Understanding Time Dependence on Zinc Metal-Organic Framework Growth Using in Situ Liquid Secondary Ion Mass Spectrometry

An evaluation of static ToF-SIMS analysis of environmental organics

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been extensively used in surface analysis due to its high mass resolution, sensitivity, and mass spectral imaging capabilities. Static ToF-SIMS has mainly been used for solid material analysis; however, its application in environmental organics is limited. During SIMS spectral analysis, relative mass accuracy and measurement repeatability are key factors for obtaining reliable speciation and acquiring chemical insights of the specimens. Herein, we provide an evaluation of four environmentally relevant organic systems, including glyoxal, pyruvic acid, oil-in-water emulsion, and carbon dioxide (CO2) capture solvent (i.e., N-2-ethoxyethyl-3-morpholinopropan-1-amine, EMMPA), to show the spectral measurement repeatability when using static ToF-SIMS. First, sample preparation is essential in acquiring accurate and reproducible results in ToF-SIMS analysis. The mass spectral results show that characteristic peaks observed can be distinguished with reasonable confidence by comparing the observed mass to charge ratios (m/z) to theoretical ones. The statistical analysis of peak areas indicates that the peak area and/or peak height measurement ratios are satisfactory among replicates. Compared with previous studies, the bismuth cluster primary ion beam, namely Bi3 +, has less fragmentation than Bi+. Therefore, Bi3 + is deemed more suitable for organic analysis using static SIMS. Our results show that ToF-SIMS offers a viable approach to study environmental organics including but not limited to aqueous aerosols, wastewater emulsions, and CO2 capture solvents. It is expected that future studies will expand organic speciation with high fidelity due to the continued advancement of SIMS as a sensitive analysis technique.

Secondary Ion Mass Spectral Imaging of Metals and Alloys

Secondary Ion Mass Spectrometry (SIMS) is an outstanding technique for Mass Spectral Imaging (MSI) due to its notable advantages, including high sensitivity, selectivity, and high dynamic range. As a result, SIMS has been employed across many domains of science. In this review, we provide an in-depth overview of the fundamental principles underlying SIMS, followed by an account of the recent development of SIMS instruments. The review encompasses various applications of specific SIMS instruments, notably static SIMS with time-of-flight SIMS (ToF-SIMS) as a widely used platform and dynamic SIMS with Nano SIMS and large geometry SIMS as successful instruments. We particularly focus on SIMS utility in microanalysis and imaging of metals and alloys as materials of interest. Additionally, we discuss the challenges in big SIMS data analysis and give examples of machine leaning (ML) and Artificial Intelligence (AI) for effective MSI data analysis. Finally, we recommend the outlook of SIMS development. It is anticipated that in situ and operando SIMS has the potential to significantly enhance the investigation of metals and alloys by enabling real-time examinations of material surfaces and interfaces during dynamic transformations.

Construction of a novel "self-regenerative" electrochemical biosensor based on metal-organic frameworks and its application to the detection of Mycoplasma ovine pneumonia

This study aimed to prepare a novel "self-regenerative" electrochemical biosensor by successively modifying gold nanoparticles, four-arm polyethylene glycol-NH₂, and NH₂-MIL-53 (Al) (MOF) on the glassy carbon electrode interface. A hairpin G-triplex-mediated DNA (G3 probe) as a part of the mycoplasma ovine pneumonia (MO) gene was loosely adsorbed to MOF. Based on the mechanism of hybridization induction, the G3 probe could effectively detach from the MOF only after introducing the target DNA. Subsequently, its guanine-rich nucleic acid sequences were exposed to solution of methylene blue. As a result, the diffusion current of the sensor system showed a sharp decline. The developed biosensor showed excellent selectivity, and the concentration of target DNA exhibited a good correlation in the range 10^-10 to 10^-6 M with a detection limit of 1.00 pM (S/N = 3), even in 10% goat serum. Most interestingly, this biosensor interface automatically started the regeneration program. Moreover, regeneration could be effectively achieved at least seven times, and the recovery rate of the electrode interface and sensing efficiency was up to 90%. Additionally, this platform could be used for other clinical assays in various systems by simply changing the DNA sequence of the probe.

SERS and fluorescence detection of circulating tumor cells (CTCs) with specific capture-release mode based on multifunctional gold nanomaterials and dual-selective recognition

Herein, a dual-selective recognition and multi-enhanced surface-enhanced Raman scattering (SERS)-fluorescence dual mode detection platform is designed for the detection of circulating tumor cells (CTCs). The gold nanoflowers (AuNFs) substrate was synthesized and the CTCs were captured on the surface area of AuNFs/ITO substrate by aptamers modified. At the same time, the novel nanoprobe was designed, anti-EpCAM (AE) and trigger DNA were modified onto the surface of gold nanostars (AuNSs) through a PEG linker. The novel nanoprobe identified CTCs through the specific recognition reaction between AE and the cell epithelial adhesion molecule of the CTCs. The dual-recognition cellular mechanism of the aptamers and AE improves selectivity. Then, the complementary sequence (CS) hybridize with aptamers to release the captured CTCs into the culture medium. The number of CTCs released was detected by SERS and fluorescence. The limit of SERS detection was 5 cells/mL with a linear relationship from 5 to 200 cells/mL. The limit of fluorescence detection was 10 cells/mL with a linear relationship from 10 to 200 cells/mL. Thus, the developed CTCs detection platform demonstrates promising applications for clinical diagnosis.