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Removing heavy metals from aqueous solutions has drawn more and more attentions these years because of their serious global health challenge to human society. To develop an adsorbent with low-cost and high-efficiency for removal of heavy metals (HMs), β-cyclodextrin (β-CD) polymers crosslinked with rigid aromatic groups were prepared and used for lead (Pb), copper (Cu) and cadmium (Cd) removal for the first time. The negatively charged β-CD polymers with large BET surface area were suitable to be used in HMs adsorption. The adsorption process completed in 5 min was well fit by Freundlich isotherm model and pseudo-second-order model. The intraparticle diffusion model was also appropriate to describe the adsorption of Pb, Cu and Cd on β-CD polymer. The maximum of adsorption capacities at 25 °C for Pb, Cu and Cd were 196.42, 164.43 and 136.43 mg/g when the initial concentration was 200 mg/L. The HMs adsorption process on the surface of β-CD polymer was an endothermic and spontaneous process. Both of the electrostatic interaction and distribution of Pb, Cu and Cd species influenced the adsorption process at different pH values. The order of removal efficiencies in multi-component adsorption for the three metal ions were Pb > Cu > Cd. The adsorption mechanisms were H + ions on hydroxyl groups exchanged with heavy metal ions and electrostatic interactions. This study indicated that β-CD polymers could be developed into effective adsorbents for rapid removal of heavy metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • SERS detection of SCC by intermolecular high-affinity. • CTAB has high molecular affinity with the quaternary ammonium salt structure of SCC. • Au NRs substrates with uniform hot spots were prepared by self-assembly method. • Realize the rapid and sensitive detection of SCC at the level of 2 × 10-8 M in plasma. Succinylcholine chloride (SCC) is a common poison that threatens human life. At present, there is a lack of research on its on-site rapid detection methods. In this work, the use of gold nanorods as an enhanced substrate based on the high affinity between the quaternary ammonium salt structure can achieve rapid SERS detection of SCC in plasma. The long alkane chain structure of cetyltrimethylammonium bromide (CTAB) and the quaternary ammonium salt structure of SCC have a high molecular affinity, so that the target molecule can show a strong and obvious characteristic signal of SERS. Combined with a simple pretreatment method, acetonitrile is used as a protein precipitation agent to effectively remove matrix interference. The constructed SERS substrate can achieve the sensitive detection of 2 × 10-8 M level of SCC in plasma samples and has high detection reproducibility. The entire pre-processing and testing process can be completed within 7 min, which can be used as an important technical basis for the preliminary identification of on-site SCC-related drug cases. The research results provide an effective solution for the establishment of SCC analysis strategies in complex matrices, and can provide new ideas for solving the problems of difficult identification of common poisons in the field and the lack of rapid detection methods on site. [ABSTRACT FROM AUTHOR]

Surface-enhanced resonance Raman scattering (SERRS) is not realized for most molecules of interest. Here, we developed a new SERRS platform for the fast and sensitive detection of 2,4,6-trinitrotoluene (TNT), a molecule with low Raman cross section. A cationic surfactant, cetylpyridinium chloride (CPC) was modified on the surface of silver sols (CP-capped Ag). CPC not only acts as the surface-seeking species to trap sulfite-sulfonated TNT, but also undergoes complexation with it, resulting in the presence of two charge-transfer bands at 467 and 530 nm, respectively. This chromophore absorbs the visible light that matches with the incident laser and plasmon resonance of Ag sols by the use of a 532.06 nm laser, and offered large resonance Raman enhancement. This SERRS platform evidenced a fast and accurate detection of TNT with a detection limit of 5×10−11 M under a low laser power (200 μW) and a short integration time (3 s). The CP-capped Ag also provides remarkable sensitivity and reliable repeatability. This study provides a facile and reliable method for TNT detection and a viable idea for the SERS detection of various non-resonant molecules. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a one-step synthesis and controlled assembly of Au nanoparticles (NPs) on λ-DNA scaffolds by an in-situ photoreduction method. The interparticle gaps of the Au NPs attached on DNA can be fine regulated by controlling the R values (denoted as the ratio of Au(III) ions added per DNA base pair). At R = 20, the interparticle gap between two adjacent Au NPs on DNA is in the range of 1–3 nm para-aminothiophenol (PATP) as a Raman reporter is used to evaluate the surface-enhanced Raman scattering (SERS) performance of these DNA–Au hybrid substrates. Empirical enhancement factor above 1 × 109 is observed when the R value is in a fairly broad range of 10–60 under 785 nm excitation. At R = 20, this DNA–Au hybrid as SERS substrate can give a low detection limit of 0.5 nM of PATP, moreover, these substrates have a good reproducibility at different sites on a substrate, with a standard deviation of <15%. These results indicate that the photoreduced Au NPs on DNA scaffolds can be used as SERS-active substrates which exhibit high and reproducible SERS activity. This DNA–Au hybrid has potential applications in chemical and biological SERS analysis. Furthermore, the synthesis process is so simple and quick, which needs just only 15 min. Combined with the ability to make preformed scaffolds, the selective deposition of Au NPs on fixed DNA scaffolds will be an important addition to the rapidly growing nanofabrication tool kit for in-field SERS detection. [Copyright &y& Elsevier]

Abstract: This study found that 1,2-ethylenediamine (EDA) as a primary amine could be modified onto the surface of citrate-stabilized gold nanoparticles (Au NPs), and the EDA-capped Au NPs were successfully used as an ultrasensitive optical probe for TNT detection. The strong donor–acceptor (D–A) interactions between EDA and trinitrotoluene (TNT) at the Au NP/solution interface induced significant aggregation of the EDA-capped Au NPs, and enabled to easily realize the direct colorimetric detection of ultratrace TNT. The results showed that such a color change was readily seen by the naked eye, and the colorimetric detection could be down to 400pM level of TNT with excellent discrimination against other nitro compounds. UV–vis absorption spectroscopy was used to examine the TNT-induced changes in local surface plasmon resonance (LSPR) of EDA-capped Au NPs, and a new LSPR band at ca. 630nm arose along with the addition of TNT, which produced a detection limit of TNT down to ca. 40pM. Furthermore, dynamic light scattering measurements evidenced the ultratrace TNT-induced small changes in the size of the EDA-capped Au NPs, and realized the quick and accurate detection of TNT in 0.4pM level. These results demonstrated the ultrahigh sensitivity of this optical probe for TNT detection. Moreover, this optical probe is sample, stable, low-cost, and these excellent properties make it quite promising for infield and rapid detection of TNT. [Copyright &y& Elsevier]

Trinitrotoluene (TNT) is a primary component in chemical explosives, making them a common focus in public safety detection. However, it is very difficult to achieve selective and sensitive detection of the TNT molecule in practical application. In the present study, a simple surface enhanced Raman scattering (SERS) sensing based on monoethanolamine (MEA) - modified gold nanoparticles (Au NPs) was expanded for high selectivity and sensitive detecting of TNT in an envelope, luggage, lake water, and clothing through a quickly sampling and detection process. The monoethanolamine molecule based on Meisenheimer complex lights up ultra-high Raman scattering of a nonresonant molecule on the superficial coat of gold nanoparticles. Using this detection sensor, a molecular bridge can be established to selectively detect trinitrotoluene with a detection limit of 21.47 pM. We were able to rapidly identification trinitrotoluene molecule with a powerful selective over the familiar interfering substances nitrophenol, picric acid, 2,4-dinitrophenol, and 2,4-dinitrotoluene. The outcome in this work supply an efficient solution to the test of trinitrotoluene and to establishing a SERS sensor analytical strategy. The studies have demonstrated that the MEA-Au NPs based SERS sensing can be potentially used in field detection the trace amount of chemical explosives for public security. Image 1 • MEA can be rapid modified onto the surface of citrate-stabilized Au NPs. • The sensor has an excellent discrimination against other nitro compounds. • TNT forms a red-colored Meisenheimer complex with MEA in solution phase. • MEA modified Au NPs can be used as an ultrasensitive SERS sensor for TNT detection. • SERS assays for TNT can be down to 21.47 pM level. [ABSTRACT FROM AUTHOR]

A rapid and accurate method for the sensitive detection of illegal drug additives including atenolol (ATN), metformin hydrochloride (MET), and phenformin hydrochloride (PHE) in health products using solvent microextraction (SME) combined with surface-enhanced Raman spectroscopy (SERS) was developed. Various illegal drug additives in different health products were separated via microextraction and then detected in situ using a portable Raman spectrometer with Ag colloids acting as SERS-active substrates. The effects of experimental parameters on the detection sensitivity and producibility were evaluated, and the applications of illegal additives spiked into samples were systematically investigated with SME-SERS. It was demonstrated that the mixture of CH3OH and CHCl3 (v/v = 1 : 4) as the extractant was suitable for the rapid microextraction separation of illegal drug additives and also induced the distribution of the Ag colloids (2 M) on the CHCl3 surface. More importantly, CH3OH can carry the drug molecules to enter into the inter-particles of the Ag colloids in this process, and then significantly improve the detection sensitivity of illegal drug additives. Furthermore, the high-throughput and real-time detection of illegal drug additives spiked into health products with SME-SERS in multi-well 96 plates were achieved with the level of 0.1 μg mg−1. The results reveal that this rapid and convenient method could be used for the effective separation and sensitive detection of illegal additives in complex specimen. [ABSTRACT FROM AUTHOR]

The development of sensitive and rapid methods for analysis and detection of small molecules is highly desirable for medical diagnostics and therapeutics. We report an acupuncture needle functionalized with gold nanoparticles (Au NPs) and a macrocyclic amine (MA) Raman tag as the platform to realize the sensitive detection of adenosine triphosphate (ATP) by surface-enhanced Raman spectroscopy (SERS). The assembled Au NPs with abundant hot spots on the surface of the needle avoids the aggregation of Au NPs and results in a good signal response. Moreover, there is strong combination between ATP and MA through electrostatic adsorption, hydrogen-bonding interactions, and π–π stacking, and as a consequence, this functionalized needle can be used as a SERS platform for detection of ATP (25 nM) through a decrease of the Raman signal of MA resulting from the high chemical affinity of ATP for MA. Specially, the Au NP/MA-functionalized needle is conveniently used to monitor ATP (100 nM) added to serum, and demonstrates great promise in the study and detection of ATP in a complex sample, laying the foundation for SERS applications in complex acupuncture specimens with fast response and simple operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Long-time stable hot spots is obtained by controlling the evaporation rate of sol with changing of temperature. • An automatic focusing method based on spectral intensity was proposed to capture the best hot spot. • The optimized hill climbing effectively avoids falling into the local optimal solution in the process of auto focusing. In the manual dynamic surface-enhanced Raman spectroscopy (D-SERS) detection process, it is difficult to focus on sample drop due to the constantly changing hotspot and easy judgment method. In this paper, we proposed an automatic focusing method based on long time stable hotspot with aid of optimization of hill-climbing algorithm and achieved on a designed device. First, set up a high temperature accelerating evaporation process to obtain hotspot and then cool to a low temperature rapidly to maintain it. Then, the spectral intensity was used as a focus of feedback signal in optimized hill-climbing algorithm to drive the sample stage to move up and down to adjust the depth of the laser on the samples to realize automatic focusing. As a result, the hotspot can be maintained for 5 min, and the autofocusing result can be achieved within 9 s, while the sensitivity was improved with two orders of magnitude in D-SERS detection of crystal violet (CV) compared with manual focusing. [ABSTRACT FROM AUTHOR]

Abstract Retinal ganglion cells (RGCs) apoptosis and their axon degeneration are pivotal features in glaucoma. Previous studies suggest that the process of RGCs soma degeneration is distinct from axon degeneration and that both of them lead to vision loss but separately. However, since a normal visual function relies on the integrity of axon, synapse and soma in the retina, a comprehensive understanding of the changes of these neuron components in glaucoma is desired. Therefore, in an acute ocular hypertension (AOH) model in mice, we systematically evaluated retinal neuron soma, axon and synapse alteration at certain time points. We found that ocular hypertension led to a progressive apoptosis of retinal neural cells which proceeded from peripheral to central retina in the wholemount, meanwhile, started in the ganglion cell layer (GCL) and spread to the inner nuclear layer (INL) and then the outer nuclear layer (ONL) as time went on. The type of apoptotic cells was identified as RGCs in GCL, amacrine cells in INL and cone photoreceptor cells in ONL. Axon degeneration was observed at the same time as soma degenerated and also progressed from peripheral to central retina. More interestingly, accumulation of neurofilament in the soma caused by axon transport failure was detected synchronously. We also found that presynaptic and postsynaptic vesicle proteins were downregulated. Taken together, these data support a view that retinal neuronal apoptosis happens not only in RGCs, but also other neurons in laminar layers. Axon damage and synapse loss occur synchronously with soma loss in AOH. The combination of these three parameters might facilitate a systematic evaluation of the disease progression and treatment strategies in glaucoma. Highlights • Acute ocular hypertension results in retinal neural apoptosis spreading from GCL to INL and ONL, where RGCs, amacrine cells and cone photoreceptor cells were all affected. • Axon degeneration and somatic neurofilament accumulation progressing from peripheral to central retina was detected as the same time as soma loss. • Synaptic defects occur simultaneously. [ABSTRACT FROM AUTHOR]

Difficult, but excellent surface‐enhanced resonance Raman scattering (SERRS) provides a fast and accurate method for the detection of ultra‐small traces of trinitrotoluene (TNT) under low laser power and in a short integration time. In their Full Paper on page 8789 ff., H. L. Liu, L. B. Yang, J. H. Liu et al. describe how cetylpyridinium chloride modified on Ag sols not only acts as the surface‐seeking species to trap sulfite‐sulfonated TNT, but also undergoes complexation with the sulfonated TNT, resulting in the appearance of two charge‐transfer bands at 467 and 530 nm. [ABSTRACT FROM AUTHOR]

To improve the sensitivity of surface‐enhanced Raman spectroscopy (SERS) by constructing smaller hot spots and making the target molecules more accessible, a liquid–liquid interface assembly method is used to construct a three‐layer Ag nanoparticle film structure, wherein the nanoparticles between the adjacent upper and lower layers form natural smaller gaps of 1–3 nm. The target solution is pumped into these gaps using the principle of natural transpiration (the nanopump effect). The resulting hot spot density and efficiency are significantly higher than that of the normal dry‐state method. In addition, the detection limit reaches 1 amol, which is a reduction of 2–3 orders of magnitude compared to the dry‐state method. It is also demonstrated that this dynamic detection process is suitable for detecting the substance changes occurring during sperm–oocyte binding. This method therefore provides a new means for target molecules to actively enter naturally interbedded smaller gaps and provides essentially unlimited possibilities for SERS detection. [ABSTRACT FROM AUTHOR]

The aggregation of nanoparticles is the key factor to form hot spots for the flocculation-enhanced Raman spectroscopy (FLERS) method. However, the structure of flocculation is still not clear. It is therefore necessary to explore and analyze the aggregation process of nanoparticles more carefully, so as to realize a better application of FLERS. Here, we report the application of in situ liquid cell transmission electron microscopy (TEM) combined with an in situ high-speed camera to analyze the particle behaviors. The results showed that flocculation can exist stably and the gap between the nanoparticles in the flocculation always remained at 7–9 nm, which ensured the high stability and sensitivity of the FLERS method. We successfully applied FLERS to the in situ noninvasive probing of cupping effect substances. The results indicated the scientific principle behind the traditional Chinese medicine method to some extent, which thus provides a new and effective method for the in situ dynamic monitoring of biological systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pretreatment of target poisons in oily substrates was achieved by ethanol extraction. • Highly sensitive detection of paraquat and diquat at ppb level is realized. • The optimal SERS substrates were prepared to match the handheld Raman spectrometer. • The reliability of the proposed method was verified by a double-blind experiment. The sensitive detection and identification of toxicants in oily matrices have suffered from difficulty in poisoning incidents, therefore it is necessary to develop the rapid and efficient analytical method to realize the on-site screening and analyzing. In this report, the surface-enhanced Raman spectroscopy (SERS) method was used to detect paraquat and diquat poisons in various oily matrix coupled with solvent extraction. The solvent extraction not only remove interfering impurities of oily substrates, but also can enrich and separate the poisons from oily matrix. It was demonstrated that the ethanol as the extractant was suitable for the rapid separation of poisons such as paraquat (PQ) and diquat (DQ) in oily matrix (soy sauce, pasta sauce, sesame oil, chili oil). Moreover, combined with a handheld Raman spectrometer, the entire detection process was completed within 8 min with the level of 10 ppb PQ and 100 ppb DQ. Furthermore, double-blind experiments verify the reliability of this method. The results demonstrate that this rapid and convenient method could be used for the effective enrichment and sensitive detection of poisons in several oily matrix and has the grate potential application in emergency response and public safety. [ABSTRACT FROM AUTHOR]

Development of analytical methods allowing sensitive detection of neurotransmitters in various biofluids is vital. However, limitations of these methods include interference of impurities and stringent requirements concerning sample purity. In the current work, we developed a strategy for the rapid and sensitive analysis of dopamine (DA) in various biofluids with a smart surface-enhanced Raman spectroscopy (SERS) probe composed of magnetite Fe3O4 and Au nanoparticles (Fe3O4/Au NPs). Besides the simple and quick separation of DA from the specimen, Fe3O4 not only enabled a specific chemical interaction with DA molecules, but also acted as a SERS substrate capable of electromagnetically enhancing the Raman signal of DA. Therefore, the Fe3O4/Au NP composite with its coexisting electric-field effect and charger transfer (CT) enhancement was found to be beneficial for capturing the target molecules in biological environments and then enhancing the DA sensitivity. To understand the strong binding interaction between Fe3O4/Au and DA, X-ray photoelectron spectroscopy (XPS) was carried out, specifically to illuminate the chemical adsorption or possible CT complex. Moreover, a rapid purification strategy for further separating DA from serum was developed, and thus a high nanometer-level sensitivity was achieved. In addition, the feasibility of using Fe3O4/Au combined with the developed purification method was also verified using various tissue homogenates spiked with DA molecules. Such a nanocomposite can offer the possibility of efficiently separating DA from the complex specimen and then providing the sensitive detection of DA for various tissues. Accordingly, the smart SERS Fe3O4/Au nanocomposite probe, with its advantages of simple pre-treatment and synergetic enhanced mechanisms, shows great promise for the rapid and sensitive detection of DA in complicated specimens. [ABSTRACT FROM AUTHOR]

A novel long-period and high-stability 3D hotspot matrix was constructed with the assistance of glycerol based on our previous study on the dynamic-SERS approach in the water system: it could increase efficient hotspot duration from few seconds to twenty minutes and strongly improve sensitivity and reproducibility for SERS detection. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we developed cysteamine-modified surface-enhanced Raman scattering (SERS) substrate for detecting detect trace amount of acidic pigment that shows weak affinity with gold nanoparticles (Au NPs). To realize sensitive and reproducible detection of pigment with weak affinity, the SERS substrate was prepared by attaching cysteamine (CA) to the Au NPs, the acidic pigment molecule could rapidly reached to the surface of Au NPs because of the formation of multi‑hydrogen-bond and electrostatic interaction between the pigment and CA molecule. The proposed method allowed us to detect five kinds of acidic pigment with a limit of 1.0 ppm, which is below the strictest safety limit. Compared with the previous methods, the advantages of the present substrate were its simple substrate preparation, high reproducibility and good universality. Furthermore, the reliable and enough accurate results had been obtained by using of the proposed substrates in the assay of trace pigment in real samples. Graphical Abstract Unlabelled Image Highlights • The SERS substrate of detecting acidic pigment with weak affinity was conveniently prepared without complicated processes. • The cysteamine-modified SERS substrate was universal to five kinds of acid pigment and exhibited high reproducibility. • The cysteamine-modified SERS substrate holds great promise to detect acidic pigment in real complex fields. [ABSTRACT FROM AUTHOR]

A new adsorbent, Fe 3 O 4 sulfonated magnetic nanoparticle (Fe 3 O 4 -SO 3 H MNP), was developed for heavy metal ions removal from water, which could be effectively separated from the solution owing to the superparamagnetic property. The nanoparticles can be used to remove heavy metal ions due to the additional active site, “sulfo-group”, introduced by the AMPS branches grafted onto the iron oxide. The as-synthesized materials were characterized by SEM, TEM, FT-IR and BET. The FTIR, XPS and Zeta potential were used to describe the adsorption mechanism. The Fe 3 O 4 -SO 3 H MNPs showed rapid removal for Pb 2+ and Cd 2+ with maximum of adsorption capacity of 108. 93 and 80.9 mg/g at 25 °C, respectively. The adsorption isotherms for Pb 2+ and Cd 2+ fitted better with Langmuir than Freundlich models, indicated that the processes of the removal of Pb 2+ and Cd 2+ could follow a kind of similar adsorption manner. The adsorption kinetic was consistent with pseudo-second-order model. Furthermore, the reuse experiments results showed the adsorbent might have potential in treating heavy metal ions pollution in water. [ABSTRACT FROM AUTHOR]

A biocompatible and uniquely defined hydroxyapatite (HAP) adsorption membrane with a sandwich structure was developed for the removal of organic micropollutants for the first time. Both the adsorption and membrane technique were used for the removal of organic micropollutants. The hydrophilicity and hydrophobicity of the HAP adsorbent and membrane were tunable by controlling the surface structure of HAP. The adsorption of organic micropollutants on the HAP adsorbent was studied in batch experiments. The adsorption process was fit with the Freundlich model, while the adsorption kinetics followed the pseudo-second-order model. The HAP membrane could remove organic micropollutants effectively by dynamic adsorption in both aqueous and ethanol solutions. The removal efficiencies of organic micropollutants depended on the solution composition, membrane thickness and hydrophilicity, flow rate, and the initial concentration of organic micropollutants. The adsorption capacities of the HAP membrane with a sandwich structure (membrane thickness was 0.3 mm) were 6700, 6510, 6310, 5960, 5490, 5230, 4980 and 4360 L m −2 for 1-naphthyl amine, 2-naphthol, bisphenol S, propranolol hydrochloride, metolachlor, ethinyl oestradiol, 2,4-dichlorophenol and bisphenol A, respectively, when the initial concentration was 3.0 mg L −1 . The biocompatible HAP adsorption membrane can be easily regenerated by methanol and was thus demonstrated to be a novel concept for the removal of organic micropollutants from both aqueous and organic solutions. [ABSTRACT FROM AUTHOR]

A new uniform-sized CeCO 3 OH nanosphere adsorbent was developed, and tested to establish its efficiency, using kinetic and thermodynamic studies, for fluoride removal. The results demonstrated that the CeCO 3 OH nanospheres exhibited much high adsorption capacities for fluoride anions due to electrostatic interactions and exchange of the carbonate and hydroxyl groups on the adsorbent surface with fluoride anions. Adsorption kinetics was fitted well by the pseudo-second-order model as compared to a pseudo-first-order rate expression, and adsorption isotherm data were well described by Langmuir model with max adsorption capacity of 45 mg/g at pH 7.0. Thermodynamic examination demonstrated that fluoride adsorption on the CeCO 3 OH nanospheres was reasonably endothermic and spontaneous. Moreover, the CeCO 3 OH nanospheres have less influence on adsorption of F − by pH and co-exiting ions, such as SO 4 2− , Cl − , HCO 3 − , CO 3 2− , NO 3 − and PO 4 3− , and the adsorption efficiency is very high at the low initial fluoride concentrations in the basis of the equilibrium adsorption capacities. This study indicated that the CeCO 3 OH nanospheres could be developed into a very viable technology for highly effective removal of fluoride from drinking water. [ABSTRACT FROM AUTHOR]

A novel environment friendly adsorbent, micro–nano hierarchical structured flower-like MgO/MgCO 3 (MHS-MgO/MgCO 3 ), was developed for fluoride removal from water. The adsorbent was characterized and its defluoridation properties were investigated. Adsorption kinetics fitted well the pseudo-second-order model. Kinetic data revealed that the fluoride adsorption was rapid, more than 83–90% of fluoride could be removed within 30 min, and the adsorption equilibrium was achieved in the following 4 h. The fluoride adsorption isotherm was well described by Freundlich model. The maximum adsorption capacity was about 300 mg/g at pH = 7. Moreover, this adsorbent possessed a very wide available pH range of 5–11, and the fluoride removal efficiencies even reached up to 86.2%, 83.2% and 76.5% at pH = 11 for initial fluoride concentrations of 10, 20 and 30 mg/L, respectively. The effects of co-existing anions indicated that the anions had less effect on adsorption of fluoride except phosphate. In addition, the adsorption mechanism analysis revealed that the wide available pH range toward fluoride was mainly resulted from the exchange of the carbonate and hydroxyl groups on the surface of the MHS-MgO/MgCO 3 with fluoride anions. [ABSTRACT FROM AUTHOR]