effective pH sensor in both acidic and alkaline medium is important for environment and bioanalytical purpose. In this report, natural biomass derived N-doped fluorescent carbon dots are utilized as pH sensor. The fast microwave irradiation method was employed for synthesis using natural sweet lime juice extract. Ethylenediamine (EDA) was used for nitrogen doping with different amounts. The prepared N-doped carbon dots are comprehensively studied by various characterization methods to analyse the effect of dopant concentrations on photophysical and luminescence properties. Improved thermal stability from 900 °C to 1000 °C with EDA content is observed. The fluorescence spectra of prepared N-doped carbon dots exhibited stable green emission with high quantum yield 83 % under ultraviolet and 440 nm irradiation wavelengths for an optimal concentration of EDA. The color of emission confirmed by CIE plot and about 3.47 ns decay time is found by PL decay curve. The anti-photo bleaching ability and good photostability for 10 days are found. The prepared N-doped carbon dots exhibit high ionic stability and bio compatibility. Further, pH dependent color tuneable (green to yellow) emission spectra of prepared N-doped carbon dots displayed high fluorescence in acidic medium at pH -5. Although, emission was quenched and red shifted in alkaline medium. The effective pH-sensitivity, and good reversibility of fluorescent N-doped carbon dots samples were tested with real water samples having different pH values. The reasonable mechanism is discussed. It depicts the prepared N-doped carbon dots have potential to serve as pH sensor for physiochemical and bioanalytical measurements.

High-speed imaging reveals the dynamics of the initiation and subsequent evolution of a nanosecond discharge propagating along the air–water interface

A nanosecond DBD-like discharge in a coplanar electrode configuration propagating along the water–air interface is an efficient source of reactive species to produce plasma-activated water. In this letter, we report on the mechanism of the discharge onset as well as on further developments over hundreds of nanoseconds. We combined ultrafast optical imaging with electrical characteristics to capture basic morphological imprints of individual discharge phases occurring during a single discharge event with high temporal resolution. We show that during the first nanoseconds, a diffuse bi-directional ionizing avalanche expands over the liquid surface at high speed (>5 105 m s−1). Later, discrete plasma filaments form from the diffuse plasma due to an ionization instability. The filaments, during their subsequent elongation (∼2 105 m s−1), retain the diffuse plasma at both ends. The filaments re-ignite in the same positions on the liquid surface over several successive (mainly capacitive) current pulses (∼1 μs apart), which result from discontinuities in the driving voltage.

Electromagnetic particle-in-cell simulation on self-induced magnetic field by hollow cathode discharge

Strong electron current density exits in hollow cathodes, but former numerical studies tend to only consider its electrostatic aspect and ignore its electromagnetic (EM) nature, due to the complex physics and the large computational cost. Among all the EM effects in hollow cathodes, the azimuthal magnetic field induced by the electron current plays the key role. In this work, for the first time fully kinetic particle-in-cell simulations are conducted to study the induced magnetic field and relevant EM effects in hollow cathodes. It is found that the electron–ion instability could cause a significant drop of the induced magnetic field in a fraction of nanosecond. When the magnitude of the induced magnetic field is strong, its perturbation would disturb the electron current density, and these mechanisms can only be captured by EM simulations.

Observations and Modeling of Unstable Proton and α Particle Velocity Distributions in Sub-Alfvénic Solar Wind at Parker Solar Probe Perihelia

Past observations show that solar wind (SW) acceleration occurs inside the sub-Alfvénic region, reaching the local Alfvén speed at typical distances ∼10–20 solar radii (R s ). Recently, Parker Solar Probe (PSP) traversed regions of sub-Alfvénic SW near perihelia in encounters E8–E12 for the first time, providing data in these regions. It became evident that the properties of the magnetically dominated SW are considerably different from the super-Alfvénic wind. For example, there are changes in the relative abundances and drift of α particles with respect to protons, as well as in the magnitude of magnetic fluctuations. We use data of the magnetic field from the FIELDS instrument, and construct ion velocity distribution functions (VDFs) from the sub-Alfvénic regions using Solar Probe ANalyzer for Ions data, and run 2.5D and 3D hybrid models of proton-α sub-Alfvénic SW plasma. We investigate the nonlinear evolution of the ion kinetic instabilities in several case studies, and quantify the transfer of energy between the protons, α particles, and the kinetic waves. The models provide the 3D ion VDFs at the various stages of the instability evolution in the SW frame. By combining observational analysis with the modeling results, we gain insights on the evolution of the ion instabilities, the heating and the acceleration processes of the sub-Alfvénic SW plasma, and quantify the exchange of energy between the magnetic and kinetic components. The modeling results suggest that the ion kinetic instabilities are produced locally in the SW, resulting in anisotropic heating of the ions, as observed by PSP.

Detection of Extreme Acidity Based on Carbon Dots: One‐Step Gram‐Scaled Syntheses, Ratiometric Emission Photoluminescent Probe, and Hand‐Held Visual Detection

AbstractIt is a significant challenge to develop acidity probes suitable for use in extremely acidic conditions, especially to achieve real‐time on‐site detection. In this work, carbon dots (CDs) are synthesized on a gram‐scale under mild conditions using 3‐phenylpropionaldehyde as precursors. The CDs have excellent robustness, showing distinguished anti‐photobleaching and ionic stability. Dramatically, a visual transition of the fluorescent color of CDs from cyan to orange is observed when the concentration of H+ ([H+]) increased under high acidity conditions, owing to the generation of another emission peak in the red‐light region. Taking advantage of the optical properties, CDs are designed as a ratiometric sensing platform for the detection of extreme acidity. Furthermore, the platform for [H+] possesses high selectivity and excellent anti‐interference capability. In extremely acidic wastewater, I595 nm/I480 nm and [H+] maintain a very good linear relationship (R2 = 0.996). Moreover, a smartphone is employed to obtain the red‐green‐blue (RGB) values of the samples to realize hand‐held detection. By measuring the R/G, the platform exhibits ultrasensitive recognition of [H+] in the range of 1–9 mol L−1 with R2 of 0.992. This work paves an avenue for the design of rapid and on‐site CDs based sensors for critical environmental applications.