Sulfonic Groups Research Articles

A novel macromolecular flame retardant based on sulfonyl diphenol monomer for simultaneous fire safety, transparency and high performance of thin-walled polycarbonate

In order to further advance the development of transparency, fire safety, and high-performance thin-walled polycarbonate (PC), it is essential to avoid the negative impact of traditional flame retardants on the overall performance of PC. In this work, a new copolymer polycarbonate (ASPC) containing sulfonyl diphenol monomer was synthesized by interfacial polycondensation, and it was used as a flame retardant for PC. Due to the fact that the compounds containing sulfonic acid groups produced by the decomposition of ASPC in a high temperature environment promote the crosslinking and rearrangement of PC, the PC can generate a denser char layer during combustion, thus effectively preventing the exchange of heat and gas inside and outside the matrix. To addition of 20 wt% ASPC can make PC with a thickness of 1.5 mm to pass the UL 94 V-0 rating and LOI increased to 33.5 %. The peak of heat release rate (PHRR) and smoke produce rate (PSPR) of PC/ASPC-20 was decreased by 32.4 % and 38.4 %, respectively. More importantly, the addition of ASPC can delay the speed of flame spread, provide people with more escape time and reduce the fire hazard. Furthermore, the ASPC is good compatibility with PC due to the structural similarity between ASPC and PC. Therefore, PC/ASPC maintains the comparable transparency and tensile properties of PC. The transmittance of PC/ASPC-20 is 87.7 %, and the elongation at break is 32.5 % higher than that of PC. This work provides a new solution for the preparation of flame-retardant modification of transparent and thin-walled PC, and expands the application scope of PC composites.

Biomimetic Channels Design in Metal-Organic Framework Enabling Highly Lithium-Ion Conduction for Lithium-Metal Batteries.

Solid-state electrolytes (SSEs) based on metal-organic frameworks (MOFs) are an ideal material for constructing high-performance lithium metal batteries (LMBs). However, the low ion conductivity and poor interface contact (especially at low temperatures) still seriously hinder its further application. Herein, inspired by the Na+/K+ conduction in biology systems, a series (NH2, OH, NH-(CH2)3-SO3H)-modified MIL-53-X as SSEs is reported. These functional groups are similar to anions suspended in biological ion channels, partially repelling anions while allowing cations to be effectively transported through pore channels. Subsequently, MIL-53-X with hierarchical pore structure (H-MIL-53-X) is obtained by introducing lauric acid as a regulator, and then the effects of structural design and morphology control on its performance are explored. The conductivity of H-MIL-53-NH-SO3Li with multi-level pore structure and modified by sulfonic acid groups reached 2.2×10-3Scm-1 at 25°C, lithium-ion transference number of 0.78. Besides, the H-MIL-53-NH-SO3Li still has an excellent conductivity of 10-4Scm-1 at -40°C. Additionally, LiFePO4/Li batteries equipped with H-MIL-53-NH-SO3Li SSEs could operate stably for over 200 cycles at 0.1C. The strategy of combining structural and morphological design of MOFs with biomimetic ion channels opens new avenues for the design of high-performance SSEs.

The adsorption of cesium by sulfonic acid functionalized hollow mesoporous silica microspheres

With the development of nuclear industry, radioactive elements such as 137Cs put a threat on the water environment. It is a challenging task to remove the Cs+ in the nuclear wastewater. In the current study, we prepared a new Cs+-adsorbing material by introducing sulfhydryl group onto the surface of hollow mesoporous silica microspheres, then oxidizing the sulfhydryl group to sulfonic acid group. The obtained HMSS-SO3H material had an excellent adsorption capacity for Cs+ in the aqueous solution, with an adsorption capacity of 51.53 mg g−1 in 30 min. Characterization approaches, such as FT-IR and EDS, were used to confirm the result of modification. Adsorption experiments were carried out under. The influence of various parameters on the adsorption process was investigated under the conditions of changing pH, temperature, and time. The effect of competitive ions was also explored. The results indicated that the adsorption process followed the pseudo-second-order model and the main adsorption mechanisms are electrostatic interaction and coordination. The material had a best adsorption performance at a neutral pH. The adsorption process could well-fit the Langmuir's model, with a theoretical maximum adsorption capacity of 81.31 mg g−1. And the adsorption capacity was slightly affected by competing ions such as Mg2+ and Ca2+. The results indicate that the HMSS-SO3H prepared in this study is a promising adsorbent for Cs+, with the advantages of high adsorption capacity, fast adsorption rate and high selectivity.

Graphene/polyaniline waterborne composite coatings for metallic bipolar plates

Waterborne composite coatings were formulated for protection of metallic bipolar plates. The challenges lied in two aspects, one was the confliction between high electrical conductivity and good corrosion protection properties; the other was the water dispersibility of the constituent phases. Water-solubility of polyaniline (PANI) were controlled by adding polystyrene sulfonic acid during the polymerization of aniline. Graphene was functionalized by p-aminobenzoic acid and p-phenylenediamine to enhance the compatibility with PANI, while keeping the electrical conductivity of graphene at around 169 S/cm. Upon in-situ polymerization of the functionalized graphene/PANI composites, the electrical conductivity varied significantly from 41 S/cm to 91 S/cm with the surface functionality of graphene. The composite coatings were prepared thereafter with functionalized graphene/PANI/carbon black on the surface of 316 L stainless steel by centrifugal spraying coating. The interfacial contact resistance of the coatings reached 4 mΩ·cm2, comparable to Au coatings, but the corrosion current density was 4.37 μA/cm2 due to the existence of the hydrophilic groups in waterborne coatings, like amino groups and sulfonic acid groups. A post-treatment was carried out to consume some of the amino groups, so that the corrosion current density was decreased to 0.88 μA/cm2.

Porous polymeric materials prepared via pickering emulsion templating targeted as a bronsted acid catalyst in room-temperature biodiesel production

The present work is about preparing a set of magnetic macroporous polymers using the Pickering high internal phase w/o emulsions (HIPEs) templating method. The octyl-modified core-shell magnetic nanoparticles (Fe3O4@SiO2-Octyl) were used as a solid stabilizer and Span 80 surfactant to stabilize the HIPEs. The effect of Fe3O4@SiO2-Octyl content, Span 80 content, and molar ratio of styrene/divinylbenzene (St/DVB) on physical properties, morphology, pore size, and void size of the macroporous polyHIPEs was precisely evaluated. The optimized polyHIPE prepared by 2 wt% of Fe3O4@SiO2-Octyl nanoparticles, 9 wt% of Span 80, and St/DVB molar ratio of 8 with the porosity of 86±1.1 % and an average pore size of 4.1 µm was selected as catalyst support to functionalize with sulfonic acid groups. The resulting catalyst (polyHIPE–SO3H) showed excellent performance in reacting long-chain free fatty acids (FFA) with methanol to give fatty acid monoalkyl esters (FAMEs) at room temperature. In this way, the polyHIPE–SO3H was found to be very active and reusable in the mentioned process, giving high yields (∼92–98 %) of various biodiesel compounds under very mild reaction conditions and recycling in the next subsequent runs without significant loss of activity.

Cross-linked proton exchange membrane covalently bonded with silicotungstic acid for enhanced proton conductivity

Proton exchange membranes with cross-linked structures often showed excellent mechanical and chemical stability, but their water absorption and proton conductivity were restricted. This study reported a convenient and efficient thermal cross-linking reaction of sulfonic acid groups and benzene rings using dimethyl sulfoxide and sulfolane mixed solvents to prepare the membrane. To further illustrate, phenoxyphenyl-attached silicotungstic acid (POP-SiWA) was incorporated in the sulfonated poly(ether ether ketone) membrane and covalently bonded with the polymer by thermal cross-linking reaction. The immobilization ratio for the membranes prepared with 10∼30 wt% POP-SiWA addition was 88.0–63.7%. The modified membranes exhibited high hydrophilicity and improved proton conductivity under hydrated or low relative humidity conditions due to the strong acidity and water-retaining properties of silicotungstic acid. Specifically, the proton conductivity of the modified membrane with 30 wt% POP-SiWA reached 212 mS/cm. It exhibited a fuel cell power density of 629 mW/cm2 at 80 °C and 100% relative humidity, which were 1.90 and 2.67 times higher than the pristine membrane.

Building block design of thermally regenerable metal–organic framework composites for highly selective lithium adsorption

Crown ether-based organic lithium adsorbent has good stability for diverse lithium extraction scenarios, but hindering by its relatively low selectivity. Here, we report a building block design strategy for fabricating highly selective and thermally regenerable 12-crown-4 (12CE4) based lithium adsorbent. The synergistic coordination and ion-sieving blocks can sufficiently improve the ion selectivity and adsorption capacity of pNCE@MOF fabricated by copolymerizing thermosensitive segment and 12CE4 inside MOF. With the aid of synergistic coordination component of sulfonate group (SS), its Li+/Mg2+ selectivity increased from 12.9 to 21.8 (pNCE-SS@UiO-66) tested in 10,000 ppm salt solutions. Moreover, the 6.0 Å window of UiO-66 could successfully sieve hydrated Li+ (7.64 Å) and Mg2+ (8.56 Å), enhancing the selectivity 3.3 times from 5.1 for pNCE-SS@MOF-808 (10.0 Å) to 21.8. The adsorption capacity of pNCE-SS@UiO-66 was also optimized from 1.00 to 1.47 mmol·g−1. Furthermore, this material demonstrated a lithium selectivity of 11.5–19.8 in synthetic brines with a Mg/Li ratio of 1 to 0.1. Importantly, it could be fully regenerated in warm water at ≥ 40 °C. This work opens the door to constructing highly ion-selective functional materials via a modular method.

Saturation absorbed sodium benzenesulfonate as crystallization modulating additive for dendrite-free Zn anode

Aqueous Zn metal batteries face significant obstacles such as rampant Zn dendrite growth and side reactions besides their benefits. Adding trace amounts of organic additives in electrolyte is considered as an application strategy to achieve long cycling performance. In this study, sodium benzenesulfonate (SBS) composed of an electron-withdrawing sulfonate group and a benzene ring is introduced as a crystallization modulating additive into ZnSO4 solution. We find that the saturation absorption concentration of SBS plays a key role in realizing the uniform deposition of Zn metal anode. SBS is vertically adsorbed onto Zn surface, building a top-down internal electric field that promotes the three-dimensional diffusion of Zn2+. SBS shows a crystallization modulating behavior in terms of grain nucleation, grain morphology and crystal orientation. The well-tailored crystallization structure contributes to a uniform Zn metal deposition for long cycling, which improved from 300 to 4000 cycles with the addition of SBS. At the saturation concentration of SBS, the Zn||Zn symmetric cell shows a lifespan of over 2200 h at 1 mA cm−2. This work not only provides a new option for Zn metal batteries additives but also offers new insights into the function of electrolyte additives.

Mild and efficient approach to aromatic backbone cleavage using copper-lignosulfonate/hydrogen peroxide system

This study investigates the dual role of copper ions in catalysis and complexation during the oxidation of lignosulfonates with hydrogen peroxide (H2O2) under alkaline conditions. The presence of copper ions reduces partial oxidation by 86 % compared to H2O2 treatment alone, enhancing overall conversion efficiency to 63 % under increased oxidative conditions. Analyses reveal that copper-lignosulfonate complexes facilitate redox cycling and hydroxyl radical generation through interactions with H2O2, confirming copper’s dual functions. This mechanism mitigates the hindrance of sulfonic groups on hydroperoxide anions, leading to lignosulfonate degradation into dicarboxylic acids. These findings provide novel insights into the copper-lignosulfonate/H2O2 system, expanding the understanding of oxidative degradation mechanisms beyond traditional Fenton-like reactions. Furthermore, this system offers a simplified and efficient alternative for industrial applications, particularly in integration with the sulfite pretreatment process of woody biomass for producing valuable co-products.

Design of sulfonic group based hyper cross-linked polymer as adsorbent for efficient enrichment of endocrine disrupters

Design of sulfonic group based hyper cross-linked polymer as adsorbent for efficient enrichment of endocrine disrupters

Optimation of Fe3+ Ion Desorption Using Sulfonate Modified Silica Gel-GPTMS

Silica gel is one of the adsorbents widely used in adsorption, but silica gel has a low ability to absorb metals. Hence, modifications need to be made to improve it. Silica gel modified using sulfonate groups from monosodium salt compound of 4-amino-5-hydroxy-2,7-naphthalene disulfonic acid using GPTMS coupling compound for adsorption and desorption of Fe3+ ions by column method was carried out. The adsorption process of Fe3+ ions using silica gel-GPTMS-sulfonate has been carried out in previous studies and obtained an optimum state at pH 6 and a concentration of 20 ppm. After the adsorption process is carried out, the desorption process is continued with variations in the type of desorption eluent and concentration variations. The types of desorption agents are NaCl, CaCl2, HCl, and HNO3, with the optimum desorption agent being HNO3 with a release of 0.077517 mg of Fe3+ ions from 0.1587403 mg of Fe3+ ions absorbed and a desorption percentage of 48.83%. The concentration variations are 0.5 M, 1 M, 2.5 M, and 5 M, with an optimum concentration of 2.5 M HNO3 with a release of 0.098505 mg Fe3+ ions and a desorption percentage of 64.43%.

Evaluating Effects of Cerium Concentration and Water Content on Diffusivity of Cerium Ions in PEFC Using Molecular Dynamics Simulations

We investigated effects of cerium concentrations and water content on diffusivity of cerium ions in Nafion membrane. The diffusion coefficients of cerium ions were taken, and the structural features that could change diffusivity were analyzed. Results show that difference in concentrations in this study is independent of diffusivity. Although there was a slight difference in structure depending on the concentration, it was suggested that this depended on the initial position of the cerium ion. The diffusion of cerium ions was found to be greatly affected by water content. When water content is 3, cerium ions coordinate with sulfonic acid group because of luck of water around cerium ion. As water content increase, cerium ions are fully hydrated, and they may have high diffusivity. The growth of water clusters, which are the transport pathway for the ions, is also thought to be the cause of the significantly larger diffusion coefficient.

Supramolecular polymer cross-linking gel electrolyte for highly stable quasi-solid-state lithium metal batteries

Lithium (Li) metal batteries have the advantage of high energy density, but the Li dendrites risk piercing the separator and causing a short circuit in the battery. Replacing the liquid electrolytes with gel electrolytes is considered an effective strategy to solve the issues. Herein, a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel electrolyte, improved with multifunctional supramolecular polymer (MSP), was prepared to enhance the cycling stability and energy density of quasi-solid-state Li metal batteries. The MSP addictive constructs a cross-linked network structure with PVDF-HFP matrix and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) through hydrogen bonding, improving the mechanical strength of the composite gel electrolyte (PH-10%MSP-GE) to against the growth of Li dendrites. Moreover, the pre-lithiated sulfonic acid groups, conductive polyether groups of MSP, and the attraction of TFSI– anions, promote the Li-ion transportation of the composite gel electrolyte. Finally, the Li||Li symmetric cell cycle stably for over 450 h. The Li||LiFePO4 full cell demonstrates a high energy density and excellent cycling stability for over 600 cycles, with a capacity retention rate of up to 98.7%. This work provides valuable insights into the preparation of multifunctional composite gel polymer electrolytes and competitive quasi-solid-state Li metal batteries.

Effects of Ionomer Film Thickness and Water Content on Oxygen Permeation Properties of PEFC Cathode Catalyst

In order to promote the widespread use of Polymer Electrolyte Fuel Cell (PEFC), enhancing cell performance is necessary. One significant factor affecting cell performance is the oxygen permeability in the ionomer, which depends on its nano-scale structure. In this study, to investigate the relationship between structures of catalyst layers and cell performances, we analyzed the effects of film thickness and water content on the oxygen permeation properties of ionomer in the cathode catalyst layer of PEFC using molecular dynamics simulations. We constructed a system in which oxygen molecules permeated ionomer on a platinum (Pt) surface. We found that sulfonic acid groups have a significant effect on oxygen permeation in low water content conditions.

Al(SO4)(OH)·5H2O Stemming from Complexation of Aluminum Sulfate with Water-Soluble Ternary Copolymer and further Stabilized by Silica Gel as Effective Admixtures for Enhanced Mortar Cementing.

A water-soluble ternary copolymer bearing carboxyl, sulfonic, and amide functional groups was synthesized using ammonium persulfate-catalyzed free radical polymerization in water, resulting in high monomer conversion. This copolymer was then complexed with aluminum sulfate, forming an admixture containing Al(SO4)(OH)·5H2O, which was subsequently combined with silica gel. Characterization revealed that the synthesized copolymer formed a large, thin membrane that covered both the aluminum compounds and the silica gel blocks. The introduction of this complex admixture, combining the copolymer and aluminum sulfate, not only reduced the setting times of the cement paste but also enhanced the mechanical strengths of the mortar compared to using aluminum sulfate alone. The complex admixture led to the formation of katoite, metajennite, and C3A (tricalcium aluminate) in the mortar, demonstrating significant linking effects, whereas pure aluminum sulfate could not completely transform C3S within 24 h. Further addition of silica gel to the complex admixture further shortened the setting times of the paste, slightly reduced compressive strength, but improved flexural strength compared to the initial complex admixture. The silicon components appeared to fill the micropores and mesopores of the mortar, accelerating cement setting and enhancing flexural strength, while slightly decreasing compressive strength. This study contributed to the development of new cementing accelerators with improved hardening properties.

Removal of trace Na and K metal ions by resin-grafted crown ether for electronic-grade N-methyl pyrrolidone purification

The semiconductor industry’s rapid evolution necessitates ultra-high-purity N-methyl pyrrolidone (NMP) as an essential electronic-grade solvent. The development of an efficient coordination material to reduce trace metal ions, particularly Na and K metal ions, to below 1 ppb in NMP solution is a significant challenge. To address this, a novel coordination material, St-DVB-g-ACE, has been developed for the removal of Na and K metal ions from NMP. The material was synthesized by grafting 4′-aminobenzo-15-crown-5-ether onto a strong acid gel resin. The resulting St-DVB-g-ACE-3 exhibited excellent coordination performance for Na and K metal ions, with maximum Langmuir adsorption capacities reaching 20,000 μg/g and 33,333 μg/g, respectively. Of particular interest was the ability of St-DVB-g-ACE-3 to reduce all trace metal ions in industrial-grade NMP to below 1 ppb within a fixed bed column, achieving the stringent requirements for electronic-grade NMP at the G3 level. Additionally, the absorbent enhances the purity of NMP from 99.82 % to 99.84 %, indicating that the material is not dissolved and can exist stably in NMP. Its excellent recyclability and reproducibility make it highly practical for industrial use. Density functional theory (DFT) simulation, complemented by spectral analyses, revealed the interaction force and thermodynamic properties between Na and K metal ions and crown ether ring, and illustrated the interaction between anionic sulfonic group (−SO3−) and metal ions. The prepared resin-grafted crown ether adsorbents are highly effective in the thorough removal of trace metal ions from NMP solution, offering a novel and effective method for the production of electronic-grade NMP.

Structure-activity relationship, adsorption, and fenton-like catalytic oxidation capacity of iron-oxide nano-confined materials

In this study, iron-oxide was loaded into polystyrene macroporous microspheres containing sulfonate groups to prepare an environmental purification material with adsorption and Fenton-like oxidizing abilities. Iron-oxide is prone to inactivation due to reunion in the process of preparation and application, and this modification aimed to mitigate this problem. Subsequently, based on the microscopic characterization results and the effect on the treatment of methylene blue (MB) simulated wastewater, the structure-activity relationship of two key (OH− concentrations in precipitation solution and iron ion compositions in the impregnation solution) factors with the adsorption and catalytic oxidation ability of the iron-oxide nano-confined materials were explored. The results indicated that the samples both exhibited adsorption and catalytic oxidation capabilities. The removal efficiency of MB simulated wastewater can reached 95.3% after adsorption for 9 h, reaching 99.98% after catalytic oxidation for 6 h. In addition, the removal efficiency of the MB simulated wastewater exceeded 95% after 6 cycles. The concentration of OH− in precipitation solution could affect the volume of iron crystals on the carrier which affected the pore size of the sample and the adsorption capacity. It also influenced whether iron ions could be stably loaded inside the carrier, determining the conducting homogeneous or heterogeneous Fenton-like reactions and the stability of the samples. The composition of iron ions in the impregnating solution regulated the volume of the crystals and adsorption sites, which influenced the adsorption ability of the samples. In addition, the presence of Fe2+ could promote the progress of Fenton-like reactions. The identification results of the ROSs showed that •OH was the main free radical. The quenching experiment results showed that the contribution rate of •OH toward MB degradation reached 99.81%. In addition, the possible degradation pathways of MB were analyzed.

Efficient Solid-Phase Extraction of Neonicotinoid Insecticides from Environmental Water and Drink Samples Using a Postmodified Metal-Organic Framework.

Neonicotinoid insecticides (NNIs) are extensively utilized globally because of their efficient and broad-spectrum properties. However, their residues are also extensively distributed in the environment. Herein, MIL-101-SO3Na with abundant -NH- and sulfonate groups was synthesized via chloromethylation and nucleophilic substitution postmodification strategies and used to extract NNIs via solid-phase extraction. MIL-101-SO3Na was enhanced by introducing C-H···N hydrogen bonds to strengthen interaction forces and -SO3Na groups to adjust surface charge and enhance electrostatic attraction. This modification and the substantial specific surface area (998 m2·g-1) of the metal-organic framework markedly enhanced the enrichment efficiency of MIL-101. The proposed method based on MIL-101-SO3Na exhibited a minimal detection threshold (0.04-0.87 ng·L-1), an extensive linear spectrum (1-2000 ng·L-1), and notable accuracy (a variation of 3.02-11.8%) in water and drink samples. NNI concentrations between 0.25 and 24.2 ng·L-1 in fruit juice and tea samples were accurately identified using the proposed method, demonstrating its feasibility in practical applications. The postmodification of MIL-101-SO3Na is an exceptional and promising approach for the sensitive detection of ultratrace NNI levels in complex matrices.

The Coordination of Aluminum Sulfate with a Water-Soluble Block Copolymer Containing Carboxyl, Amide, Sulfonic and Anhydride Groups Providing Both Accelerating and Hardening Effects in Cement Setting

Two water-soluble block copolymers composed of acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and optionally maleic anhydride (MAH) were synthesized through ammonium persulfate-catalyzed free radical polymerization in water. The introduction of aluminum sulfate (AS) into the resulting mixtures significantly reduced the setting times of the paste and enhanced the mechanical strength of the mortar compared to both the additive-free control and experiments facilitated solely by pure AS. This improvement was primarily attributed to the inhibition of rapid Al3+ hydrolysis, which was achieved through coordination of the synthesized block copolymers, along with the formation of newly identified hydrolytic intermediates. Notably, the ternary copolymer (AA–AMPS–MAH) exhibited superior performance compared to that of the binary copolymer (AA–AMPS). In the early stages of cement setting, clusters of ettringite (AFt) were found to be immobilized over newly detected linkage phases, including unusual calcium silicate hydrate and epistilbite. In contrast to the well-documented role of polymers in retarding cement hydration, this study presents a novel approach by providing both accelerating and hardening agents for cement setting, which has significant implications for the future design of cement additives.

A Dy(III) Coordination Polymer Material as a Dual-Functional Fluorescent Sensor for the Selective Detection of Inorganic Pollutants.

A Dy(III) coordination polymer (CP), [Dy(spasds)(H2O)2]n (1) (Na2Hspasds = 5-(4-sulfophenylazo)salicylic disodium salt), has been synthesized using a hydrothermal method and characterized. 1 features a 2D layered structure, where the spasda3- anions act as pentadentate ligands, adopting carboxylate, sulfonate and phenolate groups to bridge with four Dy centers in η3-μ1: μ2, η2-μ1: μ1, and monodentate coordination modes, respectively. It possesses a unique (4,4)-connected net with a Schläfli symbol of {44·62}{4}2. The luminescence study revealed that 1 exhibited a broad fluorescent emission band at 392 nm. Moreover, the visual blue color has been confirmed by the CIE plot. 1 can serve as a dual-functional luminescent sensor toward Fe3+ and MnO4- through the luminescence quenching effect, with limits of detection (LODs) of 9.30 × 10-7 and 1.19 × 10-6 M, respectively. The LODs are relatively low in comparison with those of the reported CP-based sensors for Fe3+ and MnO4-. In addition, 1 also has high selectivity and remarkable anti-interference ability, as well as good recyclability for at least five cycles. Furthermore, the potential application of the sensor for the detection of Fe3+ and MnO4- was studied through simulated wastewater samples with different concentrations. The possible sensing mechanisms were investigated using Ultraviolet-Visible (UV-Vis) absorption spectroscopy and density functional theory (DFT) calculations. The results revealed that the luminescence turn-off effects toward Fe3+ and MnO4- were caused by competitive absorption and photoinduced electron transfer (PET), and competitive absorption and inner filter effect (IFE), respectively.