Photoluminescence with Peaked Structure: Inherent to Nanoparticles or Resulting From Impurities in Sample Vial Caps?

We show that fluorescence emission in the visible spectral range reported in the case of many nanoparticles, polymers, complexes and liquid crystals with molecular type signatures could originate from the organic impurities leaching from the caps of glass vials.     

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

Gold phosphides show unique optical or semiconductor properties and there are extensive high technology applications, e.g. in laser diodes, etc. In spite of the various AuP structures known, the search for new materials is wide. Laser ablation synthesis is a promising screening and synthetic method. Generation of gold phosphides via laser ablation of red phosphorus and nanogold mixtures was studied using laser desorption ionisation time‐of‐flight mass spectrometry (LDI TOFMS). Gold clusters Au_m⁺ (m = 1 to ~35) were observed with a difference of one gold atom and their intensities were in decreasing order with respect to m. For P_n⁺ (n = 2 to ~111) clusters, the intensities of odd‐numbered phosphorus clusters are much higher than those for even‐numbered phosphorus clusters. During ablation of P‐nanogold mixtures, clusters Au_m⁺ (m = 1‐12), P_n⁺ (n = 2‐7, 9, 11, 13–33, 35–95 (odd numbers)), AuP_n⁺ (n = 1, 2–88 (even numbers)), Au₂P_n⁺ (n = 1‐7, 14–16, 21–51 (odd numbers)), Au₃P_n⁺ (n = 1‐6, 8, 9, 14), Au₄P_n⁺ (n = 1‐9, 14–16), Au₅P_n⁺ (n = 1‐6, 14, 16), Au₆P_n⁺ (n = 1‐6), Au₇P_n⁺ (n = 1‐7), Au₈P_n⁺ (n = 1‐6, 8), Au₉P_n⁺ (n = 1‐10), Au₁₀P_n⁺ (n = 1‐8, 15), Au₁₁P_n⁺ (n = 1‐6), and Au₁₂P_n⁺ (n = 1, 2, 4) were detected in positive ion mode. In negative ion mode, Au_m^– (m = 1–5), P_n^– (n = 2, 3, 5–11, 13–19, 21–35, 39, 41, 47, 49, 55 (odd numbers)), AuP_n^– (n = 4–6, 8–26, 30–36 (even numbers), 48), Au₂P_n^– (n = 2–5, 8, 11, 13, 15, 17), Au₃P_n^– (n = 6–11, 32), Au₄P_n^– (n = 1, 2, 4, 6, 10), Au₆P₅^–, and Au₇P₈^– clusters were observed. In both modes, phosphorus‐rich Au_mP_n clusters prevailed. The first experimental evidence for formation of AuP₆₀ and gold‐covered phosphorus Au₁₂P_n (n = 1, 2, 4) clusters is given. The new gold phosphides generated might inspire synthesis of new Au‐P materials with specific properties. Copyright © 2012 John Wiley & Sons, Ltd.     

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

Gold phosphides show unique optical or semiconductor properties and there are extensive high technology applications, e.g. in laser diodes, etc. In spite of the various AuP structures known, the search for new materials is wide. Laser ablation synthesis is a promising screening and synthetic method. Generation of gold phosphides via laser ablation of red phosphorus and nanogold mixtures was studied using laser desorption ionisation time-of-flight mass spectrometry (LDI TOFMS). Gold clusters Au(m)(+) (m?=?1 to ~35) were observed with a difference of one gold atom and their intensities were in decreasing order with respect to m. For P(n)(+) (n?=?2 to ~111) clusters, the intensities of odd-numbered phosphorus clusters are much higher than those for even-numbered phosphorus clusters. During ablation of P-nanogold mixtures, clusters Au(m)(+) (m?=?1-12), P(n)(+) (n?=?2-7, 9, 11, 13-33, 35-95 (odd numbers)), AuP(n)(+) (n?=?1, 2-88 (even numbers)), Au(2)P(n)(+) (n?=?1-7, 14-16, 21-51 (odd numbers)), Au(3)P(n)(+) (n?=?1-6, 8, 9, 14), Au(4)P(n)(+) (n?=?1-9, 14-16), Au(5)P(n)(+) (n?=?1-6, 14, 16), Au(6)P(n)(+) (n?=?1-6), Au(7)P(n)(+) (n?=?1-7), Au(8)P(n)(+) (n?=?1-6, 8), Au(9)P(n)(+) (n?=?1-10), Au(10)P(n)(+) (n?=?1-8, 15), Au(11)P(n)(+) (n?=?1-6), and Au(12)P(n)(+) (n?=?1, 2, 4) were detected in positive ion mode. In negative ion mode, Au(m)(-) (m?=?1-5), P(n)(-) (n?=?2, 3, 5-11, 13-19, 21-35, 39, 41, 47, 49, 55 (odd numbers)), AuP(n)(-) (n?=?4-6, 8-26, 30-36 (even numbers), 48), Au(2)P(n)(-) (n?=?2-5, 8, 11, 13, 15, 17), A(3) P(n)(-) (n?=?6-11, 32), Au(4)P(n)(-) (n?=?1, 2, 4, 6, 10), Au(6)P(5)(-), and Au(7)P(8)(-) clusters were observed. In both modes, phosphorus-rich Au(m)P(n) clusters prevailed. The first experimental evidence for formation of AuP(60) and gold-covered phosphorus Au(12)P(n) (n?=?1, 2, 4) clusters is given. The new gold phosphides generated might inspire synthesis of new Au-P materials with specific properties.     

Steady vortical flow around a finite plate

An explicit solution for a layer of fluid with constant vorticitysurrounding a thin plate of finite length is obtained usingelementary conformal mapping methods. In the limit of largeplate length the behaviour of the solution near the ends ofthe plate tends to that of the previously known solution fora semi-infinite plate. Contour dynamics is used to investigatethe stability of the steady solutions.     

Mass spectrometry of nanodiamonds

Detonation nanodiamonds (NDs) were studied by time‐of‐flight mass spectrometry (TOF MS). The formation of singly charged carbon clusters, C, with groups of clusters at n = 1–35, n ∼160–400 and clusters with n ∼8000 was observed. On applying either high laser energy or ultrasound, the position and intensity of the maxima change and a new group of clusters at n ∼70–80 is formed. High carbon clusters consist of an even number of carbons while the percentage of odd‐numbered clusters is quite low (≤5–10%). On increasing the laser energy, the maximum of ionization (at n ∼200 carbons) is shifted towards the lower m/z values. It is suggested that this is mainly due to the disaggregation of the original NDs. However, the partial destruction of NDs is also possible. The carbon clusters (n ∼2–35) are partially hydrogenated and the average value of the hydrogenation was 10–30%. Trace impurities in NDs like Li, B, Fe, and others were detected at high laser energy. Several matrices for ionizing NDs were examined and NDs themselves can also be used as a matrix for the ionization of various organic compounds. When NDs were used as a matrix for gold nanoparticles, the formation of various gold carbides Au_mC_n was detected and their stoichiometry was determined. It was demonstrated that TOF MS can be used advantageously to analyze NDs, characterize their size distribution, aggregation, presence of trace impurities and surface chemistry. Copyright © 2009 John Wiley & Sons, Ltd.     

Formation of aluminium, aluminium nitride and nitrogen clusters via laser ablation of nano aluminium nitride. Laser Desorption Ionisation and Matrix-Assisted Laser Desorption Ionisation Time-of-Flight Mass Spectrometry

Laser Desorption Ionisation (LDI) and Matrix-Assisted Laser Desorption Ionisation (MALDI) Time-of-Flight Mass Spectrometry (TOFMS) were used to study the pulsed laser ablation of aluminium nitride (AlN) nano powder. The formation of Al(m)(+) (m=1-3), N(n)(+) (n=4, 5), AlN(n)(+) (n=1-5, 19, 21), Al(m)N(+) (m=2-3), Al(3)N(2)(+), Al(9)N(n)(+) (n=5, 7, 9, 11 and 15), Al(11)N(n)(+) (n=4, 6, 10, 12, 19, 21, 23, and 25), and Al(13)N(n)(+) (n=25, 31, 32, 33, 34, 35, and 36) clusters was detected in positive ion mode. Similarly, Al(m)(-) (m=1-3), AlN(n)(-) (n=1-3, 5), Al(m)N(-) (n=2, 3), Al(2)N(n)(-) (n=2-4, 28, 30), N(n)(-) (n=2, 3), Al(4)N(7)(-) Al(8)N(n)(-) (n=1-6), and Al(13)N(n)(-) (n=9, 18, 20, 22, 24, 26, 28, 33, 35, 37, 39, 41 and 43) clusters were observed in negative ion mode. The formation of the stoichiometric Al(10) N(10) cluster was shown to be of low abundance. On the contrary, the laser ablation of nano-AlN led mainly to the formation of nitrogen-rich Al(m)N(n) clusters in both negative and positive ion mode. The stoichiometry of the Al(m)N(n) clusters was determined via isotopic envelope analysis and computer modelling.