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The variation among individual cells plays a significant role in many biological functions. Single-cell analysis is advantageous for gaining insight into intricate biochemical mechanisms rarely accessible when studying tissues as a whole. However, measurement on a unicellular scale is still challenging due to unicellular complex composition, minute substance quantities, and considerable differences in compound concentrations. Mass spectrometry has recently gained extensive attention in unicellular analytical fields due to its exceptional sensitivity, throughput, and compound identification abilities. At present, single-cell mass spectrometry primarily concentrates on the enhancement of ionization methods. The principal ionization approaches encompass nanoelectrospray ionization (nano-ESI), laser desorption ionization (LDI), secondary ion mass spectrometry (SIMS), and inductively coupled plasma (ICP). This article summarizes the most recent advancements in ionization techniques and explores their potential directions within the field of single-cell mass spectrometry.

Rice is one of the popular foods in the world, and the identification and measurement of the concentration of metal elements in therein is necessary for food safety. To this end, this work investigated the feasibility of using laser desorption ionization time-of-flight mass spectrometry (LDI-TOF-MS) for the qualitative identification of metal elements present in rice. The effect of different sample preparation methods (solvation of rice powder in water, acid digestion, and rice tablet) and laser wavelength on the mass spectral pattern of rice was investigated. Based on the experimental results, LDI-TOF-MS proves to be a reliable method for the qualitative identification of the metal elements in rice. It was determined that the rice sample prepared as a tablet and using visible laser radiation, are the most suitable choice for the identification of metallic elements using LDI-TOF-MS. The mass spectrum of rice was experimentally modeled using starch and theoretically simulated. [Display omitted] • Sample preparation method greatly influenced the mass spectral pattern of rice. • The laser Wavelength considerably affected the rice's mass spectrum. • Rice tablet sample yielded the most informative mass spectrum using visible light. • Rice tablet spectrum measured using visible light showed the highest intensity Zn peak. • Mass spectrum of Rice in water showed stronger Fe peak using visible light. [ABSTRACT FROM AUTHOR]

This study evaluates the application of laser desorption ionization high‐resolution mass spectrometry (LDI‐HRMS) to identify coffee components. The coffee analysis was performed based on origins, roasting temperatures, and extraction methods. The LDI‐HRMS experimental results were compared with electrospray ionization (ESI) HRMS analysis, which revealed major compositional differences of coffee ingredients between LDI and ESI data. It was also observed that bitter components in coffee increased with the increasing roasting temperature, and espresso was found to have more carbohydrate‐derived compounds. This study clearly shows that coffee components can efficiently be identified with LDI. Moreover, a more systematic database can be constructed by combining it with LDI‐imaging because LDI is simple, fast, and requires small amount sample consumption. [ABSTRACT FROM AUTHOR]

There is no analytical system to directly and simultaneously detect taste- and odor-active compounds. Graphite carbon black (GCB) nanoparticles, a chemical adsorbent for a variety of compounds, including gaseous molecules, which consists of nanoparticles made from multilayered sheets of sp2-conjugated atomic carbon, have the characteristics required for a surface-assisted laser desorption ionization–mass spectrometry (SALDI-MS) material. Thus, in this study, GCB-LDI-MS was developed for the simultaneous detection of taste- and odor-active compounds. The proposed GCB-LDI-MS successfully detected volatile compounds, including ethyl esters, alcohols, fatty acids, and aldehydes with up to 16 carbons (maximum carbon number of the tested compounds), which could not be detected by conventional matrix-assisted-LDI-MS. Moreover, a series of taste-active compounds (e.g., amino acids and sugars) and various volatile compounds (e.g., ethyl esters, aldehydes, alcohols, fatty acids, and lactones) as a mixture in liquid samples were also detected by the present GCB-LDI-MS. Thus, the proposed simple and rapid detection technique can digitize the analysis of flavor compounds, which provides an analytical concept for flavor scanning to evaluate the palatability of food products. [ABSTRACT FROM AUTHOR]

Metabolic analysis in biofluids interprets the end products in the bioprocess, emerging as an irreplaceable disease diagnosis and monitoring platform. Laser desorption/ionization mass spectrometry (LDI MS)‐based metabolic analysis holds great potential for clinical applications in terms of high throughput, rapid signal readout, and minimal sample preparation. There are two essential elements to construct the LDI MS‐based metabolic analysis: 1) well‐designed nanomaterials as matrices; 2) machine learning algorithms for data analysis. This review highlights the development of various inorganic matrices to comprehend the advantages of LDI MS in metabolite detection and the recent diagnostic applications based on target metabolite detection and untargeted metabolic fingerprints in biological fluids. [ABSTRACT FROM AUTHOR]

This study investigates the applicability of six transition metal dichalcogenides to efficient therapeutic drug monitoring of ten antiepileptic drugs using laser desorption/ionization-mass spectrometry. We found that molybdenum ditelluride and tungsten ditelluride are suitable for the sensitive quantification of therapeutic drugs. The contribution of tellurium to the enhanced efficiency of laser desorption ionization was validated through theoretical calculations utilizing an integrated model that incorporates transition-metal dichalcogenides and antiepileptic drugs. The results of our theoretical calculations suggest that the relatively low surface electron density for the tellurium-containing transition metal dichalcogenides induces stronger Coulombic interactions, which results in enhanced laser desorption and ionization efficiency. To demonstrate applicability, up to 120 patient samples were analyzed to determine drug concentrations, and the results were compared with those of immunoassay and liquid chromatography-tandem mass spectrometry. Agreements among these methods were statistically evaluated using the Passing-Bablok regression and Bland-Altman analysis. Furthermore, our method has been shown to be applicable to the simultaneous detection and multiplexed quantification of antiepileptic drugs.

Mass spectrometry imaging (MSI) has become an important analytical tool for the label‐free chemical imaging of diverse molecules in biological specimens. This minireview surveys some emerging methods in the context of factors that can lead to inaccurate information in MSI, chemical and spatial aberrations, along with their common sources. Matrix‐assisted laser desorption ionization, based on organic matrices, has become the most widely used MSI technique for biomolecules. However, due to inherent limitations associated with the use of organic matrices, for example, heterogeneous matrix‐analyte cocrystallization, and spectral interferences due to the matrix, laser desorption ionization (LDI) from inorganic and nanophotonic platforms has emerged as an alternative MSI modality with complementary advantages. In this review, inorganic and nanophotonic platforms for LDI‐MSI, their applications in imaging, notable merits, and limitations are described. [ABSTRACT FROM AUTHOR]

The efficient detection of small molecules is of significance for environmental monitoring, pharmacology, metabolomics, and lipidomics. The laser desorption/ionization mass spectrometry (LDI MS) platform enables high sensitivity, accuracy, resolution, and throughput in molecular analysis, but its analytical capability with respect to small molecules is limited due to inherent drawbacks arising from conventional organic matrices. The selection of an appropriate matrix is thus a precondition for small molecule detection by LDI MS. To date, various inorganic matrices have been developed, with a growing interest in composite materials displaying synergetic effects. This Minireview highlights the development of nanocomposites as LDI matrices driven by numerous innovations in material science, and their emerging use in small‐molecule analysis. [ABSTRACT FROM AUTHOR]

A highly oriented crystalline metal-organic framework (MOF) nanofilm array was prepared and used for surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) for determination of small molecules. The MOF nanofilm was characterized using scanning/transmission electron microscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. Different small molecules (anthracene, n-eicosanoic acid, Rhodamine B) were successfully determined by this MOF nanofilm array with limits of detection (LOD) between 0.1–5 ng·mL−1 and limits of quantification (LOQ) between 1 and 10 ng·mL−1. Compared to previously reported MOF-based SALDI-MS, this array exhibits better reproducibility (3.3–5.2%) and recovery (89–105%). The intensity of the MS peak remains the same after 25 repeated cycles. This indicates good repeatability. This MOF nanofilm-based SALDI-MS array can be used for determination of fatty acid and Rhodamine B in real samples with good recovery (83–106%). [ABSTRACT FROM AUTHOR]

Mass spectrometry imaging (MSI) is used increasingly to simultaneously detect a broad range of biomolecules while mapping their spatial distributions within biological tissue sections. Matrix‐assisted laser desorption ionization (MALDI) is recognized as the method‐of‐choice for MSI applications due in part to its broad molecular coverage. In spite of the remarkable advantages offered by MALDI, imaging of neutral lipids, such as triglycerides (TGs), from tissue has remained a significant challenge due to ion suppression of TGs by phospholipids, e.g. phosphatidylcholines (PCs). To help overcome this limitation, silicon nanopost array (NAPA) substrates were introduced to selectively ionize TGs from biological tissue sections. This matrix‐free laser desorption ionization (LDI) platform was previously shown to provide enhanced ionization of certain lipid classes, such as hexosylceramides (HexCers) and phosphatidylethanolamines (PEs) from mouse brain tissue. In this work, we present NAPA as an MSI platform offering enhanced ionization efficiency for TGs from biological tissues relative to MALDI, allowing it to serve as a complement to MALDI‐MSI. Analysis of a standard lipid mixture containing PC(18:1/18:1) and TG(16:0/16:0/16:0) by LDI from NAPA provided an ~49 and ~227‐fold higher signal for TG(16:0/16:0/16:0) relative to MALDI, when analyzed without and with the addition of a sodium acetate, respectively. In contrast, MALDI provided an ~757 and ~295‐fold higher signal for PC(18:1/18:1) compared with NAPA, without and with additional Na+. Averaged signal intensities for TGs from MSI of mouse lung and human skin tissues exhibited an ~105 and ~49‐fold increase, respectively, with LDI from NAPA compared with MALDI. With respect to PCs, MALDI provided an ~2 and ~19‐fold increase in signal intensity for mouse lung and human skin tissues, respectively, when compared with NAPA. The complementary coverage obtained by the two platforms demonstrates the utility of using both techniques to maximize the information obtained from lipid MS or MSI experiments. [ABSTRACT FROM AUTHOR]

Soot (sometimes referred to as black carbon) is produced when hydrocarbon fuels are burned. Our hypothesis is that polynuclear aromatic hydrocarbon (PAH) molecules are the dominant component of soot, with individual PAH molecules forming ordered stacks that agglomerate into primary particles (PP). Here we show that the PAH composition of soot can be exactly determined and spatially resolved by low‐fluence laser desorption ionization, coupled with high‐resolution mass spectrometry imaging. This analysis revealed that PAHs of 239–838 Da, containing few oxygenated species, comprise the soot observed in an ethylene diffusion flame. As informed by chemical graph theory (CGT), the vast majority of species observed in the sampled particulate matter may be described as benzenoids, consisting of only fused 6‐membered rings. Within that limit, there is clear evidence for the presence of radical PAH in the particulate samples. Further, for benzenoid structures the observed empirical formulae limit the observed isomers to those which are nearly circular with high aromatic conjugation lengths for a given aromatic ring count. These results stand in contrast to recent reports that suggest higher aliphatic composition of primary particles. [ABSTRACT FROM AUTHOR]

Surface assisted laser desorption ionization mass spectrometry (SALDI-MS) has been recognized as one of the prominent techniques in mass analysis of small molecules as well as large nonvolatile molecules since it bears many advantages compared to matrix assisted laser desorption ionization mass spectrometry. The use of SALDI-MS has been increasing for small molecules analysis with the development of new substrates materials for ionization such as porous silicons and nanomaterials. While most of researches about SALDI-MS are focusing on the development of new substrate materials, not much of works has been done for the verification of ionization mechanism of SALDI-MS. In this article, we reviewed the characteristics of SALDI-MS such as desorption/ionization mechanisms, signal enhancement by inorganic matrix, and recent trends on the development of new efficient matrix substrates. Among the reviewed ionization mechanisms, the laser ablation followed by generation of laser-induced plasma and shock wave is suggested to be more plausible mechanism in the desorption and ionization process of SALDI-MS, while other mechanisms are also recognized to contributes to the desorption and ionization process. Recent development of efficient substrate materials for SALDI-MS by adopting nanoparticles, nanomaterials, metal organic frameworks, and their combination was also reviewed. [ABSTRACT FROM AUTHOR]

We herein report the optimization and application of silver cationization (Ag+) in combination with laser desorption ionization (LDI) ultrahigh-resolution mass spectrometry (UHR-MS) to determine the structures of the sulfur-containing compounds present in heavy crude oil. A number of sulfur-containing model compounds were used to optimize the positive-ion mode LDI-MS conditions in the presence of a silver-complexing agent. Under the optimized LDI conditions, sulfur-rich heavy oil fractions were treated with the silver salt, where Ag+ coordinated with the sulfur atoms to speciate the sulfur species. The obtained results suggested that benzothiophenic, naphtheno-non-aromatic sulfides, and non-aromatic thiols were the major components present in the analyzed oil sample. [ABSTRACT FROM AUTHOR]

Laser desorption ionization mass spectrometry (LDI-MS) has been developed to be an essential tool for the analysis and identification of a large variety of species, ranging from small metabolites, drugs and pollutants to peptides and proteins and even to bacteria. Matrix assisted LDI-MS has shown a great power for macromolecules, but its analytical capability to low mass compounds is limited due to inherent drawbacks, including abundant interference in low mass range (<800 Da) caused by matrix self-dissociation and poor reproducibility due to inhomogeneous crystallization. Several matrix-free methods have been developed to solve these issues, mainly through altering organic matrix with inorganic nanostructured surfaces or nanomaterials as LDI medium. In the past five years, improvements on conventional silicon-based, metal-based, metal oxide-based and carbon-based LDI media as well as emerging novel materials such as 2D nanomaterials and organic frameworks have gained important progresses. Meanwhile, with the deep research in light-matter interaction, LDI mechanism studies begin to grow and become to attach great importance. Advances in both medium and mechanism promote to expand the applicable potential of nanostructure/nanomaterial-assisted LDI-MS in many aspects, including trace analysis, structural analysis and MS imaging. In this review, we survey the major progresses in this area in recent years. We also sketch remaining challenges and directions for future development. Image 1 • The latest advances on nanostructure/nanomaterial-assisted laser desorption ionization mass spectrometry (LDI-MS). • The LDI media contain two categories: nanostructured surfaces and nanomaterials. • Recent mechanism explanations on nanostructure/nanomaterial-assisted LDI-MS. • Comparison of current applications of nanostructure/nanomaterial-assisted LDI-MS. [ABSTRACT FROM AUTHOR]

This study compared Sb2Se3 material in the form of commercial polycrystalline bulk, sputtered thin film, and homemade polycrystalline material using laser desorption ionization (LDI) time of flight mass spectrometry with quadrupole ion trap mass spectrometry. It also analyzed the stoichiometry of the SbmSen clusters formed. The results showed that homemade Sb2Se3 bulk was more stable compared to thin film; its mass spectra showed the expected cluster formation. The use of materials for surface-assisted LDI (SALDI), i.e., graphene, graphene oxide, and C60, significantly increased the mass spectra intensity. In total, 19 SbmSen clusters were observed. Six novel, high-mass clusters—Sb4Se4+, Sb5Se3-6+, and Sb7Se4+—were observed for the first time when using paraffin as a protective agent. [ABSTRACT FROM AUTHOR]

Mass spectrometry imaging (MSI) is capable of detection and identification of diverse classes of compounds in brain tissue sections, whereas simultaneously mapping their spatial distributions. Given the vast array of chemical components present in neurological systems, as well as the innate diversity within molecular classes, MSI platforms capable of detecting a wide array of species are useful for achieving a more comprehensive understanding of their biological roles and significance. Currently, matrix‐assisted laser desorption ionization (MALDI) is the method of choice for the molecular imaging of brain samples by mass spectrometry. However, nanostructured laser desorption ionization platforms, such as silicon nanopost arrays (NAPA), are emerging as alternative MSI techniques that can provide complementary insight into molecular distributions in the central nervous system. In this work, the molecular coverage of mouse brain lipids afforded by NAPA‐MSI is compared to that of MALDI‐MSI using two common MALDI matrices. In positive ion mode, MALDI spectra were dominated by phosphatidylcholines and phosphatidic acids. NAPA favored the ionization of phosphatidylethanolamines and glycosylated ceramides, which were poorly detected in MALDI‐MSI. In negative ion mode, MALDI favored sulfatides and free fatty acids, whereas NAPA spectra were dominated by signal from phosphatidylethanolamines. The complementarity in lipid coverages between the NAPA‐ and MALDI‐MSI platforms presents the possibility of selective lipid analysis and imaging dependent upon which platform is used. Nanofabrication of the NAPA platform offers better uniformity compared to MALDI, and the wider dynamic range offered by NAPA promises improved quantitation in imaging. [ABSTRACT FROM AUTHOR]

We have developed laser desorption ionization mass spectrometry (LDI-MS) of organic molecules encapsulated in a crystalline sponge (CS). Cyclic organic compounds 1,2,3,4,5-pentamethylcyclopentadiene, zerumbone, and muscone were encapsulated in CS as guest regardless of guest crystallization. Single-crystal X-ray analysis closely scrutinized the position of the guest in the pore and the interaction between the guest and the CS framework. After single-crystal X-ray analysis, the same single crystal was subjected to LDI-MS. Ionization efficiency differed markedly depending on whether π−π interaction existed or not. It is obvious that π−π interaction is the key to transferring laser energy from the CS framework to the guest for the ionization of molecule encapsulated in CS. The results suggest the importance of controlling the positions of analyte and matrix as well as noncovalent interactions, such as hydrogen bonding interaction, electrostatic interaction, and so on. Image 1 • Crystalline sponge can encapsulate three different sized cyclic organic compounds. • Single crystal X-ray analyses revealed two encapsulation modes: via -attractive π-π interaction and via- dispersion force depending on the size and shape of the molecule. • In laser desorption ionization, ion peaks derived from the analyte were only detected in the presence of π-π interaction between the analyte and the CS frameworks. • Crystalline sponge laser desorption ionization is promising method to clarify the mechanism of laser desorption ionization using matrix. [ABSTRACT FROM AUTHOR]

The determination of the chemical characterization and the order of ink crossing by ballpoint pens have received increasing and important attention in forensic analysis due to forgery or alteration of documents strongly related to their use. The examination of these cases must be using non-destructive methods, in order to preserve the integrity of the evidence present in the documents. Laser desorption ionization mass spectrometry (LDI-MS) and LDI mass spectrometry imaging (LDI-MSI) have been widely applied in forensic document analysis by offering specific information on the chemical composition of the material from the mass to charge ratio (m / z) of the dyes without destroying the spatial location of the analytes. In this work, the combination of LDI data with statistical treatment, such as principal components analysis, classified the blue and black pen inks according to their 11 brands and 18 models studied. The interpretation of the LDI mass spectra allowed a chemical profile analysis relating the concept of relative ion intensity of the following dyes: methyl violet (m / z 372), ethyl violet (m / z 456), basic blue 26 (m / z 470), and basic blue 7 (m / z 478). In addition, the order of ink crossing (pen over pen, pen over printer and vice versa) was determined by monitoring the ions: methyl violet dye (m / z 372), their homologues (m / z 358, 344, 330, 316) and basic blue 7 (m / z 478) for the pens; and the ions of m / z 285 and 355, for inkjet and laserjet printers, respectively, by the LDI (+) MSI. Unlabelled Image • The chemical characterization of pens and the order of traces crossing is important in forensic analysis. • The examination of these cases must be using non-destructive methods. • LDI (+) MS and LDI (+) MS imaging have been widely applied in forensic document analysis. • The combination of LDI (+) MS with PCA classified the blue and black pen inks according to their brands. • The order of lines crossing using MS imaging was determined for pen over pen, and pen over printer. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work is to generate and study the clusters formed as a result of the interaction of laser pulses with solid state materials such as chalcogenide glasses. The other target is to determine the stoichiometry of the clusters generated from studied chalcogenide glasses and their thin films in order to get the information about structural fragments presents in the plasma plume. The aims were achieved by exploiting laser desorption ionization (LDI) with quadrupole ion trap time-of-flight mass spectrometry (TOFMS) examination of the Ge x Se 1- x (x = 0.1, 0.2, 0.3, 0.33) chalcogenide glasses and Ge 0.2 Se 0.8 and Ge 0.33 Se 0.67 thin films prepared by magnetron sputtering. The interaction of laser pulses with Ge x Se 1- x chalcogenide glasses and their thin films produces many positively and negatively charged unary and binary (Ge a +/−, Se b +/−, and Ge a Se b +/−) clusters. About ~50 different clusters were identified for each glass sample. We assume that some species indicate local structure of the studied materials. However, other clusters are formed either by a fragmentation of original glass structure or by laser ablation synthesis. When using parafilm, many new, higher mass clusters were produced. The results were compared with LDI TOFMS analysis of Ge:Se elemental mixtures. Concluding, LDI TOFMS is useful technique not only for the generation and study of the clusters but also it gives partial structural information about glasses and other materials as well as information about processes proceeding in the plasma. Highlights • Laser desorption ionization time-of-flight mass spectrometry of chalcogenides. • Ge x Se 1- x (x = 0.1, 0.2, 0.3, 0.33) chalcogenide glasses mass spectroscopy performed. • Ge-Se amorphous thin films, Ge:Se mixtures mass spectra presented. • 50 different clusters (Ge a +/−, Se b +/−, and Ge a Se b +/−) identified in mass spectra. [ABSTRACT FROM AUTHOR]

The binary system Sb-Se was studied via laser ablation using antimony-selenium mixtures made from powdered elements in various ratios generating new SbmSen clusters. The results show that in addition to Sbm+ (m = 1–8) and Sen+ (n = 2–9) clusters, a series of SbmSen+ clusters such as SbSe1–8+, Sb2Se1–6+, Sb3Se1–5+, Sb4Se1–3+, and Sb5Se1,2+ is generated. In addition, some low intensity oxidized clusters like Se6O2+, Se7O2+, and SbSe2-6O5+ and partially hydroxylated clusters (SbSeO2H7+, SbSe5O4H+) are also formed. In total, 24 new antimony selenide clusters were generated. The knowledge gained can contribute to the elucidation of the structure of SbmSen glasses. Graphical Abstract [ABSTRACT FROM AUTHOR]

Nanoparticles are efficient matrices in laser desorption/ionization (LDI) mass spectrometry (MS), especially for the profiling or imaging of small molecules. Recently, solvent-free physical vapor desorption (PVD), or sputter coating, was adopted as a homogenous method to rapidly apply metal nanoparticles (NPs) in situ to samples prior to LDI MS or MS imaging analysis. However, there has been no systematic study comparing different metal targets for the analysis of a variety of small molecule metabolites. Here, we present a screening and optimization of various sputter-coated metals, including Ag, Au, Cu, Pt, Ni, and Ti, for LDI analysis of small molecules in both positive and negative ion modes. Optimized sputter coating is then applied to high-spatial resolution LDI mass spectrometry imaging (MSI) of maize root and seed cross-sections. Noble metals, Ag, Au, and Pt, are found to be much more efficient than transition metals and organic matrices for most small metabolites. Sputter-coated metals are efficient for neutral lipids, such as triacylglycerols and diacylglycerols, but are very inefficient for most phospholipids.ᅟ [ABSTRACT FROM AUTHOR]

The variation among individual cells plays a significant role in many biological functions. Single-cell analysis is advantageous for gaining insight into intricate biochemical mechanisms rarely accessible when studying tissues as a whole. However, measurement on a unicellular scale is still challenging due to unicellular complex composition, minute substance quantities, and considerable differences in compound concentrations. Mass spectrometry has recently gained extensive attention in unicellular analytical fields due to its exceptional sensitivity, throughput, and compound identification abilities. At present, single-cell mass spectrometry primarily concentrates on the enhancement of ionization methods. The principal ionization approaches encompass nanoelectrospray ionization (nano-ESI), laser desorption ionization (LDI), secondary ion mass spectrometry (SIMS), and inductively coupled plasma (ICP). This article summarizes the most recent advancements in ionization techniques and explores their potential directions within the field of single-cell mass spectrometry., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zeng, Xia, Yin, Cheng, Xue, Tan, Gong and Ye.)

Metal oxide cluster ions, M n O m ± (M = Zn, Cd) and Hg n O m − of various stoichiometry have been generated from solid IIB-VIA semiconductor oxides targets, (ZnO (s) , CdO (s) , and HgO (s) ) by using pulse laser desorption ionization time of flight mass spectrometry with a laser of λ = 355 nm. Analysis of mass spectral data indicates the formation of stoichiometric cluster ions viz., (ZnO) n=1-30 + and (CdO) n=1-40 + along with –O bound anions, (ZnO) n=1-30 O − , (CdO) n=1-40 O − and (HgO) n=1-36 O − from their respective solids. Further, metal oxoanions such as ZnO n=2,3 − , CdO n=2,3,6 − , and HgO n=2,3,6,7 − have also been noted signifying the higher coordination ability of both Cd and Hg with O/O 2 /O 3 species. [ABSTRACT FROM AUTHOR]

It has been known for about sixty years that proton and heavy ion therapy is a very powerful radiation procedure for treating tumors. It has an innate ability to irradiate tumors with greater doses and spatial selectivity compared with electron and photon therapy and, hence, is a tissue sparing procedure. For more than twenty years, powerful lasers have generated high energy beams of protons and heavy ions and it has, therefore, frequently been speculated that lasers could be used as an alternative to radiofrequency (RF) accelerators to produce the particle beams necessary for cancer therapy. The present paper reviews the progress made towards laser driven hadron cancer therapy and what has still to be accomplished to realize its inherent enormous potential.

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study AsCh (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S and As ) and 34 binary (AsS ) species for AsS glass, 2 unary (Se ) and 26 binary (AsSe ) species for AsSe glass, 7 unary (Te ) and 23 binary (AsTe ) species for AsTe material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials. [ABSTRACT FROM AUTHOR]

In this report the successful generation of the non-isolated pentagon rule (non-IPR) fullerene fragment via regioselective cyclodehydrofluorination of a specially designed precursor under laser ionization condition is presented. It is demonstrated that the transformation of the precursor molecule to the highly strained non-IPR bowl-shaped hydrocarbon can be achieved effectively at rather low laser fluences, despite the presence of fused pentagons in the structure. This finding opens up a venue towards the rational synthesis of individual isomers of non-IPR fullerenes and other related non-IPR architectures by the bottom-up strategy. The retrosynthetic analysis of fluoroarene-based precursor molecules for non-IPR fullerenes C36-C50 is discussed. [ABSTRACT FROM AUTHOR]

The degradation of hole transport materials has been studied via laser desorption ionization-time of flight (LDI-TOF) of aged and unaged OLED devices, TOF/TOF of cations, and DFT calculation of bond dissociation energies. We were able to show that TAPC, one of the archetypical hole-transport materials, undergoes cation induced cyclohexyl ring-opening reaction with device operation. This alternative degradation pathway is in addition to C N bond dissociation commonly observed in polycyclic aromatic amines. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (NP) with average diameter ~100 nm synthesized from tetrachloroauric acid solution using stainless steel as a reducing agent were found to contain iron. Applying simultaneously high frequency (HF) plasma discharge in solution during the electrochemical reduction, giant gold-iron nanoflowers with average size ~1000-5000 nm were formed. Scanning electron microscopy (SEM) shows the morphology of the nanopowders produced as polygonal yet nearly spherical, whereas iron content in both products determined by energy dispersive X-ray analysis (EDX) was found to be at ~2.5 at. %. Laser desorption ionization (LDI) of both nanomaterials and mass spectrometric analysis show the formation of AuFe ( m = 1-35; n = 1-3) clusters. Structure of few selected clusters in neutral or monocharged forms were computed by density functional theory (DFT) calculations and it was found that typical distances of an iron nucleus from adjacent gold nuclei lie in the interval 2.5 to 2.7 Å. Synthetized Au-Fe nanoparticles were found stable for at least 2 mo at room temperature (even in aqueous solution) without any stabilizing agent. Produced Au-Fe nanoparticles in combination with standard MALDI matrices enhance ionization of peptides and might find use in nanomedicine. [ABSTRACT FROM AUTHOR]

Mercury fluoride ions formed during the laser ablation of HgF 2(s) show the formation of six different cluster ion series viz., HgF n ± , Hg n F n-2 ± , Hg n F n-1 ± , (HgF) n ± , Hg n F n+1 ± , and Hg n F n+2 ± . Among the different ion series, the observation of high valent HgF n ± (n ± =3,4; n - =6-8) indicates the existence of corresponding molecules which signify the remarkable participation of 5d Hg electrons in the chemical bonding with F atoms and thus make Hg a truly transition metal. Further, molecular orbital calculations show a large HOMO-LUMO energy gap (≥3 eV) and high electron affinity (≥5 eV) that indicates highly stable HgF n=3,4,6,8 with super halogen properties., (© 2023 Wiley-VCH GmbH.)

[Display omitted] • Sputter-deposited metals can be used as matrix for laser desorption ionization mass spectrometry. • Metal-assisted laser desorption ionization imaging mass spectrometry can be used to analyze and map the molecular content of thin tissue sections and fingermarks. • High specificity and sensitivity can be obtained for cholesterol and fatty acids by silver-assisted laser desorption ionization imaging mass spectrometry. • High specificity and sensitivity can be obtained for triglycerides by gold-assisted laser desorption ionization imaging mass spectrometry. Traditionally, matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) requires the homogenous deposition of an organic matrix prior to analysis. However, organic matrices often generate high background noise in the low mass range (below ∼800 Da) that often prevents the detection and identification of lower molecular weight compounds, especially if these are present in low abundance. Laser desorption ionization (LDI) allows for selective ionization of targeted species with very low background in the low mass range. In this article, the advantages and disadvantages of both solvent free and wet deposition of metals as LDI matrices developed in our laboratory are presented and discussed in the context of IMS analyses. Through several original examples, we highlight the power of silver and gold-based metal-assisted LDI to analyze selected low molecular weight molecules from tissue sections by IMS, including intact cholesterol, triacylglycerols, fatty acids, and phospholipids, as well as numerous other endogenous substances embedded within fingermarks. [ABSTRACT FROM AUTHOR]

Single particle aerosol mass spectrometry (SPAMS), an analytical technique for measuring the size and composition of individual micron-scale particles, is capable of analyzing atmospheric pollutants and bioaerosols much more efficiently and with more detail than conventional methods which require the collection of particles onto filters for analysis in the laboratory. Despite SPAMS' demonstrated capabilities, the primary mechanisms of ionization are not fully understood, which creates challenges in optimizing and interpreting SPAMS signals. In this paper, we present a well-stirred reactor model for the reactions involved with the laser-induced vaporization and ionization of an individual particle. The SPAMS conditions modeled in this paper include a 248 nm laser which is pulsed for 8 ns to vaporize and ionize each particle in vacuum. The ionization of 1 μm, spherical Al particles was studied by approximating them with a 0-dimensional plasma chemistry model. The primary mechanism of absorption of the 248 nm photons was pressure-broadened direct photoexcitation to Al(y2D). Atoms in this highly excited state then undergo superelastic collisions with electrons, heating the electrons and populating the lower energy excited states. We found that the primary ionization mechanism is electron impact ionization of various excited state Al atoms, especially Al(y2D). Because the gas expands rapidly into vacuum, its temperature decreases rapidly. The rate of three-body recombination (e− + e− + Al+ → Al + e−) increases at low temperature, and most of the electrons and ions produced recombine within several μs of the laser pulse. The importance of the direct photoexcitation indicates that the relative peak heights of different elements in SPAMS mass spectra may be sensitive to the available photoexcitation transitions. The effects of laser intensity, particle diameter, and expansion dynamics are also discussed. [Display omitted] • Ionization mechanisms in single particle aerosol mass spectrometers are studied. • A 0-dimensional model quantifies various processes for Al particles. • Pressure broadening enables direct photoexcitation. • Electron impact ionization of excited states is the primary ionization mechanism. • Most of the electrons and ions recombine within several microseconds. [ABSTRACT FROM AUTHOR]

A new atmospheric pressure ionization method termed pyroelectricity-assisted infrared laser desorption ionization (PAI-LDI) was developed in this study. The pyroelectric material served as both sample target plate and enhancing ionization substrate, and an IR laser with wavelength of 1064 nm was employed to realize direct desorption and ionization of the analytes. The mass spectra of various compounds obtained on pyroelectric material were compared with those of other substrates. For the five standard substances tested in this work, LiNbO substrate produced the highest ion yield and the signal intensity was about 10 times higher than that when copper was used as substrate. For 1-adamantylamine, as low as 20 pg (132.2 fmol) was successfully detected. The active ingredient in (Compound Paracetamol and 1-Adamantylamine Hydrochloride Capsules), 1-adamantylamine, can be sensitively detected at an amount as low as 150 pg, when the medicine stock solution was diluted with urine. Monosaccharide and oligosaccharides in Allium Cepa L. juice was also successfully identified with PAI-LDI. The method did not require matrix-assisted external high voltage or other extra facility-assisted set-ups for desorption/ionization. This study suggested exciting application prospect of pyroelectric materials in matrix- and electricity-free atmospheric pressure mass spectrometry research. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new and rapid approach for analysis of olive oil has been developed using sorptive tape-like extraction in combination with laser desorption ionization mass spectrometry (STELDI-MS). This powerful combination has some great advantages, as no-separation steps, solvent-free, matrix-free, and no sample preparation. The olive oil compounds are analyzed by LDI-MS, directly from the sample spot in a thin-layer chromatography (TLC) plate. Chosen samples represent products commonly used as adulterants in extra virgin olive oil (EVOO) and the main monitored ions were lipid adulteration markers. Analytical procedures consisted of profiling the main fatty acids ( m / z 255 – palmitic acid, 279 – linoleic acid, 281 – oleic acid and 283 – stearic acid), triacylglycerols ( m / z 901 – LLL and 907 – OOO) and some phenolic compounds ( m / z 169 – gallic acid, 193 – ferulic acid and 195 – 2(4-hydroxyphenyl) ethyl acetate) in extra virgin olive oil (EVOO), olive oil (OO), hazelnut oil (HO) and soybean oil (SO). Compound identification was confirmed by analysis of collision-induced dissociation (CID) products in positive (ion [M+Na] + ) and negative mode (ion [M−H] − ). This method is simple, fast and efficient in identifying compounds that can be used to recognize different levels of adulteration, oxidation and hydrolysis of vegetables oils. [ABSTRACT FROM AUTHOR]

Here we present a proof of concept cross-platform normalization approach to convert raw mass spectra acquired by distinct desorption ionization methods and/or instrumental setups to cross-platform normalized analyte profiles. The initial step of the workflow is database driven peak annotation followed by summarization of peak intensities of different ions from the same molecule. The resulting compound-intensity spectra are adjusted to a method-independent intensity scale by using predetermined, compound-specific normalization factors. The method is based on the assumption that distinct MS-based platforms capture a similar set of chemical species in a biological sample, though these species may exhibit platform-specific molecular ion intensity distribution patterns. The method was validated on two sample sets of (1) porcine tissue analyzed by laser desorption ionization (LDI), desorption electrospray ionization (DESI), and rapid evaporative ionization mass spectrometric (REIMS) in combination with Fourier transformation-based mass spectrometry; and (2) healthy/cancerous colorectal tissue analyzed by DESI and REIMS with the latter being combined with time-of-flight mass spectrometry. We demonstrate the capacity of our method to reduce MS-platform specific variation resulting in (1) high inter-platform concordance coefficients of analyte intensities; (2) clear principal component based clustering of analyte profiles according to histological tissue types, irrespective of the used desorption ionization technique or mass spectrometer; and (3) accurate 'blind' classification of histologic tissue types using cross-platform normalized analyte profiles. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Anisotropy at the nanoscale fascinates researchers in various areas of science and technology. Well-known applications of anisotropic nanoparticles include biosensors and catalysis. However, utilization of gold nanostars in analytical chemistry is limited to surface enhanced Raman spectroscopy. LDI-MS assisted with gold nanostars has not been addressed for low molecular weight compounds. Herein, we report LDI-MS performance of phospholipids at nanomolar concentrations with application of gold nanostars for the first time. Intense signals of molecular ions were detected as metal adduct ions with relatively low fragmentation and signals of interferences in low-mass region. Nanostars were characterized with utilization of electron microscopic, X-Ray powder diffraction and dynamic light scattering techniques. The results showed that gold nanostars can serve as a bright perspective for new inorganic matrices in LDI-MS of low molecular weight compounds. [Display omitted] • LDI-MS performance of gold nanostars was reported for the first time. • Gold nanostars as inorganic matrix allowed registration of phospholipids at nanomolar level. • The study shows a bright perspective for future utilization of gold nanostars in LDI-MS. [ABSTRACT FROM AUTHOR]

Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and used in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single submillimeter-sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional liquid chromatography/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-μm resolution (∼4-y temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the ∼200-y de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and environmental factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments. [ABSTRACT FROM AUTHOR]

It has been known for about sixty years that proton and heavy ion therapy is a very powerful radiation procedure for treating tumors. It has an innate ability to irradiate tumors with greater doses and spatial selectivity compared with electron and photon therapy and, hence, is a tissue sparing procedure. For more than twenty years, powerful lasers have generated high energy beams of protons and heavy ions and it has, therefore, frequently been speculated that lasers could be used as an alternative to radiofrequency (RF) accelerators to produce the particle beams necessary for cancer therapy. The present paper reviews the progress made towards laser driven hadron cancer therapy and what has still to be accomplished to realize its inherent enormous potential. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fullerene films are excited with infrared lasers and ions (positive and negative) are detected with time-of-flight mass spectrometry. [•] The mechanism of infrared desorption and ionization is investigated with different samples and IR wavelengths. [•] Tunable IR studies provide desorbed ion infrared spectra of C60, revealing new vibrational combination bands. [Copyright &y& Elsevier]

The structural effect of a nanoporous gold (NPG) surface on the signal intensities of laser desorption ionization-mass spectrometry (LDI-MS) were investigated using NPG surfaces with controlled structures. The relationship between surface area and LDI efficiency was compared and evaluated. Comparisons between bare flat gold and NPG surfaces show that nanostructures increased LDI efficiency. We also found that the LDI signal decreased with increasing depth of nanoporous layers, thus increasing the surface area. This result agrees with a previous report (Shin J. A. et al., J. Am. Soc. Mass Spectrom. 2010, 21, 989) in which the LDI efficiency of small molecules decreased for ZnO wires with longer lengths. This observation was explained by the penetration and deposition of samples into locations inaccessible to photons because of structural screening. The LDI-MS analysis of oils with NPG surfaces (but without matrix) showed the same trend whereby the NPG with about a 200 nm depth of porous area showed the highest sensitivity. This study clearly shows that the active surface area for solution chemistry can differ from LDI-MS and that NPGs can function as a substrate for LDI oil analysis. [ABSTRACT FROM AUTHOR]

Nanomaterials have emerging importance in laser desorption ionization mass spectrometry (LDI-MS) with the ultimate objective being to overcome some of the most important limitations intrinsically related to the use of conventional organic matrices in matrix-assisted (MA) LDI-MS. This review provides a critical overview of the most recent literature on the use of gold nanomaterials as non-conventional desorption ionization promoters in LDI-MS, with particular emphasis on bioanalytical applications. Old seminal papers will also be discussed to provide a timeline of the most significant achievements in the field. Future prospects and research needs are also briefly discussed. [ABSTRACT FROM AUTHOR]