Laser ablation synthesis of new gold phosphides using red phosphorus and nanogold as precursors. Laser desorption ionisation time-of-flight mass spectrometry

Geometrical Structures and Dissociation Channels of CuP2n + (n = 2-11): Studied by Mass Spectrometry and Theoretical Calculations

Transition metal phosphorus cluster cations CuP_2n ⁺ (2 ≤ n ≤ 11) were studied by laser ablation mass spectrometry and collision-induced dissociation (CID). The magic-numbered cluster ion of CuP₈ ⁺ was identified experimentally, and cluster ions of CuP₁₄ ⁺ and CuP₁₈ ⁺ were also found to be generated with high abundance. CID results show that the dissociation channels of CuP_2n ⁺ (n = 4 and 6-10) are all characterized by the loss of the P₄ unit. Theoretical calculations combining global minima searching with the basin-hopping method and density functional theory (DFT) optimizations were performed for these clusters. Among them, the magic-numbered cluster CuP₈ ⁺ was characterized by a D_2d symmetry, with the Cu atom bridging two P₄ units. The most stable isomer of CuP₁₄ ⁺ was found to be characterized by a C_2v symmetry. Calculations also reflect that the dissociation channels of the loss of the P₄ unit are more energetically favorable than those of the loss of the P₂ unit for CuP_2n ⁺ (n = 4 and 6-10), which are in good consistent with the experimental results.

Detection of serum phospholipids by microchannel-integrated black phosphorus-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been widely applied in the analysis of phospholipids in biological samples. However, it remains a challenge to improve the sensitivity and reproducibility and to control the background noise of matrices. In this study, black phosphorus nanomaterial was used as the matrix of MALDI-MS, and microchannel technique was combined. This microchannel-integrated black phosphorus-assisted laser desorption/ionization (BPALDI) MS approach can effectively detect a variety of lipids with a small amount of sample, and has high sensitivity for phosphatidylcholines (PC) and lysophosphatidylcholines (LPC) with a detection limit of 0.2 μg/mL. Compared with traditional matrices, BPALDI-MS has the advantages of high sensitivity, good reproducibility, and high salt tolerance. This method was successfully applied in the detection of serum PC/LPC ratios in children patients with asthma or bronchopneumonia. This work provides a novel application of black phosphorus matrix and microchannel technique, and gives new insights into method development of rapid screening and identification of disease indicators in biological fluids.

Laser ablation synthesis of carbon-phosphides from graphene/nanodiamond-phosphorus composite precursors: Laser desorption ionisation time-of-flight mass spectrometry

RATIONALE

Carbon-phosphides are new and promising strategic materials with applications e.g. in optoelectronics. However, their chemistry and methods of synthesis are not completely understood, and only a limited number of C-P clusters have been detected up to now. Laser ablation synthesis (LAS) or laser desorption ionisation (LDI) has great potential to generate C_m P_n clusters in the gas phase and to act as the basis for the development of new technology.

METHODS

The LAS of carbon phosphides using mixtures of nano-carbon sources (graphene, nanodiamonds) with phosphorus allotropes (red, black, and phosphorene) was examined. Since phosphorene is not commercially available, it was synthesised. A reflectron time-of-flight mass spectrometer was used to produce and identify the C-P clusters. A transmission electron microscope was used to characterise the prepared composites.

RESULTS

LDI of various carbon-phosphorus composites generated a range of carbon-phosphides. From graphene-red phosphorus, C_m P⁺ (m = 3-47), C_m P₂ ⁺ (m = 2-44), C_m P₃ ⁺ (m = 1-42), C_m P₄ ⁺ (m = 1-39), C_m P₅ ⁺ (m = 1-37), C_m P₆ ⁺ (m = 1-34), C_m P₇ ⁺ (m = 1-31), C_m P₈ ⁺ (m = 1-29), C_m P₉ ⁺ (m = 1-26), C_m P₁₀ ⁺ (m = 1-24), C_m P₁₁ ⁺ (m = 1-21), and C_m P₁₂ ⁺ (m = 1-19) clusters were detected, while nanodiamond composites with red/black phosphorus and with phosphorene yielded C₂₄ P_5 + 2n ⁺ (n = 0-28), C₂₄ P_5 + 2n ⁺ (n = 0-16), and C₂₄ P_5 + 2n ⁺ (n = 0-14) clusters, respectively. In total, over 300 new carbon-phosphide clusters were generated.

CONCLUSIONS

The novel series of carbon-phosphide clusters generated from graphene or nanodiamond composites with red/black phosphorus or with phosphorene demonstrated rich carbon-phosphide chemistry that might inspire the development of novel nano-materials with specific properties.

Clusters of Monoisotopic Elements for Calibration in (TOF) Mass Spectrometry

Precise calibration in TOF MS requires suitable and reliable standards, which are not always available for high masses. We evaluated inorganic clusters of the monoisotopic elements gold and phosphorus (Au _n⁺/Au _n^- and P _n⁺/P _n^-) as an alternative to peptides or proteins for the external and internal calibration of mass spectra in various experimental and instrumental scenarios. Monoisotopic gold or phosphorus clusters can be easily generated in situ from suitable precursors by laser desorption/ionization (LDI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Their use offers numerous advantages, including simplicity of preparation, biological inertness, and exact mass determination even at lower mass resolution. We used citrate-stabilized gold nanoparticles to generate gold calibration clusters, and red phosphorus powder to generate phosphorus clusters. Both elements can be added to samples to perform internal calibration up to mass-to-charge (m/z) 10-15,000 without significantly interfering with the analyte. We demonstrated the use of the gold and phosphorous clusters in the MS analysis of complex biological samples, including microbial standards and total extracts of mouse embryonic fibroblasts. We believe that clusters of monoisotopic elements could be used as generally applicable calibrants for complex biological samples. Graphical Abstract ᅟ.

Structural elucidation of AgAsS2 glass by the analysis of clusters formed during laser desorption ionisation applying quadrupole ion trap time-of-flight mass spectrometry

RATIONALE

The structure of AgA(s)S2 glass, which has a broad range of applications, is still not well understood and a systematic mass spectrometric analysis of AgA(s)S2 glass is currently not available. Elucidation of the structure should help in the development of this material.

METHODS

The AgA(s)S2 glass was prepared by the melt-quenched technique. Laser desorption ionisation (LDI) using quadrupole ion trap time-of-flight mass spectrometry (QIT-TOFMS) was used to follow the generation of Ag(m)As(n)S(x) clusters. The stoichiometry of the clusters generated was determined via collision-induced dissociation (CID) and modelling of isotopic patterns. The AgA(s)S2 glass was characterised by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy.

RESULTS

The LDI of AgA(s)S2 glass leads to the formation of unary (Ag+/− and As(3+)) species, 38 binary (As(n)S(x), Ag(m)S(x)), and 98 ternary (Ag(m)As(n)S(x)) singly charged clusters. The formation of silver-rich nano-grains during AgA(s)S2 glass synthesis has been identified using TEM analysis and also verified by QIT-TOFMS.

CONCLUSIONS

TOFMS was shown to be a useful technique to study the generation of Ag(m)As(n)S(x )clusters. SEM, TEM and EDX analysis proved that the structure of AgA(s)S2 glass is ‘grain-like’ where grains are either: (1) Silver-rich ‘islands’ (Ag(m,) m up to 39) connected by arsenic and/or sulfur or arsenic sulfide chains or (2) silver sulfide (Ag2S)m (m = 9-20) clusters also similarly inter-connected. This obtained structural information may be useful for the development of ultra-high-density phase-change storage and memory devices using this kind of glass as a base.

Electronic properties of red and black phosphorous and their potential application as photocatalysts

The promising potential of monolayerrPandbPas photocatalysts was identified, due to their suitable band gap, appropriate band edge position, higher mobility and separation efficiency of charge carriers, and strong response to visible light.

Theoretical studies on the bonding and electron structures of a [Au3Sb6]3− complex and its oligomers

Theoretical studies of an all-metal [Sb₃Au₃Sb₃]³⁻ sandwich complex and its congeners [X₃M₃X₃]³⁻ (M = Cu, Ag, Au, Rg; X = N, P, As, Sb, Bi, Uup) as well as [Sb₃(Au₃Sb₃)_n]³⁻ (n = 1–4) oligomers indicate the possible existence of other [A_pM_pA_p]^x− sandwich compounds and oligomers.

Use of flower-like gold nanoparticles in time-of-flight mass spectrometry

RATIONALE

Many kinds of nanoparticles (NPs) have been used for mass spectrometry (MS) so far. Here we report the first use of flower-like gold nanoparticles (AuNPs) as a mediator to enhance ionization in MS of peptides and proteins.

METHODS

Flower-like AuNPs were characterized using transmission and scanning electron microscopy, UV-VIS spectrophotometry, and laser desorption/ionization (LDI)-MS and compared with polyhedral AuNPs. Mass spectra were obtained in positive ion mode using a time-of-flight (TOF) analyzer coupled with either matrix-assisted laser desorption/ionization (MALDI) or surface-assisted laser desorption/ionization (SALDI) methods.

RESULTS

The intensities of peptide peaks (m/z 500-3500) were up to 7.5× and up to 7× higher using flower-like AuNPs and flower-like AuNPs-enriched α-cyano-4-hydroxycinnamic acid (CHCA) matrix respectively, than the classical CHCA matrix. The signals of higher mass peptide/protein peaks (m/z 3600-17000) were up to 2× higher with using flower-like AuNPs-enriched CHCA matrix than conventional CHCA matrix. The signal of profile peaks generated by intact cell MALDI-TOFMS of fibroblast suspension (m/z 4000-20000) was 2× higher with using flower-like AuNPs combined with sinapinic acid (SA) compared to SA matrix alone. The use of flower-like AuNPs as internal calibration standard for the calibration of MS spectra of peptides was performed.

CONCLUSIONS

Flower-like AuNPs and flower-like AuNPs combined with CHCA or SA as combined matrices for MS measurement of peptides and proteins were used. Comparison of the conventional MALDI method and our method with flower-like AuNPs was carried out. In addition, gold clusters generated from flower-like AuNPs by SALDI provide a suitable internal calibration standard for MS analysis of peptides. Copyright © 2015 John Wiley & Sons, Ltd.

Laser ablation generation of clusters from As-Te mixtures, As-Te glass nano-layers and from Au-As-Te nano-composites. Quadrupole ion trap time-of-flight mass spectrometry

RATIONALE

Arsenic tellurides have found important applications in various fields of science, but only a few gold-arsenic tellurides have been reported. Laser ablation synthesis (LAS), a suitable method for the generation of new compounds, has been used to generate clusters from As-Te mixtures, an As-Te glass and Au-As-Te nano-composites.

METHODS

Chalcogenide glass nano-layers prepared via Physical Vapour Deposition - thermal evaporation were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). LAS with laser desorption ionisation quadrupole ion trap time-of-flight mass spectrometry (LDI QIT TOFMS) was used for the generation and analysis of new AuxAsmTen clusters. The stoichiometry of the clusters was determined via isotopic envelope modelling.

RESULTS

A simple procedure for the preparation of the Au-As-Te nano-composite was developed. From As-Te mixtures only five binary AsmTen clusters were generated, while from a glass layer 10 binary AsmTen clusters were identified, because during the deposition of the glass the elements reacted with each other to form a complex three-dimensional (3D) structure. Using LAS on the Au-As-Te nano-composite leads to the formation of six unary Ten (n = 1-6), 16 binary (AsmTen and AuxTen), and 31 ternary AuxAsmTen clusters.

CONCLUSIONS

LAS was demonstrated to be a useful technique for the generation of AuxAsmTen clusters in the gas phase. More AsmTen clusters were generated from the deposited glass layers than from As-Te mixtures. Most of the ternary AuxAsmTen clusters generated from the nano-composite are reported here for the first time.

On the properties of Au2P3z(z = −1, 0, +1): analysis of geometry, interaction, and electron density

Au₂P₃has been discovered to exhibit remarkable semiconductor properties among metal phosphides. A theoretical study focusing on the electron and interatomic interactions of Au₂P₃is performed and provides new insights for the synthesis of new materials.

Generation of new Agm Ten clusters via laser ablation synthesis using Ag-Te nano-composite as precursor. Quadrupole ion trap time-of-flight mass spectrometry

RATIONALE

Silver tellurides find applications in the development of infrared detection, imaging, magnetics, sensors, memory devices, and optic materials. However, only a limited number of silver tellurides have been described to date. Laser ablation synthesis (LAS) was selected to generate new Ag-Te clusters.

METHODS

Isothermal adsorption was used to study the formation of silver nano-particles-tellurium aggregates. Laser desorption ionization quadrupole ion trap time-of-flight mass spectrometry (LDI-QIT-TOFMS) was used for the generation and analysis of Agm Ten clusters. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to visualize the structure of materials. The stoichiometry of the generated clusters was determined by computer modeling of isotopic patterns.

RESULTS

A simple, one-pot method for the preparation of Ag-Te nano-composite was developed and found suitable for LAS of silver tellurides. The LDI of Ag-Te nano-composite leads to the formation of 11 unary and 52 binary clusters. The stoichiometry of the 34 novel Agm Ten clusters is reported here for the first time.

CONCLUSIONS

LAS with TOFMS detection was proven to be a powerful technique for the generation of silver telluride clusters. Knowledge of the stoichiometry of the generated clusters might facilitate the further development of novel high-tech silver tellurium nano-materials.

Generation of Au(p)Ag(q)Te(r) clusters via laser ablation synthesis using Au-Ag-Te nano-composite as precursor: quadrupole ion-trap time-of-flight mass spectrometry

RATIONALE

Metal tellurides have applications in various fields of science and technology but only a few gold-silver tellurides have been reported. The laser ablation synthesis (LAS) method allows the preparation of nano-materials from solid substrates. Therefore, this method was selected to synthesise some gold-silver tellurides.

METHODS

Laser desorption ionisation quadrupole ion trap time-of-flight mass spectrometry (LDI QIT TOF MS) was used for the generation of new Au(p)Ag(q)Te(r) clusters. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to characterise the materials. The stoichiometry of the clusters generated was determined via collision-induced dissociation (CID) and modeling of isotopic patterns.

RESULTS

Chemisorption of gold and silver nano-particles on tellurium powder led to the formation of a new kind of Au-Ag-Te nano-composite. The LDI of this nano-composite yielded nine unary (Ag(q), Te(r)), 40 binary (Au(p)Te(r) and Ag(p)Te(r)) and 78 ternary clusters. The stoichiometry of these novel Au(p)Ag(q)Te(r) clusters is reported here for the first time.

CONCLUSIONS

The new Au-Ag-Te nano-composite was found to be a more suitable precursor for the generation of clusters than the mixtures of the elements. TOF MS was shown to be a useful technique for following the generation of gold-silver tellurides. Knowledge of the cluster stoichiometry could accelerate the further development of novel high-tech materials such as chalcogenide glasses.

Laser ablation synthesis of new gold arsenides using nano-gold and arsenic as precursors. Laser desorption ionisation time-of-flight mass spectrometry and spectrophotometry

RATIONALE

Currently, a limited number of gold arsenides have been described, some of which have important industrial applications, Laser ablation synthesis (LAS) has been employed in an attempt to generate some novel gold arsenide compounds.

METHODS

LAS of gold arsenides was performed using nano-gold (NG) and arsenic as precursors. The clusters formed during laser desorption ionisation (LDI) were analysed by mass spectrometry using a quadrupole ion trap and reflectron time-of-flight analyser to determine the stoichiometry. UV/VIS spectrophotometry was used to follow possible hydrothermal synthesis of gold arsenides.

RESULTS

LAS of NG yielded singly charged gold clusters Aum (+(-)) (m = 1-35). LAS of bulk arsenic and nano-arsenic produced Asn (+(-)) clusters with n = 2-10 and n = 2-20, respectively. Laser ablation of Au-As nano-composites or NG-As mixtures generated Aum (+(-)) (m = 1-12), Asn (+(-)) (n = 3-4), and several series of Aum Asn (+(-)) (m = 1-60, n = 1-18) clusters. Over 450 species of gold arsenide clusters and 212 mixed chlorinated Aum Asn Clx clusters were detected and their stoichiometry determined.

CONCLUSIONS

Many new gold arsenides were synthesised via LAS for the first time with Au-As composites and NG-As mixtures of different Au:As ratios using mass spectrometry to determine cluster stoichiometry. The resolved stoichiometry of Aum Asn clusters determined in this study could accelerate the development of advanced Au-As nano-materials.

Laser ablation synthesis of new gold carbides. From gold-diamond nano-composite as a precursor to gold-doped diamonds. Time-of-flight mass spectrometric study

RATIONALE

Gold carbides can be produced via laser ablation synthesis (LAS) from mixtures of nano-gold (NG) and various carbonaceous materials. The nano-composite of nano-gold (NG) and nano-diamond (ND) might represent a promising precursor for the generation of new gold carbides.

METHODS

Time-of-flight mass spectrometry (TOF MS), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) were used. The stoichiometry of clusters was determined via modelling of the isotopic patterns and MS(n) analysis.

RESULTS

A simple procedure for the preparation of ND-NG nano-composite was developed using NG and ND. The formation of AuCn(+) (n = 1-11, 18), Au2Cn(+) (n = 1-16) and Au3Cn(+) (n = 1-10) clusters during LAS of the nano-composite was proved. Structures of gold carbides are proposed and discussed. Diamonds-containing AumCn(+) (m = 1-3, n = 10, 14, 18, 22) clusters might be not carbides but endohedral supramolecular complexes Aum@Cn(+) i.e., 'gold-doped' diamonds.

CONCLUSIONS

TOF MS was shown to be a useful technique for following the formation of gold carbides in the gas phase. Clusters and 'gold-doped' diamonds generated might inspire synthesis of new Au-C materials with hardly predictable, unusual properties.

Laser ablation synthesis of new gold tellurides using tellurium and nanogold as precursors. Laser desorption ionisation time-of-flight mass spectrometry

RATIONALE

Only a few gold tellurides are known. However, Laser Ablation Synthesis (LAS) using Laser Desorption Ionisation (LDI) time-of-flight mass spectrometry (TOF MS) has high potential for the generation of new compounds.

METHODS

LDI of nanogold-Te conjugate using a nitrogen laser 337 nm was applied while the mass spectra were recorded in positive and negative ion modes using a quadrupole ion trap-TOF mass spectrometer equipped with a reflectron. Diffuse coplanar surface barrier discharge was applied for the plasma treatment of glass and silicon surfaces.

RESULTS

A form of nanogold-Te conjugate was prepared and found suitable for LAS of gold tellurides. Several new Au(m)Te(n) (m = 1-11; n = 1-4) clusters were identified. An excess of nanogold and chloride or an excess of auric acid caused the formation of mixed Au(m)Te(n)Cl(x) clusters. The nanogold-Te conjugate can be deposited from an aqueous suspension onto glass while the deposition is strongly enhanced if the surface is modified by plasma.

CONCLUSIONS

LDI of nanogold-Te conjugate is a suitable procedure for the generation of new gold telluride clusters. Treatment of borosilicate glass with a diffuse coplanar surface barrier discharge strongly enhances the deposition of gold tellurides on glass while limited adsorption on a silicon surface was observed.