Broad pH Range Research Articles

The Swiss Army Knife of Electrodes: Pillar[6]arene-Modified Electrodes for Molecular Electrocatalysis Over a Wide pH Range.

Molecularly-modified electrode materials that maintain stability over a broad pH range are rare. Typically, each electrochemical transformation necessitates a specifically tuned system to achieve strong binding and high activity of the catalyst. Here, we report the functionalisation of mesoporous indium tin oxide (mITO) electrodes with the macrocyclic host molecule pillar[6]arene (PA[6]). These electrodes are stable within the pH range of 2.4-10.8 and can be equipped with electrochemically active ruthenium complexes through host-guest interactions to perform various oxidation reactions. Benzyl alcohol oxidation serves as a model reaction in acidic media, while ammonia oxidation is conducted to assess the systems performance under basic conditions. PA[6]-modified electrodes demonstrate catalytic activity for both reactions when complexed to different guest molecules and can be reused by reabsorption of the catalyst after its degradation. Furthermore, the system can be employed to perform subsequent reactions in electrolyte with varying pH, enabling the same electrode to be utilised in multiple different electrocatalytic reactions.

The Swiss Army Knife of Electrodes: Pillar[6]arene‐Modified Electrodes for Molecular Electrocatalysis Over a Wide pH Range

AbstractMolecularly‐modified electrode materials that maintain stability over a broad pH range are rare. Typically, each electrochemical transformation necessitates a specifically tuned system to achieve strong binding and high activity of the catalyst. Here, we report the functionalisation of mesoporous indium tin oxide (mITO) electrodes with the macrocyclic host molecule pillar[6]arene (PA[6]). These electrodes are stable within the pH range of 2.4–10.8 and can be equipped with electrochemically active ruthenium complexes through host–guest interactions to perform various oxidation reactions. Benzyl alcohol oxidation serves as a model reaction in acidic media, while ammonia oxidation is conducted to assess the systems performance under basic conditions. PA[6]‐modified electrodes demonstrate catalytic activity for both reactions when complexed to different guest molecules and can be reused by reabsorption of the catalyst after its degradation. Furthermore, the system can be employed to perform subsequent reactions in electrolyte with varying pH, enabling the same electrode to be utilised in multiple different electrocatalytic reactions.

Synthetic Control of Water-Stable Hybrid Perovskitoid Semiconductors.

Hybrid metal-halide perovskites and their derived materials have emerged as the next-generation semiconductors with a wide range of applications, including photovoltaics, light-emitting devices, and other optoelectronics. Over the past decade, numerous single-crystalline perovskite derivatives have been synthesized and developed. However, the synthetic methods for these derivatives mainly rely on acidic crystallization conditions. This approach leads to crystals comprising metal halide building blocks, which show problematic stability when directly exposed to water. In this study, a methodology is developed for synthesizing hybrid metal-halide compounds using lead iodide and the zwitterionic bifunctional molecule cysteamine (CYS), to form various perovskitoid structures under a broad pH range. Interestingly, the different pH conditions alter the coordination environment of lead halides, leading to lead-sulfide and lead-nitride covalent bond formation. This modification significantly enhances their stability when in direct contact with water, lasting for months. Photoluminescence measurements and first principal density functional theory (DFT) calculations reveal that the perovskitoids synthesized under basic and acidic pH conditions exhibit a direct bandgap nature, while those synthesized under neutral conditions display an indirect bandgap. This approach opens new avenues for manipulating synthetic methods to develop water-stable hybrid semiconductors suitable for a wide range of applications, such as solid-state light emitters.

Reactive Fluorescent and Colorimetric Probe for Highly Selective and Sensitive Detection of Hg2+ in Real Water Samples.

Construction of efficient chemosensors for highly specific and sensitive detection of mercury ions remains a great challenge. In this work a highly selective and sensitive probe CY was designed and synthesized by using coumarin fluorophore as the matrix and thioacetal moiety as the reactive recognition site for Hg2+. By virtue of the thiophilicity of Hg2+, probe CL could be hydrolyzed to deprotect and the thioacetal was transformed to the acyl group after the addition of Hg2+, the blue-green fluorescence was quenched and meanwhile the solution changed from light green to yellow. The detection limit of probe CY for Hg2+ was as low as 6.8 nM, and it could completely react with Hg2+ within 3min. Moreover, probe CY exhibited good resistance against interference from competitive metal ions and biothiols, high stability in pH 1-11 and applicability for fluorogenic and chromogenic dual-modal detection of Hg2+ in real water samples over a broad range of pH 5-10.

Polyethyleneimine assisted zeolitic imidazolate frameworks foam embed silver to enhance the uranium recovery from seawater

The powder structure, poor surface wettability and biofouling significantly limited the application potential of ZIFs (zeolitic imidazolate frameworks) in uranium extraction from seawater. Herein, a superhydrophilic polyethyleneimine assisted zeolitic imidazolate frameworks foam embed silver (CPEZ8A) was successfully prepared by simple chemical cross-linking and in-situ growth methods to explore the effects of hydrophilic matrix and silver antimicrobial agent on the uranium adsorption properties of ZIFs materials. The mechanical property and water contact angle test of CPEZ8A foam were performed to confirm its higher compression stress (with 1.314 MPa) and surface superhydrophilic. Moreover, CPEZ8A foam displayed an excellent resistance to biological attachment after 7 days in algae solution. Importantly, CPEZ8A showed the maximum U (VI) uptake capacity (775.19 mg/g) with 4.37 times of pure ZIF-8 at nearly seawater pH and retained relative high U-uptake amount during the broad pH range (4.0–9.0). Ion competition experiments were also investigated to verify the CPEZ8A foam excellent selectivity (Kd = 15,072.1 mL/g). Notably, the removal rate of CPEZ8A foam reach 81.31 % in natural seawater and remain nearly 80 % in simulated contaminated seawater. Therefore, this work provides an effective strategy to develop highly efficient ZIFs adsorbents for uranium capture.

Co-N3 site activated peroxymonosulfate for rapid degradation of ciprofloxacin: Synergistic effect of free radicals and nonfree radicals

Nitrogen-doped metal-organic framework (MOFs)-derived carbon materials (denoted as Co-MOF-74@N-T-x) were successfully fabricated by calcinating Co-MOF-74, utilizing the green precursor of melamine. Among these materials, Co-MOF-74@N-500-2 demonstrated superior catalytic performance in activating peroxymonosulfate (PMS), achieving over 95 % degradation of ciprofloxacin (CIP) within 15 min, with a rate constant that was 1.25 times greater than that of Co-MOF-74-500. The primary active species identified in this study were sulfate radicals (SO4•−) and singlet oxygen (1O2), with the latter playing an important role in the degradation of CIP in the Co-MOF-74@N-500-2/PMS system. Theoretical calculations confirmed that the enhanced catalytic activity primarily stemmed from the Co-N3 configuration, which was more effective in activating PMS than the other configurations were. Co-MOF-74@N-500-2/PMS showed excellent performance in oxidizing CIP across a broad pH range (3.0–9.0) and demonstrated stability over five cycles, along with impressive degradation performance capabilities for a wide range of pollutants including metronidazole (MNZ), oxytetracycline (OTC), nitrofurantoin (FNT), methylene blue (MB), and acid orange (OG). This study presents a viable strategy for developing efficient and durable catalytic systems aimed at degrading organic pollutants via PMS.

CaCO3-activited N-doped diatom biochar for the degradation of tetracycline

In this study, a N-doped diatom biochar (DBC) was prepared by one-step pyrolysis, where CaCO3 formed by marine diatom-mediated calcification was employed as an activator. Due to the activation effect of CaCO3, the specific surface area of the obtained DBC increased by more than 10 times, and the nitrogen presented as pyrrolic nitrogen (58.9%), pyridinic nitrogen (29.7%), and graphitic nitrogen (11.4%) in the DBC. In addition, the effects of important parameters and co-existing ions on the catalytic decomposition of tetracycline (TC) by DBC were investigated by using TC as a typical pollutant and PDS as an oxidant. The DBC/PDS system exhibited high activity over a broad pH range. Through radical scavenging experiments, electron spin resonance, and electrochemical results analysis, it was found that the degradation of TC in the system included both radical and nonradical pathways, and the most dominant reactive species was 1O2. Furthermore, the surficial reactive complexes formed by PDS on the catalysts also played an important role in attacking the adsorbed TC molecules. This study proposes an eco-friendly and economical technique to construct a clean advanced oxidation process capable of treating TC wastewater by utilizing the native biomass of diatom as a metal-free and efficient biochar catalyst while simultaneously reducing the use of chemical reagents.

Comparative analysis of cotton oil and fuel oil as collectors in hard coal flotation: Toward sustainable mining practices

ABSTRACT This study investigates cotton oil as an environmentally friendly alternative to fuel oil in the flotation of hard coal from the Zonguldak Kozlu Region, Türkiye. We compared their performance across various operational parameters using a Denver-type flotation machine. Results showed that cotton oil achieved superior combustible recovery in most scenarios. At 1000 g/t, cotton oil achieved 97% combustible recovery compared to fuel oil’s 90% at 2000 g/t. Cotton oil maintained high recovery (94–95%) over a broader pH range (2–10) compared to fuel oil’s stable 90% from pH 2–8. However, fuel oil demonstrated better ash rejection, achieving 50% rejection at 2% solids compared to cotton oil’s 36%. Both oils performed optimally at pH 8.25 and 10% solid ratio. Cotton oil maintained 93% recovery at 1050 rpm compared to fuel oil’s 89% and exhibited less sensitivity to frother concentration. FTIR and zeta potential analyses revealed distinct interaction mechanisms, with cotton oil showing stronger adsorption on coal surfaces. This research contributes to developing sustainable practices in coal beneficiation, highlighting the trade-offs between combustible recovery and ash rejection when choosing between these collectors for industrial applications.

Mechanism of Enhanced Fluoride Adsorption Using Amino-Functionalized Aluminum-Based Metal–Organic Frameworks

Due to the increasing fluoride concentrations in water bodies, significant environmental concerns have arisen. This study focuses on aluminum-based materials with a high affinity for fluorine, specifically enhancing metal–organic frameworks (MOFs) with amino groups to improve their adsorption and defluorination performance. We systematically investigate the factors influencing and mechanisms governing the adsorption and defluorination behavior of amino-functionalized aluminum-based MOF materials in aqueous environments. An SEM, XRD, and FT-IR characterization confirms the successful preparation of NH2-MIL-101 (Al). In a 10 mg/L fluoride ion solution at pH 7.0, fluoride ion removal efficiency increases with the dosage of NH2-MIL-101 (Al), although the marginal improvement decreases beyond 0.015 g/L. Under identical conditions, the fluoride adsorption capacity of NH2-MIL-101 (Al) is seven times greater than that of NH2-MIL-101 (Fe). NH2-MIL-101 (Al) demonstrates effective fluoride ion adsorption across a broad pH range, with superior fluoride uptake in acidic conditions. At a fluoride ion concentration of 7 mg/L, with 0.015 g of NH2-MIL-101 (Al) at pH 3.0, adsorption equilibrium is achieved within 60 min, with a capacity of 31.2 mg/g. An analysis using adsorption isotherm models reveals that the fluoride ion adsorption on NH2-MIL-101 (Al) follows a monolayer adsorption model, while kinetic studies indicate that the predominant adsorption mechanism is chemical adsorption. This research provides a scientific basis for the advanced treatment of fluoride-containing wastewater, offering significant theoretical and practical contributions.

Characterization of argonaute nucleases from mesophilic bacteria Pseudobutyrivibrio ruminis

Mesophilic Argonautes (Agos) from microbial resources have received significant attention due to their potential applications in genome editing and molecular diagnostics. This study characterizes a novel Ago from Pseudobutyrivibrio ruminis (PrAgo), which can cleave single-stranded DNA using guide DNA (gDNA). PrAgo, functioning as a multi-turnover enzyme, effectively cleaves DNA using 5′-phosphate gDNA, 14–30 nucleotides in length, in the presence of both Mn2+ and Mg2+ ions. PrAgo demonstrates DNA cleavage activity over a broad pH range (pH 4–12), with optimal activity at pH 11. As a mesophilic enzyme, PrAgo cleaves efficiently DNA at temperatures ranging from 25 to 65 °C, particularly at 65 °C. PrAgo does not show strong preferences for the 5′-nucleotide in gDNA. It shows high tolerance for single-base mismatches, except at positions 13 and 15 of gDNA. Continuous double-nucleotide mismatches at positions 10–16 of gDNA significantly reduce cleavage activity. Furthermore, PrAgo mediates DNA-guided DNA cleavage of AT-rich double stranded DNA at 65 °C. Additionally, molecular dynamic simulations suggest that interactions between the PAZ domain and different nucleic acids strongly influence cleavage efficiency. These findings expand our understanding of Protokaryotic Agos and their potential applications in biotechnology.Graphical

Structural dissection of the CMP-pseudaminic acid synthetase, PseF.

Pseudaminic acid is a non-mammalian sugar found in the surface glycoconjugates of many bacteria, including several human pathogens, and is a virulence factor thought to facilitate immune evasion. The final step in the biosynthesis of the nucleotide activated form of the sugar, CMP-Pse5Ac7Ac is performed by a CMP-Pse5Ac7Ac synthetase (PseF). Here we present the biochemical and structural characterization of PseF from Aeromonas caviae (AcPseF), with AcPseF displaying metal-dependent activity over a broad pH and temperature range. Upon binding to CMP-Pse5Ac7Ac, AcPseF undergoes dynamic movements akin to other CMP-ulosonic acid synthetases. The enzyme clearly discriminates Pse5Ac7Ac from other ulosonic acids, through active site interactions with side-chain functional groups and by positioning the molecule in a hydrophobic pocket. Finally, we show that AcPseF binds the CMP-Pse5Ac7Ac side chain in the lowest energy conformation, a trend that we observed in the structures of other enzymes of this class.

Photophysiological response of glacier ice algae to abiotic stressors

The glacier ice algae Ancylonema alaskanum and Ancylonema nordenskiöldii grow in harsh dynamic environments on bare ice surfaces. In these environments, they contribute to the continuous darkening of the ice surface, which in turn accelerates the ice melt. However, investigation into their adaptation and resilience in these environments is necessary in order to understand their robustness and potential for increasing the intensity of blooms. In this study, it was examined how variations in environmental parameters such as pH, salinity, light and temperature impacted the photophysiology of the glacier ice algae during a bloom in Greenland. Through in situ incubations and pulse-amplitude-modulation (PAM) fluorometric measurements, the photophysiological responses of algal cells were assessed. Results suggest that light intensity significantly influences glacier ice algae photophysiology, with cells exhibiting better performance (in terms of a higher theoretical maximum light coefficient and maximum quantum efficiency) under lower light intensity. Moreover, while light emerges as the primary driver of photophysiology, glacier ice algae demonstrate tolerance to a broad range of pH and temperatures four times higher than those experienced during Greenland’s summer.

Silver carp swim bladder collagen derived from deep eutectic solvents: Enhanced solubility against pH and NaCl stresses

Deep eutectic solvents (DESs) are renowned in chemical and food industries for their eco-friendly extraction efficacy. Silver carp swim bladders, a collagen-rich byproduct of surimi production, are underutilized, resulting in considerable protein waste. Traditionally, collagen extraction has relied on harsh acids, contributing to environmental pollution and producing collagens with limited solubility, thus constraining their applications. This study evaluated DESs compared to conventional acids in extracting collagen, focusing on structural and solubility variations. Notably, urea-based DESs (urea-lactic acid: U-LA, 1:10, w/v) achieved the highest hydroxyproline recovery rates (∼ 94 %), comparable to acetic acid (AA, 1:20, w/v), but with half the solid-liquid ratio. Unlike acid-extracted collagen, which preserved the triple-helical structure, urea-based DESs partially disrupted this configuration by reducing intramolecular hydrogen bonding within collagen. However, these solvents simultaneously increased intermolecular hydrogen bonding. This alteration significantly enhanced collagen's solubility, maintaining over 60 % across a broad pH range (1−10) and various NaCl concentrations (0–6 %, w/v). Furthermore, urea-acetic acid (U-AA) extracted collagen exhibited the highest maximum transition temperature (solid state, Tmax = 101.94 °C) and gel strength (165 g). The findings suggest that urea-based DESs not only enhance collagen recovery rates but also its solubility and gelation properties, broadening its potential applications in cosmetics, food products, and biomaterials.

Oxidative stability of chelated Sn(II)(aq) at neutral pH: The critical role of NO3- ions.

Tin(II) compounds are versatile materials with applications across fields such as catalysis, diagnostic imaging, and therapeutic drugs. However, oxidative stabilization of Sn(II) has remained an unresolved challenge as its reactivity with water and dioxygen results in loss of functionality, limiting technological advancement. Approaches to slow Sn(II) oxidation with chelating ligands or sacrificial electron donors have yielded only moderate improvements. We demonstrate here that the addition of nitrate to pyrophosphate-chelated Sn(II)(aq) suppresses Sn(II) oxidation in water across a broad pH range. Evidence of hydroxyl radical concentration reduction and detection of a radical nitrogen species that only forms in the presence of chelated Sn(II) point to a radical-based reaction mechanism. While this chemistry can be broadly applied, we present that this approach maintains Sn(II)'s antibacterial and anti-inflammatory efficacies as an example of sustained oral chemotherapeutic functionality.

Zein-cyclodextrin complex used to prepare high internal phase pickering emulsions with various oil phases

Biobased solid particles for stabilizing high internal phase emulsions (HIPEs) are widely used in food and cosmetics industries. This study report a kind of zein-cyclodextrin complex particles which could HIPEs with various oil phases (log P values: 1.14–9.26), showcasing their wide applicability across different oil types. This versatility due to the slight differences (6–8°) in the three-phase contact angles for different oils. Furthermore, the complex particles showed a marked improvement in emulsification performance, as evidenced by their significantly higher diffusion rates (7–15 times faster) and reorientation speeds (2–5 times faster) at the oil-water interface. Moreover, the emulsions prepared were stable across a broad pH range (3–9), successfully addressing the common stability challenges associated with protein-based emulsifiers near their isoelectric points. Therefore, these complex particles have great potential in cosmetics, waste oil treatment and food field, such as multifunctional 3D bioprinting ink.

Construction of a multiple reactive species-mediated Co9S8/NBC-PMS Fenton-like system for tetracycline degradation with broadened adaptability to water background

A Fenton-like system based on peroxymonosulfate (PMS) oxidant has high potential for antibiotic degradation, However, various complex water background factors, including pH, coexisting ions, and dissolved organic matter, can adversely affect degradation efficiency. This work constructed a PMS oxidative Fenton-like system activated by cobalt polysulfide/N-doped biochar composite (Co9S8/NBC) for the degradation of tetracycline (TC) and achieving approximately 99 % removal of TC. Furthermore, the removal efficiency was maintained above 90 % across a broad pH range (3−11), in the presence of various coexisting anions (Cl−, NO3− and CO32−), even at high concentrations of humic acid. The characterization of Co9S8/NBC through various techniques confirmed that Co9S8 nanoparticles were uniformly loaded within the porous NBC structure. Electron paramagnetic resonance and reactive oxygen species (ROSs) quenching experiment revealed that the effectiveness of TC degradation in the Co9S8/NBC/NBC-PMS system arises from the cooperation of radical and non-radical species rather than the single mechanism. Moreover, the analysis of the contribution ratios of ROSs to TC degradation indicates that the contribution of non-free radicals exceeds that of free radicals, and it is capable of adapting to changes in pH. The characterization of the post-reaction catalyst suggested that Co9S8 and NBC synergistically participated in the activation of PMS. Moreover, the practical examination proved that the disabled Co9S8/NBC catalyst can recover the catalytic activity via a reheat treatment, the leaching concentration of Co ions was lower than the emission limit of China. The river water and lake water as the matrix water have little negative impact on the degradation of TC. The Co9S8/NBC-PMS system is expected to provide a practical pathway for the treatment of antibiotic wastewater.

Application of a laccase-catalyzed oxidative coupling for the removal and detoxification of typical flotation reagent salicylhydroxamic acid

Residual organic flotation reagents in mineral processing wastewater (MPW) can pose environmental hazards and hinder the sustainable development of the mining industry. Laccase as a versatile biocatalyst can eliminate various recalcitrant contaminants from the environment, but its potential applications for the removal and detoxification of organic flotation reagents have until now been overlooked. Herein, the influence of superparamagnetic immobilized laccase (SPM-IMLac) on the enzymatic removal of salicylhydroxamic acid (SHA), a typical mineral flotation reagent, as well as the mechanism of this process have been explored for the first time. The results indicated that SPM-IMLac can effectively remove SHA over a broad pH range and this process follows the pseudo-first-order reaction kinetics. A methodology which combined high resolution mass spectrometry (HRMS) and a solid phase extraction (SPE) technique revealed that SPM-IMLac could catalyze a single-electron oxidation of SHA to generate self/cross-oligomers via radical-driven C-C and/or C-O-C covalent coupling pathways. The Vibrio fischeri bioluminescence inhibition assay and a total organic carbon (TOC) analysis corroborated that the SHA transformation was accompanied by detoxification and by a reduction in TOC of the reaction solution, the extent of which correlated with the extent of the oxidative coupling. Moreover, SPM-IMLac could be easily recovered and reused, while keeping its high removal efficiency of SHA in the actual MPW matrices. This study not only provides fascinating insights into the transformation mechanisms and environmental fate of SHA mediated by SPM-IMLac, but it also exploits a viable and sustainable approach for the remediation of organic flotation reagents-contaminated MPW.

Transforming waste to purity: 3D electro-Fenton process boosted with pistachio shell-derived iron-biochar electrode for methyl violet 2B dye catalytic removal

Traditional degradation methods with typical catalysts which have limited negatively charged surfaces are not effectively degrade cationic dyes. A multi-functional iron-biochar was prepared from waste pistachio shells (Fe@PSB) that offers enhanced dye removal due to abundance of negatively charged sites for the degradation of the carcinogenic dye known as methyl violet 2B (MV 2B) in a cutting-edge three-dimensional electrochemical Fenton system (3DEF) with graphite (GP) cathode and Titanium (Ti) anode (3DEF-Ti/GP). Catalytic properties of Fe@PSB were explored for MV 2B dye degradation at broad acidic pH range. At optimum operating conditions of the current of 2.0A, pH 5.0, and Na2SO4 dose of 0.2M, nearly 98.8% of 10mg/L MV 2B dye removal was attained in 60min of electrolysis time. Commercial particle electrodes did not perform as well for the MV 2B dye degradation. The catalytic mechanism of 3DEF-Ti/GP system was investigated by quenching experiments which revealed that the hydroxyl radical (•OH) was responsible for the oxidation of dye molecules. Fe@PSB significantly performed up to four successful cycles. Liquid chromatography-mass spectrometry analysis revealed that de-methylation was the primary degradation pathway. This unique approach not only valorizes agricultural waste but also paving the way for greener environmental solutions.

Two-step synthesis of ionic liquid demulsifiers for demulsification of water-in-oil emulsion

Stabilized water-in-oil emulsions present significant challenges for oil production. However, current demulsifiers often face limitations such as high demulsification temperatures, low efficiencies, and complex synthesis processes, making the resolution of this challenge a demanding task. In this study, we successfully synthesized two ionic liquid demulsifiers, PEDA-Br and GEDA-Br, employing a straightforward two-step procedure. The objective was to enable effective treatment of water-in-oil emulsions at low temperatures with high efficiency. The structure of the demulsifiers was characterized utilizing Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). Bottle tests were then conducted to evaluate their demulsification efficiency (DE) in water-in-oil (W/O) emulsions. The results demonstrated that GEDA-Br achieved a DE of 98.92 % at a concentration of 500 mg/L and a temperature of 50 °C after 2 h. Additionally, both PEDA-Br and GEDA-Br exhibited DE values exceeding 95 % at a salinity level of 10,000 mg/L, and both proved effective across a broad pH range of 4 to 12. These findings highlight their robust resistance to high salinity and both acidic and alkaline conditions. The study also examined the demulsification mechanism in terms of interfacial tension (IFT), elastic modulus of the interfacial film, three-phase contact angle (TCA), and microscopic observations. The excellent interfacial activity, ability to reduce interfacial tension, and electrostatic neutralization capability are responsible for its outstanding demulsification performance.

Facile Molecular-Level Refinements for Carbon Quantum Dots via Hydrogen-Bonding-Assisted Selective Isolation.

A novel method for synthesizing and refining high-purity carbon quantum dots (CQDs) using citric acid and diethylenetriamine as precursors is presented, achieved through molecular-level control by exploiting the differences in hydrogen-bonding strength. This process involves precipitation using melamine, extraction into ethanol, and encapsulation with (3-aminopropyl)triethoxysilane (APTES). The resulting APTES-encapsulated CQDs exhibited an enhanced color purity, higher photoluminescence quantum yield, and improved fluorescence stability over a broad pH range. Utilizing these well-defined high-purity CQDs with uniform surface states, it has been revealed that ferric ions are photochemically sensed through the inner filter effect (IFE) mechanism, while mercury ions are detected through the photoinduced electron transfer (PET) mechanism. The versatility of CQDs, coupled with our advanced refinement technology, is expected to contribute significantly to the development of advanced research applications, particularly in displays and sensors.