Reference Materials Research Articles

Analysis of the Ag M4,5 EELS edge to study silver nanoparticle corrosion.

Electron energy loss spectra collected from fresh and corroded silver nanoparticles are compared with those from a number of reference materials, focusing on the M4,5 edge. Chemical shifts and changes in the energy loss near edge structure (ELNES) are described and found to be sufficient to distinguish metallic silver from chemically oxidised silver. The measurements, in conjunction with electron energy loss spectrum imaging, are used to assess the mechanisms for atmospheric corrosion of silver nanoparticles. We unambiguously assign the corrosion product under atmospheric conditions to be silver sulphide, but show the reaction process to be distinctly inhomogeneous, producing a variety of types of corroded particles. LAY DESCRIPTION: >Here, we use analytical electron microscopy to track the corrosion of silver nanoparticles and present chemical maps of the corrosion products. We show clear spectroscopic differences between metallic and corroded silver using the M4,5 electron energy loss spectral feature, which is not commonly studied. Our study shows that corrosion is due to interactions with sulphur in the atmosphere; and the corrosion is not uniform, but appears to develop from specific points on the surface of the nanoparticles.

Light Element (C, N, O) Quantification by EDXS: Application to Meteorite Water Content and Organic Composition.

Quantifying light elements such as carbon, nitrogen, and oxygen in a transmission electron microscope (TEM) is a challenging however essential task in biology, materials, or earth and planetary sciences. We have developed an approach that allows precise quantification by energy-dispersive X-ray spectroscopy (EDXS), using sensitive windowless silicon drift detectors and homemade Python routines for hyperspectral data processing. K-factors were determined using wedge-shaped focused ion beam sections. To correct for X-ray absorption within the sample, the sample mass thickness is determined by the-revisited-two-lines method (Morris, 1980). No beam current measurement is required. Applying this method to the K and L lines of iron, we found that the tabulated mass absorption coefficient at the energy of the iron L lines was too low. This is due to X-ray self-absorption at the iron edge. Using reference material, we experimentally determined an absorption coefficient that gave the expected results. We then analyzed the complex phyllosilicate mixture of the Orgueil meteorite. We show that the N/C ratio of organics can be obtained with an accuracy better than 5 at.% and that oxygen can be quantified accurately enough to infer the hydroxyl content of phyllosilicates.

Assessment of Natural Reference Materials for U‐Pb Geochronology of Grossular‐Andradite Garnet

Garnet U‐Pb dating by laser ablation‐inductively coupled plasma‐mass spectrometry requires the development of matrix‐matched reference materials of variable chemistry and U mass fraction for accurate analysis. Additional calibration of existing primary reference materials is also justified based on the relatively poor calibration of some of the widely available primary reference materials that are currently utilised by the geoscience community. We present a micro sampling workflow combined with a refined ID‐TIMS methodology for the generation of high precision (~ 0.1%) U‐Pb dates from domains within garnet single crystals. Using this workflow, we calibrated two new natural andradite reference materials, the Jumbo andradite (And99; 110.34 ± 0.03 (0.04) [0.13] Ma, n = 7, MSWD = 1.21) and the Tiptop andradite (And87; 209.57 ± 0.11 (0.13) [0.26] Ma, n = 6, MSWD = 1.39). We also present additional calibration of the widely utilised Willsboro‐Lewis andradite primary reference material (And90; 1024.7 ± 9.5 (9.6) [9.6] Ma (2s; overdispersed), n = 6). Wafers of the Jumbo and Tiptop andradite reference materials are available from the authors upon request.

Simultaneous Bulk‐Rock Elemental and Boron Isotope Ratio Measurement Using LA‐ICP‐MS on Silicate Micro‐Particulate Pellets

We have established a method for the simultaneous measurement of element abundances and boron isotopic compositions of bulk‐rock silicate samples by laser ablation coupled to two different ICP‐MS instruments. Fifteen silicate reference materials were prepared as micro‐particulate pressed powder pellets (MP) for analysis. Approximately 1/5th of the ablated material was transported to a single‐collector ICP‐MS for elemental measurement, while 4/5ths were sent to a multi‐collector ICP‐MS for boron isotope ratio measurement. Compositions of different milling materials (agate, zirconium oxide, tungsten carbide, sintered corundum and silicon nitride) were measured for the evaluation of potential contamination during sample preparation. Determined element mass fractions are in agreement with literature values within ±20%. For boron isotope ratios, the matrix‐dependent background elevation across the m/z from 9.9 to 11, and the effect of ablation mass was quantified. Measured δ11B values of most reference materials are consistent with literature values within ±1‰. The intermediate measurement precision is ±0.3‰ for JB‐2 with 30 μg g−1 B and ±0.4‰ for JA‐2 with 21 μg g−1 B. A publically available, web‐based streamlit app was developed for data processing (https://zenodo.org/doi/10.5281/zenodo.11150471). This paves the way for combined, accurate and precise elemental and boron isotope ratio measurements of geological materials.

Garnet Reference Materials for In Situ Lu‐Hf Geochronology

In situ garnet Lu‐Hf geochronology has the potential to revolutionise the chronology of petrological and tectonic processes, yet there is a paucity of well‐characterised reference materials to account for laser‐induced matrix‐dependant elemental fractionation. Here, we characterise two reference garnets GWA‐1 (Lu ~ 7.0 μg g−1) and GWA‐2 (Lu ~ 8.5 μg g−1) for in situ garnet Lu‐Hf geochronology. Isochron ages from isotope dilution Lu‐Hf analyses yield crystallisation ages of 1267.0 ± 3.0 Ma with initial 176Hf/177Hfi of 0.281415 ± 0.000012 (GWA‐1), and 934.7 ± 1.4 Ma with 176Hf/177Hfi of 0.281386 ± 0.000013 (GWA‐2). In situ Lu‐Hf analyses yield inverse isochron ages up to 10% older than the known crystallisation age due to matrix effects between garnet and reference glass (NIST SRM 610) under different instrument tuning conditions. This apparent age offset is reproducible for both materials within the same session and can be readily corrected to obtain accurate ages. Our results demonstrate that GWA‐1 and GWA‐2 are robust reference materials that can be used to correct for matrix‐analytical effects and also to assess the accuracy of in situ Lu‐Hf garnet analyses across a range of commonly encountered garnet compositions.

Quantitative Measurement of Multiple Elements in Micro‐Quantities of Crude Oil Using In Situ Analysis by Laser Ablation‐ICP‐MS

Multi‐element quantification in small amounts of material and in situ measurements at the micrometre scale are essential aspects of geological sample investigation. A direct and rapid simultaneous multi‐elemental determination of metals in crude oil samples was carried out by combining direct laser ablation of the oil inserted in silica capillaries with inductively coupled plasma‐mass spectrometry. The accuracy of LA‐ICP‐MS determination was demonstrated by analysing CONOSTAN reference material oils, certified for multiple elements, and by comparing LA‐ICP‐MS measurement results with those obtained by ICP‐OES using microwave‐assisted sample digestion. The results obtained by both methods were in agreement with certified values. The LA‐ICP‐MS method showed an adequate precision with a mean relative standard deviation of less than 10% for multi‐element determination, and was sufficiently sensitive to determine the majority of elements. LA‐ICP‐MS was also applied to the determination of elements in crude oils of different origins. LA‐ICP‐MS is a good alternative method allowing the determination of elements in organic fluids (oil and bitumen) in shorter times, involving less material consumption, smaller test portion size and with higher throughput compared with protocols using, for instance, sample digestion. It validates the possible application of metal analysis in hydrocarbon‐containing fluid inclusions for metallogenic purposes.

Innovative Use of Carbon Nanotubes in Electrochemical Sensors for the Analysis of Europium in Samples from the Environment

An adsorptive stripping voltammetric method for the determination of trace europium(III) based on the adsorption of europium(III)−cupferron complex on the multiwall carbon nanotubes/spherical glassy carbon (MWCNTs/SGC) electrode modified with a lead film is presented. The method was optimized with respect to the main electrochemical parameters that affect the voltammetric determination (supporting electrolyte, pH, cupferron concentration, deposition potential and time). The calibration graph is linear from 5 × 10−9 to 5 × 10−7 mol l−1 with a correlation coefficient of 0.9993 for europium for a preconcentration time of 80 s. The detection limit for a preconcentration time of 80 s is as low as 1.3 × 10−9 mol l−1 for europium. To confirm the effectiveness of the developed procedure on the MWCNTs/SGC electrode, tests were also carried out on a glassy carbon electrode to compare the detection limits obtained. The developed procedure was tested for the effect of extraneous substances on the europium signal. The proposed method was successfully applied by studying natural samples and certified reference materials.

Method development for multielement determination of halogens and sulfur in teas

Abstract Microwave-induced combustion was evaluated as a sample preparation method for several types of tea (black, green, lemon balm, boldo, and mint) for further determination of bromine, chlorine, fluorine, iodine, and sulfur by ion chromatography. Parameters such as the sample mass efficiently decomposed and the most suitable absorbing solution (ultrapure water and 25, 50, 100, and 150 mmol L−1 NH4OH) were evaluated, considering the characteristics of the analytes and the determination technique used. The maximum sample mass possible to be decomposed was 900 mg of milled tea in the form of pellets, and the absorbing solution chosen was 100 mmol L−1 NH4OH, which provided suitable stabilization of the analytes (recoveries between 95 % and 103 %). To assess the accuracy of the proposed method, a certified reference material (BCR 060, aquatic plant) was analyzed. Agreements with the certified values ranged from 101 % to 107 %. The proposed method was used to analyze tea samples and the concentrations ranged from 549 to 2,549 mg kg−1 for chlorine, 223 to 828 mg kg−1 for fluorine, and 786 to 4,023 mg kg−1 for sulfur; bromine and iodine concentrations were below the limits of quantification (42 and 80 mg kg−1, respectively) in all evaluated samples.

Learning styles, approaches and academic performance of second and third-year medical students of a medical college of Kathmandu: a descriptive cross-sectional study

Background: The research is based on a questionnaire to study the different learning styles among medical students, and their approach to intellectual development. Methods: This is an observational, cross-sectional study conducted on 140 participants. Initially after the informed consent process, the second-year and third-year medical students were requested to respond to the questionnaire without consulting friends. Data were analyzed descriptively and comparison was made. Results: In this study, the students were mostly visual learners, followed by solo learners, audio learners, verbal learners, and social learners. The majority of the students in our study (84.56%) studied less than 4 h per day beyond normal lecture hours. Similarly, 45.71% of students studied continuously for 30–60 min. During break, 63.57% of students used social media, watched television, and videos, and listened to music. Most students (75%) preferred to study in a hostel room and only 12.85% used the library as their study place. The majority of the students (65.71%) of students slept between six to eight hours. The University’s suggested medical textbooks and reference materials were consulted by 94.3% of the students. The 47.85% of students favored self-directed learning with 56.42% preferring to read and write to retain the learned materials. Self-prepared notes were commonly used by the majority of students (60.7%). Conclusions: This research evaluates the preferred learning preferences of medical students and their relationship to academic performance, which will improve the effectiveness of teaching and learning between teachers and medical students.

Qualitative and quantitative analysis of synthetic cannabinoids in e-liquids by pyrolysis–gas chromatography/mass spectrometry

Synthetic cannabinoids (SCs) are a series of synthetic substances that mimic the effects of natural cannabis and cause more serious toxicity and public safety issues. SCs, with a wide variety and fast update rate have become the most abused family of new psychoactive substances. A pyrolysis–gas chromatography/mass spectrometry method has been developed to qualitatively and quantitatively analyze SCs in e-liquids using pyrolysis products as analytical targets, which can effectively expand the detection range of SCs. In qualitative analysis, diluted e-liquids were pyrolyzed in the microfurnace at 800, 600, and 300 ℃, respectively, followed by separation and analysis through gas chromatography/mass spectrometry. SCs in the e-liquids were determined by both shared and characteristic pyrolysis products combined with the EI mass spectrometry of their parent compounds. ADB-BUTINACA and 5F-MDMB-PICA were successfully identified in five e-liquid samples seized by local police. Furthermore, five popular SCs in the illegal market, ADB-BUTINACA, 4F-ABUTINACA, 4CN-CUMYL-BUTINACA, 4F-MDMB-BICA, and 5F-MDMB-PICA, were quantitatively analyzed based on their characteristic pyrolysis products as the analysis targets. The results indicated that the linear range of ADB-BUTINACA was 2–200 μg/mL, while those of 4F-ABUTINACA and 4CN-CUMYL-BUTINACA were 1–200 μg/mL. For 4F-MDMB-BICA and 5F-MDMB-PICA, the linear range was 5–500 μg/mL. The linear correlation coefficients of determination of five SCs were greater than 0.994. The limit of detection (S/N=3) for five SCs was 0.25–2.50 μg/mL, and the limit of quantification (S/N=10) was 0.50–5.00 μg/mL. This quantitative method was applied to five positive samples in real cases. The results showed that the concentrations of ADB-BUTIANCA and 5F-MDMB-PICA in the positive samples were 751.32–4810.10 μg/mL and 1109.41 μg/mL, respectively. The current research provides a validated pyrolysis–gas chromatography/mass spectrometry method, with simple pre-treatment, fast operation and wide screening range, to accurately identify and quantify SCs in e-liquid samples without reference materials.

Lithium isotope ratio analysis of geological samples using atomic absorption spectrometry with improved spectral resolution

This study introduces an improved spectrometric method with enhanced precision to determine isotope ratios in geological samples without chromatographic separation. Firstly, the improvement is achieved by increasing the spectral resolution of the spectrometer applied in well-known high-resolution continuum source atomic absorption spectrometry (HR-CS-AAS). The resulting resolving power and linear dispersion of the upgraded setup, which is denoted in the following as HR + CS-AAS, is well adapted to the line widths of the Li isotope components we investigated. Secondly, our proposed method combines optical absorption spectrometry with machine learning data analysis using an extreme gradient boosting algorithm (XGBoost). This method was applied to analyze certified geological reference materials with δLSVEC(7Li/6Li) (hereafter δ7Li) values ranging from −0.5 ‰ to 4.5 ‰. With a pixel related optical resolving power of λ/∆λ ≈ 780,000, we obtain precisions in δ7Li measurements from 1.0 ‰ to 2.5 ‰. The method is validated by comparing the results with multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), confirming its metrological compatibility. This work presents a fast, robust, and reliable method for δ7Li measurement in geological samples.

A comprehensive gas chromatography electron ionization high resolution mass spectrometry study of a new steroidal selective androgen receptor modulator (SARM) compound S42.

The synthetic 20-keto-steroid S42 (1) demonstrated selective androgen receptor modulator (SARM) properties in preclinical studies and, consequently, received growing attention also in the context of sports drug testing programs. Fundamental understanding of the behavior of S42 (1) and of relevant derivatives in gas chromatography-electron ionization MS experiments at high resolution (GC-EI-HRMS) is indispensable to develop a reliable qualitative and quantitative doping control method for S42 (1) and its metabolites in body fluid matrices. We present important fundamental mechanistic data on the EI fragmentation behavior of S42 (1) and of silyl ether derivatives as well as of stable isotope-labelled reference material.

An Analytical Method for Quantification of Sn Isotope Variations in Geological Materials Using MC‐ICP‐MS

A robust analytical method is presented here, for measurements of Sn isotope variations with high precision using a multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS). A silicate rock dissolution procedure was used, together with means to remove organic matter introduced by the resin during ion‐exchange chromatography. The two‐stage ion exchange chromatography efficiently isolates Sn from the matrix and isobarically interfering elements, from samples with variable Sn mass fractions (~ 0.03 to 7 μg g−1). A double spike technique was also implemented to correct any secondary mass bias induced during sample processing and isotope ratio measurements. An intermediate precision (2s) of ± 0.47 was obtained for ε122/118Sn (using internal normalisation; n = 70 over a period of 29 months), ± 0.021‰ for δ122/118Sn (using double spike; n = 176 over a period of 29 months) and ± 0.059‰ for δ122/118Sn (using Sb doping; n = 34 over a period of 4.5 months) for the Sn standard solution, NIST SRM 3161a (Lot# 140917). The δ122/118SnNIST SRM 3161a of eleven geological reference materials are reported for the first time (BIR‐1a, BRP‐1, DTS‐2b, ECRM 782‐1, JP‐1, OKUM, QLO‐1a, RGM‐2, SGR‐1b, STM‐2 and UB‐N), with five others (AGV‐2, BCR‐2, BHVO‐2, GSP‐2 and W‐2a) showing similar results to previous studies, generally with improved precision. The intermediate precision (2s) of replicate dissolutions of ten RMs (AGV‐2, BCR‐2, BHVO‐2, BIR‐1a, DTS‐2b, GSP‐2, OKUM, SGR‐1b, STM‐2 and W‐2a) varied from 0.003 to 0.054‰. Typical repeatability precision (2SE) of individual measurements of these ten RMs over multiple measurement sessions varied from 0.031 to 0.297‰ (with 120Sn+ beam intensity < 2.37 V) and 0.017 to 0.025‰ (with 120Sn+ beam intensity > 2.37 V).

Preparation and certification of benzoic acid reference material for calorimetry analysis

Benzoic acid reference material is indispensable for bomb calorimeter instrument calibration and validation of gross calorific value (GCV) analysis of any substance. In this work, we demonstrated the preparation of benzoic acid reference material through a homogeneity study, round-robin analysis, and stability study. Two-factor analysis of variance (ANOVA) test for gross calorific value in the randomly selected sub-samples of benzoic acid exhibits a lower FTS value than the Fcrit value, indicating that the samples are sufficiently homogeneous. The calculated uncertainty of between-bottle (ubb) and uncertainty of homogeneity (uhom) for GCV of benzoic acid in the sub-samples were found as 1.82 and 4.42 ​cal/g respectively. We found that the observed homogeneity (uhom (Finding)) value is lower than the assumed homogeneity (uhom (Assume)) value for the prepared benzoic acid reference material. Overall observations confirm that the sub-samples are sufficiently homogeneous. Moreover, the round-robin analysis/or inter-laboratory comparison analysis was conducted to assign the gross calorific value and determine the characterization uncertainty. The seventh order of Grubbs' analysis was done using robust estimator Alogoritm A to assign the GCV of benzoic acid. Finally, the measurement uncertainty of the assigned GCV of benzoic acid was calculated with the combined uncertainties from various sources.

Exploring the Influence of Academic Self-Efficacy on Students' Professional Identity: The Intermediary Role of Social Media Frequency

In recent years, social media has become more and more integral to Chinese daily life as new media has grown and developed. Previously, there were a number of challenges because of the lack of knowledge regarding social media usage and the problems of university students' majors. These challenges include whether the frequency of social media use affects daily learning, the extent to which university students in the new era understand the current state of their majors, whether frequent use of social media supports their studies and the mediating role of social media in these processes. Given these issues, the existing literature lacks comprehensive reference materials. In order to further examine students' learning habits, this study uses a questionnaire survey and a five-point Likert scale to investigate how ASE affects university students' major identification and how social media usage frequency acts as a mediating factor. Based on participants' moderate social media usage frequency, the results suggest a reasonable association between the frequency of social media use and its impact. There is a modest mediation influence of social media, variations in the academic self-efficacy (ASE) of participants, and a substantial positive association between the major identity and self-efficacy of university students.

Accurate non-ceruloplasmin bound copper: a new biomarker for the assessment and monitoring of Wilson disease patients using HPLC coupled to ICP-MS/MS.

Assessment of Wilson disease is complicated, with neither ceruloplasmin, nor serum or urine copper, being reliable. Two new indices, accurate non-ceruloplasmin copper (ANCC) and relative ANCC were developed and applied to a cohort of 71 patients, as part of a Wilson Disease Registry Study. Elemental copper-protein speciation was developed for holo-ceruloplasmin quantitation using strong anion exchange chromatography coupled to triple quadrupole inductively coupled plasma mass spectrometry. The serum proteins were separated using gradient elution and measured at m/z 63 (63Cu+) and 48 (32S16O+) using oxygen reaction mode and Cu-EDTA as calibration standard. The ANCC was calculated by subtraction of the ceruloplasmin bound copper from the total serum copper and the RelANCC was the percentage of total copper present as the ANCC. The accuracy of the holo-ceruloplasmin measurement was established using two certified reference materials, giving a mean recovery of 94.2 %. Regression analysis between the sum of the copper containing species and total copper concentration in the patient samples was acceptable (slope=0.964, intercept=0, r=0.987) and a difference plot, gave a mean difference for copper of 0.38 μmol/L. Intra-day precision for holo-ceruloplasmin at serum copper concentrations of 0.48 and 3.20 μmol/L were 5.2 and 5.6 % CVand the intermediate precision at concentrations of 0.80 and 5.99 μmol/L were 6.4 and 6.4 % CV, respectively. The limit of detection (LOD) and lower limit of quantification (LLOQ) for holo-ceruloplasmin were 0.08 and 0.27 μmol/L as copper, respectively. ANCC and Relative ANCC are important new diagnostic and monitoring biomarker indices for Wilson disease (WD).

Process Parameter Optimisation in Laser Powder Bed Fusion of Duplex Stainless Steel 2205

Additive Manufacturing (AM) appears as a very interesting alternative to conventional production routes for alloys and metals, thanks to the fact that at the end of printing, the final product is obtained directly. The present article looks for the inclusion of duplex stainless steel 2205 (DSS-2205) in the commercial catalog of steels utilized in powder bed fusion (PBF) technologies, specifically applying the selective laser melting (SLM) technique. The main objective is to establish optimal printing parameters that reproduce the closest results to the base material properties. To achieve this, the response surface method was used in the methodology and experimental design, studying the parameters of laser power, scanning speed, and hatching distance. A reference material, machined from a hot-rolled plate, was utilized to compare the results obtained through tensile strength. Lastly, the optimal parameters have been obtained for this stainless steel. Additionally, a study of heat treatments has been developed, aiming to optimize the austenitization process, achieving an improvement in mechanical properties. A steel with mechanical properties practically identical to those of steel produced using conventional techniques has been obtained through SLM.

Development of a Rapid Analytical Method on UV Spectrophotometer for Analysis of Trace Level APIs Telmisartan in Cleaning Validation Sample

Since the 1990’s, cleaning validations have gained a lot of interest within pharmaceutical and bio-pharmaceutical companies. In 1988, the FDA experienced its first major incident with cross contamination traceable to inadequate cleaning and cleaning validation. The finished drug product, Cholestyramine Resin USP, was recalled due to contamination with low levels of intermediates and degradants from the production of agricultural pesticides. The cross-contamination was believed to have come from the use of drums in the production of the active pharmaceutical ingredient (API). These drums had previously been used to store solvents for the manufacture of agricultural pesticides at another plant. Extra pure methanol procured from Chempura Enterprises Indore of make Merck and Analytical Grade water procured from the SK Traders Indore M.P. Reference materials, Telmisartan from Axiom Analytical Services Indore M.P. HPLC grade methanol (MeOH), HPLC Grade Water were purchased from Chempura Enterprises Indore M.P.. All chemicals were used as received, without any further purification. In recent years, increased emphasis has been placed in pharmaceutical companies for implementing robust validated cleaning procedures. The cleaning procedure is one of the most important tasks to avoid contamination and cross- contamination of APIs in pharmaceutical products manufactured on the same equipment trains. The cleaning procedures must be supported byappropriate analytical methods and related sampling methodologies.

Extraction recovery and speciation of selenium in Se-enriched yeast.

The complete characterization of selenium-enriched yeast in terms of selenium species has been the goal of extensive research for the last three decades. This contribution addresses the two outstanding questions: the mass balance of the identified and reported selenium species and the possible presence of inorganic selenium. For this purpose, four procedures have been designed combining, in diverse order, the principal steps of selenium speciation analysis in Se-rich yeast: extraction of the Se-metabolome, derivatization of cysteine and Se-cysteine (SeCys) residues, proteolysis, and definitive Se recovery using SDS extraction, followed by mineralization. The recovery of selenium in each step and its speciation were controlled by ICP MS and by reversed-phase HPLC-ICP MS, respectively. The study, carried out for the SELM-1 reference material, demonstrated the presence of about 10% of inorganic selenium and a serious risk of losses of SeCys during derivatization and proteolysis. As result of our work, we postulate the following values for SELM-1: Se-metabolome fraction (SeMF) 14.8 ± 0.7%; total selenomethionine (SeMet) 66.2 ± 2.7% (including ca. 1.5% SeMet present in the SeMF); total SeCys 12.5 ± 1.5% (including 2% of SeCys present in the Se-MF); total inorganic selenium 9.7 ± 1.7%, accounting for > 99.8% of the selenium.

The Facile Synthesis of Nickel-Doped Composite Magnetic Ni@CoO@ZIF-67 as an Efficient Heterogeneous Catalyst for the Ring-Opening Polymerization of L-Lactide

The ring-opening polymerization of L-lactide is a crucial route for producing biodegradable polylactides (PLAs). Developing an efficient catalyst for this process poses significant challenges. Herein, we report the successful incorporation of nickel during the crystallization of ZIF-67, the derivation of the abundant and stable CoO source, to obtain the composite magnetic Ni@CoO@ZIF-67 using the solid-state thermal (SST) method. The characterization of the resulting materials revealed that nickel atoms are well dispersed in the composite CoO@ZIF-67, imparting additional magnetic properties. The composite Ni@CoO@ZIF-67 demonstrated superior performance as a heterogeneous catalyst for the ring-opening polymerization of L-lactide compared to reference materials such as Ni-Hmim, CoO, ZIF-67, and CoO@ZIF-67. Furthermore, the magnetic property of Ni@CoO@ZIF-67 offers practical advantages, enabling easier separation and recycling of the catalyst. Notably, the SST method facilitates the single-step synthesis of composite magnetic Ni@CoO@ZIF-67 under solvent-free conditions, representing a significant advancement in catalyst development. This approach not only simplifies the synthesis process but also inspires further developments of heterogeneous magnetic catalysts for a variety of effective and diverse reactions.