Fluoride Residue Research Articles

Highly efficient removal and real-time visual detection of fluoride ions using ratiometric CAU-10-NH2@RhB: Probe design, sensing performance, and practical applications

The extensive use of fluoride in agriculture, industry, medicine, and daily necessities has raised growing concerns about fluoride residue. To date, real-time visual detection and efficient removal of fluoride ions from water remain greatly desirable. Herein, nano-CAU-10-NH2@RhB is introduced as a ratiometric fluorescent probe and efficient scavenger for the intelligent detection and removal of fluoride ions. CAU-10-NH2@RhB is readily obtained through one-pot synthesis and exhibits high sensitivity and selectivity for real-time fluoride ion detection, with a naked-eye distinguishable color change from pink to blue. A portable device for point-of-care testing was developed based on color hue analysis readout using a smartphone. A quantitative response was achieved across a wide concentration range, with a detection limit of 54.2 nM. Adsorption experiments suggest that nano-CAU-10-NH2@RhB serves as an efficient fluoride ion scavenger, with a fluoride adsorption capacity of 49.3 mg/g. Moreover, the mechanistic study revealed that hydrogen bonds formed between fluoride ions and amino groups of CAU-10-NH2@RhB are crucial for the detection and adsorption of fluoride ions. This analysis platform was also used for point-of-care quantitative visual detection of fluoride ions in food, water, and toothpaste.

Evaluation of fluoride ion residues in black tea after fumigation with sulfuryl fluoride

Sulfuryl fluoride is a colorless, odorless gas used as a fumigant against pests during the storage of durable agricultural products. It is also one of the alternatives to methyl bromide, which is banned by the Montreal Protocol. During a fumigation, the decomposition product of sulfuryl fluoride residue can also be formed in addition to the sulfuryl fluoride residue. Fluoride is actually a natural ingredient of the tea plant. However, within the growing process of the tea plant fluoride is concentrated in the old leaves when compared with the young shoots. Investigating the variation of the fluoride content in black tea before and after sulfuryl fluoride fumigation is the subject of this study. Three different brands of black teas with different fluoride concentrations purchased from local supermarkets in 2022 were fumigated with approximately 60 g/m3 of sulfuryl fluoride for 24 hours in a 1 m3 fumigation chamber. The AOAC’s recommended method for extraction of fluoride in plants (Method 975.04) was applied in this study. It was compared with the fluoride contents after fumigation in teas (41.4; 165.1 and 329.5 mg/kg, respectively). It is concluded that there is no statistically [t(7)=0,284; t(7)=0,769 and t(7)=1,419 p>0,05] significant difference in fluoride content in teas after fumigation.

Fluoride-treated IM-5 zeolite as a highly active catalyst for the production of jet fuels by the oligomerization of 1-hexene

Light alkenes oligomerization, performed in the presence of solid acid catalysts, is an important alternative for the production of clean jet fuels. For 1-hexene oligomerization, the current catalyst often suffers from low activity and selectivity. The developed process is upgraded by zeolite catalyst, targeting high-concentration of jet-range hydrocarbons. An efficient and selective IM-5 zeolite-derived catalytic system has been developed for the oligomerization of 1-hexene. The treatment in an aqueous NH4F solution led to dealumination without structure degradation. The IM-5 zeolite with a unique two-dimensional IMF structure and 2.5 nm nanoslab showed rapid diffusion ability than ZSM-5 zeolite. Enhance acidities were observed in the NH4F-treated IM-5 zeolites owing to fluoride residue and the removal of Al atoms. The strong Brønsted acid sites exerted a positive effect on both the cracking and the oligomerization reactions with the increasing of the yields of dimers. The contact time and partial pressure between the 1-hexene and the IM-5 zeolites were used to analyze the competition of cracking reactions. High 1-hexene conversion (62%), optimal oligomerization to C3-C5 ratio (O/C = 32), and reasonable stability were obtained over the etched IM-5 catalyst at 240 °C, 4 MPa, and the flow rate of N2 was 50 mL/min.

Safety of Antarctic krill (Euphausia superba) as food source: its initial fluoride toxicity study

Abstract Antarctic Krill, rich in many nutrients, is supposed to be one of the strategic food sources. However, it is not acceptable for direct consumption as traditional food, as its high content of fluoride is harmful to adults and children. Therefore, the safety of fluoride residue in Antarctic krill for food production should be investigated. In this research, the fluoride toxicity in Antarctic Krill was evaluated through mice feeding experiment. Their body weight was found not to be influenced by fluoride. However, dental fluorosis was observed in the krill group and the NaF group. Fluoride content in liver, kidney, urine, and bones are significantly different (P<0.05) among these three groups, which amount to plateau during the first ten days of feeding, except the fluoride in bone which keeps increasing all through the experimental time. Furthermore, less amount of fluoride was determined in the krill group compared with the amount in NaF group, even if they have the same concentration of fluoride. Besides, lesions in livers, kidneys and bones of the two experimental groups were observed through histopathological studies.

Fluoride-modified ZSM-5 for endothermic catalytic cracking of n-decane

Endothermic catalytic cracking of hydrocarbon fuel is a promising technique for active thermal protection of advanced aircrafts. Catalyst with high activity and stability is crucial for obtaining high heat-absorbing capability. Here, a series of fluoride-modified ZSM-5 catalysts (FZ) were prepared and characterized with XRD, SEM, 27Al and 29Si NMR, Ar physisorption, NH3-TPD, XRF and Py-IR. Significant changes in porosity and acidity were revealed on the fluoride-modified samples owing to framework dealumination and fluoride residue. Catalytic and endothermic performances were also investigated in supercritical cracking of n-decane. Good performances with obviously enhanced n-decane conversion and heat sink, and decreased coke deposition were obtained via appropriate fluoride modification.

Influence of Fluoride Ions Contamination in Front Opening Unified Pod (FOUP) Generating Defective Bonding Pad

ABSTRACTWe analyzed defective bonding pad in various ways and determined the causes of defects that boosts oxidation of aluminium by fluoride residue on surface of pad with moisture. Additionally, we compared and evaluated methods to minimize pad defects in aspects such as etching and wafer storage environment. In case of wafers after pad open etching process using common CF4 stored in FOUP, the concentration of fluoride ions in FOUP was 230 ng L–1 and it decreased down to 170 ng L–1 when Ar sputtering step was added after using CF4. Also under the same condition, fluoride ion concentration in FOUP decreased down to 20 ng L–1 when nitrogen purge was introduced for 10 minutes to the FOUP where wafers were stored and the moisture also decreased from 40% before purge to 10% after purge. As a result of observation on pad surface after storing wafers in FOUP for 120 hours under each condition, negligible amount of defects were found when nitrogen was purged. Therefore, we conclude that defects on pad were generated by existing fluoride ions after etching process and moisture in the air.

Extraction of uranium from solid waste containing uranium and fluorine

A significant amount of waste residue and adsorbent containing uranium generated by uranium refining and conversion R&D activities has been stored at the Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency. The treatment of these materials is one of the most important tasks in the decommissioning of the plant. These solid wastes also contain significant quantities of fluorine, and it is important to separate this out in order to recover pure uranium as a resource.As one method for separating fluorine from uranium, we have proposed the use of solvent extraction using tri-n-octylamine (TNOA), and silicofluoride (Na2SiF6) precipitation. The decontamination factor of fluorine for solutions, prepared by dissolving spent sodium fluoride (NaF) and uranium tetrafluoride (UF4) residue into sulfuric acid, became 5.2 and 6.6 respectively when the TNOA solvent extraction process was performed. The Na2SiF6 process using SiO2 is more effective in separating fluorine from a solution prepared by dissolving spent NaF and UF4 residue using sulfuric and hydrochloric acid, with the decontamination factor of fluorine being 14 and 28. Uranium remaining in solution after removal of fluorine was recovered as uranium peroxide. The fluorine content of uranium recovered from UF4 by SiO2 treatment was as low as 0.012wt%, and that of uranium recovered from NaF was below 0.0075%. This is in accordance with the target conditions defined by the ASTM standard.

Aqueous Fluoride Residue Removers for 32 nm and beyond Copper Ultra Low-κ Technologies

Mallinckrodt Baker, Inc. (MBI) has developed an aqueous fluoride-based cleaner (AFC1) that shows improved ultra-low k (ULK) and cobalt tungsten phosphide (CoWP) compatibility over dilute hydrofluoric acid (dHF) and a simple solvent based cleaner (SFC1). Performance and compatibility testing was performed with beaker tests at MBI and on 45 nm wafers by GLOBALFOUNDRIES. Our results indicate that AFC1 may be a good alternative to dHF for future Cu technologies.

Removing imperceptible fluoride residue after chemical dry-cleaning to fabricate uniform low-resistance NiSi film

The authors investigated the integrity of the interface between a Ni film and a Si substrate treated by in situ chemical dry-cleaning using ammonium fluorosilicate, or (NH4)2SiF6. In the conventional cleaning scheme, imperceptible fluoride residue at the interface between Ni and Si, even after subliming at 120 °C, was detected by synchrotron x-ray photoelectron spectroscopy. The authors found that the fluoride residue could be removed by additional subliming at 200 °C in a separate chamber following the conventional cleaning scheme (two-step sublimation cleaning). The sheet resistance of nickel monosilicide (NiSi) films fabricated by two-step sublimation cleaning was lower and the NiSi–Si interface was more uniform than for those fabricated by conventional cleaning. This suggests that the fluoride residue triggered the formation of a rough interface between the Ni and Si layers, thus leading to the performance degradation of the NiSi films.

Dissolution Techniques with Microwave Heating Devices for Radiochemical Analysis of Ash and Cement-solidified Product Samples

For the radiochemical analysis of low-level radioactive wastes, a relatively large quantity of sample solutions must be prepared. In order to dissolve incinerated ash (fly ash and bottom ash) of radioactive combustible wastes and cement-solidified products of radioactive liquid wastes, a dissolution method using microwave heating devices was developed. In the present method, most metal elements in samples were extracted with HCl and HNO3 to the sample solution and a precipitate with silica as the main ingredient was decomposed with HF and HNO3. As a result, the fluoride residue was sufficiently reduced and more than 99% of the radionuclides were recovered to the sample solution. The ash and cement-solidified product samples were successfully dissolved in a shorter time compared with that of a conventional method by external heating, because HClO4 with a high boiling point and having much time for heating to dryness was not used.

Effects of fluoride residue on Cu agglomeration in Cu/low- k interconnects

We have investigated the effects of fluoride residue on the thermal stability of a Cu/barrier metal (BM)/porous low- k film ( k < 2.3) structure. We confirmed that the Cu agglomerated more on a BM/inter layer dielectric (ILD) with a fluoride residue. To consider the effect of fluoride residue on Cu agglomeration, the structural state at the Cu/BM interface was evaluated with a cross-section transmission electron microscope (TEM) and atomic force microscope (AFM). And the chemical bonding state at the Cu/BM interface was evaluated with the interface peeling-off method and X-ray photoelectron spectroscopy (XPS). Moreover, we confirmed the oxidation of Cu with fluoride in accelerated conditions to clarify the effect of fluoride on Cu. Our experiments suggested that the fluoride residue led to the formation of a metal fluoride, and this accelerated the Cu agglomeration accompanying an increase in Cu oxidation.

Aqueous Based Single Wafer Cleaning Process Development and Integration into 65nm Process Flow using Metal Hard Mask

AbstractAs the industry develops processes for the 65 and 45 nm technology nodes, post etch/ash cleaning faces new challenges with far more stringent requirements on surface cleanliness and materials loss. The introduction and integration of new materials, such as metal hard mask, creates additional requirements for wafer cleaning due to the occurrence of new defect modes related to metal hard mask. These include organometallic residue and metal fluorite compounds precipitating with time. We have developed a novel aqueous solution (AQ) based single wafer cleaning process to address these new defect modes. Physical characterization results and process integration electrical data and reliability data (TEM cross section review of the vias) are presented in this paper.The main conclusions can be summarized as follows: (1) In the dual damascene Cu/low-k process flow with hard mask, there are three typical residues after etch/ash: generic polymer residue, organometallic residue strongly bonded to metal maks, and time-dependent metal fluoride residue. (2) Generic polymer residue is very well characterized [1,2] and is usually easy to remove with solvent or aqueous solution [2,3]. (3)We developed an oxidizing chemistry based process to undercut the hard mask for the organometallic residue removal, which proved highly effective. (4)The time-dependent metal fluoride reside makes queue time control after etch/ash very critical (&lt;1 hour). We developed a process with a fluorine based aqueous chemistry to address the metal fluoride residue, which proved highly effective. With this new process, queue time control is not required. (5) The post etch/ash cleaning for the Cu/low-k structure with metal hard mask typically employs the solvent/dry plasma ash multi-step procedure [4]. The new process developed in this research reduced the multi-step process to one wet clean step with two different aqueous chemistries in sequence. (6) The integration electrical data shows that the new single step aqueous cleaning process performance is comparable to, or even better than that from the solvent/dry plasma ash multi cleaning process. (7) Blanket Cu loss with the new process is about 23A/min, however TEM analysis of the vias after full integration shows Cu loss, we are working to improve the integration related Cu loss.

Determination of low concentrations of platinum group elements in geological samples by ID-ICP-MS

Accurate and precise determination of platinum group elements (PGEs) at ppb concentrations in geological samples is important but problematic. This paper reports an improved analytical method for the determination of Pt, Pd, Ru, Ir and Rh at sub-ppb levels by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICP-MS). Prior to experimentation, all reagents were carfully purified: HBO3, HCl and SnCl2 by Te coprecipitation and HNO3 and HF by subboiling distillation. HF, HNO3 and HCl were used to decompose 10 gram sample. The fluoride residue from the acid digestion is minimized by using H3BO3 for complexation, thus mini-fusion of sodium peroxide can be performed in corundum crucibles instead of bulk Na2O2 fusion to lower blank level. The solution of acid digestion and Na2O2 fusion are combined and PGEs are then pre-concentrated by Te coprecipitation. Cu, Ni, Zr and Hf are removed using cation exchange resin and P507 extraction chromatography resin combined in the same column to minimize their interference. Pt, Pd, Ru and Ir are determined using ID-ICP-MS, whereas the mono-isotopic element, Rh, is determined by external calibration using highly enriched 194Pt as the internal standard. The enriched 194Pt spike behaves similar to Rh during the Te precipitation procedure and acts as an ideal internal standard. The determination limits for PGE range from 0.01–0.19 ng g−1. The results obtained using this new method for the CCRMP (CANMET, Ottawa, Canada) certified reference materials WGB-1 (gabbro), TDB-1 (diabase) and UMT-1 (ultramafic ore tailings), show good agreement with the reported values, but have discrepancies compared with the certified values when the concentration of Ru, Rh and Ir below 0.5 ng g−1.

δ18O of Igneous Chromites: An Indicator of Syn- and Post-Magmatic Hydrothermal Interaction

laser and feldspar using a CO2 laser. Chomite was analysed on both systems to test the reaction systematics. In the middle of the reaction a dense covering of fluoride residue forms. This acts as a barrier to the Nd-YAG laser often resulting in incomplete oxygen yields, but is still penetrable by the CO2 laser. Oxygen yields were consistently higher using the C02 system. Microprobe analyses of representative grains from the separates were used to calculate yields of oxygen. Those analyses which give 80-90% yields of oxygen have isotope ratios 0.2-0.3%o lower than the same samples yielding 92-99%o oxygen.

Determination of Boron in Silicate Samples by Direct Aspiration of Sample HF Solutions into ICPMS

A rapid and precise technique for the determination of boron content in silicate rocks was developed by employing isotope dilution inductively coupled plasma mass spectrometry with a flow injection system (FI-ID-ICPMS). The sample was decomposed with HF and mannitol, dried to remove silicon as gas, and redissolved with HF to extract boron from the fluoride residue. Ultimately, the HF solution was directly aspirated into the ICPMS. The total procedural blank was 0.08−0.36 ng. No matrix-induced mass discrimination was observed in the rock solution for dilution factors of up to 110. The present method is capable of determining 1 μg g-1 boron in a 1 mg silicate rock sample with blank correction of <20%. Replicate analyses of USGS rock standards, PCC-1, BCR-1, and AGV-1, and GSJ rock standards, JB-1, JB-2, JB-3, JA-1, JA-2, and JA-3, yielded reproducibilities (RSD) of <2%. These results were identical with those obtained by ID thermal ionization mass spectrometry within the analytical errors. These results indicate that the present method allows the precise determination of the boron content in a small sample of silicate materials with simple handling, resulting in the extremely low procedural blank of boron.

Residue adsorption—III: Mutual separation of 227Ac, 227Th and 223Ra

227Ac, 227Th and 223Ra can be separated from each other with good yield and radiochemical purity by adsorption on platinum followed by selective desorption. The three nuclides are deposited on Pt by evaporation from aqueous HF, HNO 3 or NH 4NO 3 solutions. The 223Ra is only partially soluble in H 2O but can be quantitatively desorbed by dilute mineral acids or their ammonium salt solutions. Desorption with 0·01 N HF is preferred because it has the least tendency to disturb the 227Ac and 227Th fluorides in the residue. A fluoride residue containing 227Ac and 227Th can be leached repeatedly with 0·01 N HF to recover 223Ra; however, because of alpha recoil, about half of the ingrown 223Ra cannot be desorbed with dilute HF. Evidence is presented indicating that metathesis of the fluoride residue converts the Ac(III) to a double salt with ammonium nitrate. Elimination of the NH 4NO 3 by sublimation yields a basic 227Ac nitrate which can be desorbed by 0·1 N NH 4NO 3 but not by H 2O. Under the conditions described, 227Th remains adsorbed as an oxide or basic nitrate, while 227Ac is quantitatively desorbed.