Direct Chemical Oxidation Research Articles

Selective Photocatalytic C-H Oxidation of 5-Methylcytosine in DNA.

Selective C-H activation on complex biological macromolecules is a key goal in the field of organic chemistry. It requires thermodynamically challenging chemical transformations to be delivered under mild, aqueous conditions. 5-Methylcytosine (5mC) is a fundamentally important epigenetic modification in DNA that has major implications for biology and has emerged as a vital biomarker. Selective functionalisation of 5mC would enable new chemical approaches to tag, detect and map DNA methylation to enhance the study and exploitation of this epigenetic feature. We demonstrate the first example of direct and selective chemical oxidation of 5mC to 5-formylcytosine (5fC) in DNA, employing a photocatalytic system. This transformation was used to selectively tag 5mC. We also provide proof-of-concept for deploying this chemistry for single-base resolution sequencing of 5mC and genetic bases adenine (A), cytosine (C), guanine (G), thymine (T) in DNA on a next-generation sequencing system. This work exemplifies how photocatalysis has the potential to transform the analysis of DNA.

An efficient chemiluminescent probe based on Ni-doped CsPbBr3 perovskite nanocrystals embedded in mesoporous SiO2 for sensitive assay of L–cysteine

This study presents an efficient chemiluminescence (CL) probe based on perovskite nanocrystals (NCs) for detection of L–cysteine (L–Cys). It consists of nickel–doped CsPbBr3 NCs embedded in the mesoporous SiO2 matrix as CL reagent and cerium (IV) as an oxidant in aqueous environment. The probe was designed for the highly selective determination of L–Cys based on its remarkable enhancing effect on the CL intensity. The colloidal nanocomposite of nickel–doped CsPbBr3 NCs@SiO2 with photoluminescence quantum yield of 58% was fabricated by ligand–assisted re–precipitation method and characterized by using UV–Vis absorption, FT–IR, X–ray diffraction, and transmission electron microscopy. The sensor was utilized to determine L–Cys in the linear concentration range of 20–300 nM with a detection limit of 12.8 nM. Direct chemical oxidation of Ni–doped CsPbBr3 NCs@SiO2 by Ce(IV) was the single cause of the formation of the excited-state NCs and subsequent production of CL. The developed probe provides outstanding selectivity towards L–Cys over structurally related compounds. Accurate determination of L–Cys in human serum samples was achieved without interference, and the results were confirmed by HPLC method.

Surface oxidation promotes the flotation of ilmenite: a critical review

Due to its high efficiency, ease of operation, and superior selectivity, flotation separation has emerged as a promising technique for the extraction of ilmenite from natural resources. In light of the solution chemistry of ilmenite, it is widely accepted that ferrous ions and ferrous hydroxy compounds serve as the primary active sites for collector adsorption across a broad range of slurry pH values. The commonly used collectors like sodium oleate and hydroxamic acid are capable of chemical bonding with Fe2+ to form complexes and then enhance the floatability of ilmenite. However, Fe3+ ions perform a higher affinity to both collectors rather than Fe2+, the formed stronger complexes are advantageous for enhancing the hydrophobicity of ilmenite and increasing the probability for air bubble attachment, resulting in an improved ilmenite flotation recovery. Consequently, how to maximize the conversion efficiency of Fe2+ to Fe3+ and provide additional Fe3+ active sites on ilmenite surface for collector attachment have become the hot spot. Herein, this review aims to firstly analyze the crystal structure and solution chemistry of ilmenite and then provide a concise summary of recent advances in different oxidation technologies for promoting the conversion of Fe2+ to Fe3+, including hydroxyl radicals oxidation, direct chemical oxidation, and thermal oxidation, and the in-depth activation mechanisms are well illustrated. Also, current challenges and perspectives in this field are discussed. This review would benefit the development of next-generation flotation techniques for earth-abundant titanium resources.

P-Arsanilic acid decontamination over a wide pH range using biochar-supported manganese ferrite material as an effective persulfate catalyst: Performances and mechanisms

Direct chemical oxidation and pure adsorption could not effectively remove p-Arsanilic acid (p-ASA) and the released inorganic arsenic. Herein, one novel biochar supported MnFe2O4 (MFB) was synthesized and adopted for p-ASA degradation and synchronous adsorption of the generated inorganic arsenic. The MFB/persulfate (PS) system could remain effective under a wide pH range (3.0–9.0), and the released arsenic could be removed simultaneously by MFB. Mechanism investigation revealed that the functional groups of MFB (i.e. O–C=O and C=O), Fe and Mn oxides on MFB all contributed to PS activation. O2·− and 1O2 were the main reactive oxygen species (ROS) responsible for p-ASA degradation, and 1O2 was the predominant ROS. Besides, the MFB possessed superior reusability. Therefore, it is expected to develop a potential method for organic arsenic contaminants removal via an oxidation-adsorption process, and the results could also shed light on the better understanding of the PS activation mechanisms.Graphical

The chemiluminescence of AgInS2 quantum dots and its application as a sensing platform for glutathione assay

Herein, we prepared highly luminescent water-soluble AgInS2 quantum dots (AIS QDs) by a green and simple hydrothermal method and characterized them by various spectroscopic and microscopic techniques. The chemiluminescence (CL) of AIS QDs induced by direct chemical oxidation was investigated. It was found that NaIO4 in alkaline solution elicits a remarkable CL from these QDs. The CL was proved to be originated from the excited-state QDs, produced during the reaction. Further studies revealed that the addition of glutathione (GSH) to NaIO4-AIS QDs system effectively increased the CL intensity. This was employed as a sensing platform for sensitive assay of GSH. In the optimized conditions, the relation between the CL intensity and GSH concentration was linear in the range of 1.0 × 10−9 mol L−1 to 5.0 × 10−6 mol L−1 with a detection limit of 2.8 × 10−10 mol L−1. To evaluate the practical usefulness of the assay, the established technique was applied to the analysis of human plasma.

Synthesis of MWCNT/PPY nanocomposite using oxidation polymerization method and its employment in sensing such as CO2 and humidity

This paper includes the synthesis of a composite of multiwall carbon nanotube (MWCNT) and conducting polymer polypyrrol (PPY) and its characterizations along with the applications direct liquid injection chemical vapour deposition (DLICVD) and oxidation polymerization method have been used for the synthesis of MWCNT and MWCNT/PPY nanocomposite respectively. MWCNT/PPY's thin film was prepared using the technique of spin coating and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), particle size analyzer and X-ray diffractometer (XRD). Raman spectroscopy has been used to observe the vibrational and rotational spectra of MWCNT and MWCNT/PPY nanocomposite. The optical bandgap and minimum crystallite size have been calculated and found to be 3.2 eV and 8.1 nm respectively. The synthesized MWCNT/PPY has been used for CO2 and humidity sensing at room temperature (300 K). The sensor response of thin-film towards CO2 was found to be 7.2 at 1000 ppm and minimum response and recovery time at 250 ppm were found to be 30 s and 37 s respectively. The sensitivity of thin-film towards humidity was found to be 41.33 kΩ/%RH. The theoretical calculation was also performed in support of experimental data.

Facile and Scalable Modification of a Cu Current Collector toward Uniform Li Deposition of the Li Metal Anode.

The development of lithium metal anodes has been severely impeded by the detrimental lithium (Li) dendrite growth which can largely shorten the lifespan of the battery. Here, we propose a one-step redox strategy to fabricate reduced graphene oxide (rGO) and Cu2O co-modified Cu current collector (rGO-Cu2O/Cu), which can guide the uniform Li ion nucleation and suppress the formation of the Li dendrite. The lithiophilic Cu2O in situ grown on the Cu substrate via direct chemical oxidation of Cu foil by the GO solution can decrease the Li nucleation overpotential and regulate the preferential nucleation of Li ions, while the rGO produced at the same time can facilitate the electron transport. As the consequence of the synergistic effects, rGO-Cu2O/Cu could be fully discharged with largely enhanced Coulombic efficiency of 98% and extended cycling life of the symmetrical cell up to 300 h. The full battery assembled with LiFePO4 also exhibits satisfying electrochemical performance, indicating the promising practical application of this Li-plated rGO-Cu2O/Cu anode. Furthermore, the processable rGO-Cu2O/Cu which can make Li metal anode moldable into various shapes with a controllable size will be favorable to manufacture diverse device architectures.

A Reversible Electron Relay to Exclude Sacrificial Electron Donors in the Photocatalytic Oxygen Atom Transfer Reaction with O2 in Water

AbstractUsing light energy and O2 for the direct chemical oxidation of organic substrates is a major challenge. A limitation is the use of sacrificial electron donors to activate O2 by reductive quenching of the photosensitizer, generating undesirable side products. A reversible electron acceptor, methyl viologen, can act as electron shuttle to oxidatively quench the photosensitizer, [Ru(bpy)3]2+, generating the highly oxidized chromophore and the powerful reductant methyl‐viologen radical MV+.. MV+. can then reduce an iron(III) catalyst to the iron(II) form and concomitantly O2 to O2.− in an aqueous medium to generate an active iron(III)‐(hydro)peroxo species. The oxidized photosensitizer is reset to its ground state by oxidizing an alkene substrate to an alkenyl radical cation. Closing the loop, the reaction of the iron reactive intermediate with the substrate or its radical cation leads to the formation of two oxygenated compounds, the diol and the aldehyde following two different pathways.

A Reversible Electron Relay to Exclude Sacrificial Electron Donors in the Photocatalytic Oxygen Atom Transfer Reaction with O2 in Water.

Using light energy and O2 for the direct chemical oxidation of organic substrates is a major challenge. A limitation is the use of sacrificial electron donors to activate O2 by reductive quenching of the photosensitizer, generating undesirable side products. A reversible electron acceptor, methyl viologen, can act as electron shuttle to oxidatively quench the photosensitizer, [Ru(bpy)3 ]2+ , generating the highly oxidized chromophore and the powerful reductant methyl-viologen radical MV+. . MV+. can then reduce an iron(III) catalyst to the iron(II) form and concomitantly O2 to O2.- in an aqueous medium to generate an active iron(III)-(hydro)peroxo species. The oxidized photosensitizer is reset to its ground state by oxidizing an alkene substrate to an alkenyl radical cation. Closing the loop, the reaction of the iron reactive intermediate with the substrate or its radical cation leads to the formation of two oxygenated compounds, the diol and the aldehyde following two different pathways.

Oxidative Degradation of Tannic Acid in Aqueous Solution by UV/S2O82− and UV/H2O2/Fe2+ Processes: A Comparative Study

Tannic acid (TA) is a major pollutant present in the wastewater generated from vegetable tanneries process and food processing. This work studied TA degradation by two advanced oxidation processes (APOs): UV irradiation at the wavelength of 254 nm in the presence of hydrogen peroxide (H2O2) and ferrous iron (photo-Fenton) and in the presence of potassium persulfate. The influence of certain experimental parameters such as K2S2O8, H2O2, Fe2+, and TA concentrations, initial pH and temperature was evaluated in order to obtain the highest efficiency in terms of aromatics (decay in UV absorbance at 276 nm) and TOC removals. Chemical oxidation of TA (0.1 mM) by UV/persulfate achieved 96.32% of aromatics removal and 54.41% of TOC removal under optimized conditions of pH = 9 and 53.10 mM of K2S2O8 after 60 min. The treatment of TA by photo-Fenton process successfully led to almost complete aromatics removal (99.32%) and high TOC removal (94.27%) from aqueous solutions containing 0.1 mM of TA at natural pH = 3 using 29.4 mM of H2O2 and 0.18 mM of Fe2+ at 25 °C after 120 min. More efficient degradation of TA by photo-Fenton process than UV/persulfate was obtained, which confirms that hydroxyl radicals are more powerful oxidants than sulfate radicals. The complete removal of organic pollution from natural waters can be accomplished by direct chemical oxidation via hydroxyl radicals generated from photocatalytic decomposition of H2O2.

Chemiluminescence of CsPbBr3 Perovskite Nanocrystal on the Hexane/Water Interface.

All-inorganic halide perovskite CsPbBr3 nanocrystals (NCs) have attracted more attention in recent years due to the unique optical feature. To date, most of the research was mainly focused on the photoluminescence (PL) and electrochemiluminescence (ECL) of the perovskite NCs. In this work, the strong chemiluminescence (CL) emission of CsPbBr3 NCs was observed for the first time on the hexane/water interface with the assistance of ammonium persulfate-(NH4)2S2O8 as coreactant. Different coreactants were investigated to demonstrate the effect on the CL behavior and it was found that CL intensity achieved the maximum in the presence of (NH4)2S2O8. In this system, electron transfer took place on the surface of the CsPbBr3 NCs, and the excited CsPbBr3 NCs was originated from the direct chemical oxidation of (NH4)2S2O8. The CL spectrum of CsPbBr3 NCs was also collected and was consistent with their PL and ECL spectra, indicating that CsPbBr3 NCs played a role of luminophor during the CL process. The discovery of monochromatic CL of highly crystallized CsPbBr3 NCs not only extends the applications of halide perovskite materials in the analytical field but also provides a new route for the exploration of the physical chemistry properties.

Constraints of bioleaching in in-situ recovery applications

The potential role of microorganisms in the in-situ recovery (ISR) of technology metals, in particular from reduced ores through acidic leaching is not well understood, but attracts increasing interest worldwide. Based on electron balance criteria, upper limits for metal recovery in general and bioleaching effects in particular are deduced in this work. These criteria define restrictions valid for any metal (U, Cu, Zn, etc.), oxidant (ferric iron, O2), and type of leaching (pure chemical leaching and/or bioleaching). The indirect catalysis of leaching by microbial (re-)oxidation of Fe+2 to Fe+3 is a well-verified mechanism; however, for practical applications it is constrained by the in-situ availability of O2. The content of O2 in the injected leachant is limited by its low solubility as a function of temperature and pressure. The ex-situ bio-oxidation of Fe in an aerated bioreactor is considered as an alternative to the direct (and fast) chemical oxidation, e.g. by the more economic H2O2 injection into the leachant pipeline. Reactive transport modeling of in-situ leaching of sulfidic Cu ores demonstrates the role of key parameters for (bio)leaching productivity: pH, amount of oxidants, flow rate, and porosity. In reality, sulfides dissolve kinetically, as demonstrated. A pure thermodynamic approach, however, already provides a theoretical upper limit of both the (predominant) direct chemical leaching by Fe+3 and the possible effect of (indirect) bioleaching by re-oxidizing Fe+2 that is constrained by in-situ O2.

Development of Kinetic Models for the Long-Term Corrosion Behavior of Candidate Alloys for the Canadian SCWR

Corrosion behavior of Inconel 625 and Incoloy 800H, two of the candidate fuel cladding materials for Canadian supercritical water-cooled reactor (SCWR) designs, was evaluated by exposing the metals to supercritical water (SCW) in the University of New Brunswick’s flow loop. A series of experiments were conducted over a range of temperatures between 370 °C and 600 °C, and the corrosion rates were evaluated as the weight change of the materials over the exposure time (typical experiments measured the weight change at intervals of 100, 250, and 500 h, with some longer-term exposures included). Scanning electron microscopy (SEM) was used to examine and quantify the oxide films formed during exposure and the corrosion mechanisms occurring on the candidate metals. Data from in-house experiments were used to create an empirical kinetic equation for each material that was then compared to literature values of weight change. Dissolved oxygen concentrations varied between experimental sets, but for simplicity were ignored since the effect of dissolved oxygen has been demonstrated to be a minor secondary effect. Activation energies for the alloys were determined with Inconel 625 and Incoloy 800 H showing a distinct difference between the low-temperature electrochemical corrosion (EC) mechanism and direct high-temperature chemical oxidation (CO). The results were modeled using these separate effects showing dependence on the bulk density and dielectric constant of the supercritical water through the hydrogen ion concentration.

Microfluidic photoinduced chemical oxidation for Ru(bpy)33 + chemiluminescence — A comprehensive experimental comparison with on-chip direct chemical oxidation

For the first time, the analytical figures of merit in detection capabilities of the very less explored photoinduced chemical oxidation method for Ru(bpy)32+ CL has been investigated in detail using 32 structurally different analytes. It was carried out on-chip using peroxydisulphate and visible light and compared with well-known direct chemical oxidation approaches using Ce(IV). The analytes belong to various chemical classes such as tertiary amine, secondary amine, sulphonamide, betalactam, thiol and benzothiadiazine. Influence of detection environment on CL emission with respect to method of oxidation was evaluated by changing the buffers and pH. The photoinduced chemical oxidation exhibited more universal nature for Ru(bpy)32+ CL in detection towards selected analytes. No additional enhancers, reagents, or modification in instrumental configuration were required. Wide detectability and enhanced emission has been observed for analytes from all the chemical classes when photoinduced chemical oxidation was employed. Some of these analytes are reported for the first time under photoinduced chemical oxidation like compounds from sulphonamide, betalactam, thiol and benzothiadiazine class. On the other hand, many of the selected analytes including tertiary and secondary amines such as cetirizine, azithromycin fexofenadine and proline did not produced any analytically useful CL signal (S/N=3 or above for 1μgmL−1 analyte) under chemical oxidation. The most fascinating observations was in the detection limits; for example ofloxacin was 15 times more intense with a detection limit of 5.81×10−10M compared to most lowest ever reported 6×10−9M. Earlier, penicillamine was detected at 0.1μgmL−1 after derivatization using photoinduced chemical oxidation, but in this study, we improved it to 5.82ngmL−1 without any prior derivatization. The detection limits of many other analytes were also found to be improved by several orders of magnitude under photoinduced chemical oxidation.

Dissolution of NaTi2(PO4)3 in Alkaline Solutions and Its Implications for Use As an Aqueous Anode

There are two primary qualities batteries used for grid-scale storage should have (1) a low levelized cost of energy storage (LCOE) or a low $/kWh delivered over the lifetime of the battery and (2) a high degree of safety which includes low toxicity, low flammability, and low corrosiveness. Aqueous rechargeable alkali-ion batteries offer a promising alternative to Li-ion batteries for grid-scale electrochemical energy storage installations because of their lower cost of and higher safety. However, with the exception of systems that utilize activated carbon based anodes, demonstrated chemistries show significant capacity fade. Although a decent amount of research has been done on failure mechanism of intercalation cathodes in aqueous solution, few studies have been carried out to elucidate the role of the anode material in battery failure. Sodium super ionic conductor (NASICON) type NaTi2(PO4)3 is one of the most promising materials for aqueous anodes. It has good chemical stability, a high theoretical specific capacity of 133 mAh/g, low cost of manufacture, and a favorable redox potential. However, it is often reported to be cycled in neutral aqueous solution, which when given its low redox potential implies there will be some amount of water decomposition occurring. Water decomposition occurs due to both direct electrochemical hydrogen evolution, as well as direct chemical oxidation of the fully sodiated NaTi2(PO4)3. In this work we have set out to quantify the inherent chemical stability of NaTi2(PO4)3 in alkaline solutions using inductively coupled mass spectrometry (ICP-MS), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), cyclic voltammeter (CV), and in-situ pH measurements. It was found that at pH > 11 dissolution begins to occur but does not become significant until pH > 12.7. At the highest tested pH an unidentified phase with an elongated morphology becomes thermodynamically favorable and begins to precipitate from solution. This secondary phase acts as a sink for dissolved titanium allowing for the continual dissolution of NaTi2(PO4)3 rather then eventual saturation of solvated titanium species. The in-situ pH measurement indicates that upon cycling in neutral solution the electrode undergoes a pH swing from lower pH to higher pH due to the generation of OH- ions, followed by their diffusion out of the electrode. This increase followed by decrease in pH exacerbates the dissolution of NaTi2(PO4)3 and leads to a continual dissolution precipitation reaction. The combination of FTIR and XRD indicate that these precipitated phases were a mixture of layered titantes of the form NaxH2-xTinO2n+1-yH2O. Although NaTi2(PO4)3 appears to be susceptible to dissolution at higher pH, the measured dissolution does not account for the overall capacity fade seen upon cycling. The authors are currently investigating the effect of gas generation and entrapment on the loss of electrochemical surface area and its effect on the apparent capacity fade.

Enhanced chemiluminescence from reactions between CdTe/CdS/ZnS quantum dots and periodate

A novel chemiluminescence (CL) performance of CdTe/CdS/ZnS quantum dots (QDs) with periodate (KIO4) was studied. Effects of concentration and pH on the CL system were investigated. Electron spin resonance (ESR) and the effects of radical scavenger analysis were employed for identification of intermediate species. The CL spectra for this system showed only one maximum emission peak centered around 620nm, which was similar with photoluminescence (PL) spectra of CdTe/CdS/ZnS QDs. The CL of CdTe/CdS/ZnS QDs was induced by direct chemical oxidation and the possible mechanism could be explained by radiative recombination of injected holes and electrons. This investigation not only provided new sight into the optical characteristics of CdTe/CdS/ZnS QDs, but also broadened their potential optical utilizations.

Chemiluminescence of graphene quantum dots and its application to the determination of uric acid

We report on the chemiluminescence (CL) of graphene quantum dots (GQDs) induced by direct chemical oxidation. GQDs were prepared by a simple carbonization method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and Raman spectroscopy. It was found that Ce(IV) could oxidize GQDs to produce a relatively intense CL emission. The mechanism of CL generation was investigated based on the fluorescence and CL emission spectra. It was attributed to the radiative recombination of oxidant-injected holes and thermally excited electrons in the GQDs. In order to show the analytical application potential of GQDs-Ce(IV) CL system, it was applied to the determination of uric acid. Under the optimized conditions, the proposed CL system exhibited excellent analytical performance for determination of uric acid in the range of 1.0×10−6M–5.0×10−4M with a limit of detection of 5.0×10−7M. The method was applied to the determination of uric acid in human plasma and urine samples, with satisfactory results.

Gas phase recovery of hydrogen sulfide contaminated polymer electrolyte membrane fuel cells

The effect of hydrogen sulfide (H2S) on the anode of a polymer electrolyte membrane fuel cell (PEMFC) and the gas phase recovery of the contaminated PEMFC using ozone (O3) were studied. Experiments were performed on fuel cell electrodes both in an aqueous electrolyte and within an operating fuel cell. The ex-situ analyses of a fresh electrode; a H2S contaminated electrode (23 μmolH2S cm−2); and the contaminated electrode cleaned with O3 shows that all sulfide can be removed within 900 s at room temperature. Online gas analysis of the recovery process confirms the recovery time required as around 720 s. Similarly, performance studies of an H2S contaminated PEMFC shows that complete rejuvenation occurs following 600-900 s O3 treatment at room temperature. The cleaning process involves both electrochemical oxidation (facilitated by the high equilibrium potential of the O3 reduction process) and direct chemical oxidation of the contaminant. The O3 cleaning process is more efficient than the external polarization of the single cell at 1.6 V. Application of O3 at room temperature limits the amount of carbon corrosion.Room temperature O3 treatment of poisoned fuel cell stacks may offer an efficient and quick remediation method to recover otherwise inoperable systems.

Direct chemiluminescence of carbon dots induced by potassium ferricyanide and its analytical application

The chemiluminescence (CL) of water-soluble fluorescent carbon dots (C-dots) induced by direct chemical oxidation was investigated. C-dots were prepared by solvothermal method and characterized by fluorescence spectra and transmission electron microscopy. It was found that K3Fe(CN)6 could directly oxidize C-dots to produce a relatively intense CL emission. The mechanism of CL generation was investigated based on the fluorescence and CL emission spectra and the effect of radical scavengers on the CL intensity. The inhibitive effect of some metal ions and biologically important molecules on the CL intensity of the system was examined and the potential of the system for the determination of these species at trace levels was studied. In order to evaluate the capability of method to real sample analysis, it was applied to the determination of Cr(VI) and adrenaline in water and injection samples, respectively.

Chemiluminescence of Mn-Doped ZnS Nanocrystals Induced by Direct Chemical Oxidation and Ionic Liquid-Sensitized Effect as an Efficient and Green Catalyst

A novel chemiluminescence (CL) method was proposed for doping water-soluble Mn in ZnS quantum dots (QDs) as CL emitter. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solution. These nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy, and photoluminescence (PL) emission spectroscopy. The CL of ZnS QDs was induced directly by chemical oxidation and its ionic liquid-sensitized effect in aqueous solution was then investigated. It was found that oxidants, especially hydrogen peroxide, could directly oxidize ZnS QDs to produce weak CL emission in basic solutions. In the presence of 1,3-dipropylimidazolium bromide/copper, a drastic light emission enhancement was observed which is related to a strong interaction between Cu2+and the imidazolium ring. In these conditions, an efficient CL light was produced at low pH which is suggested to be beneficial to the biological analysis. The CL properties of QDs not only will be helpful to study physical chemistry properties of semiconductor nanocrystals but also they are expected to find use in many fields such as luminescence devices, bioanalysis, and multicolor labeling probes.