γ-Alumina-supported Pt17 cluster: controlled loading, geometrical structure, and size-specific catalytic activity for carbon monoxide and propylene oxidation.

Although Pt is extensively used as a catalyst to purify automotive exhaust gas, it is desirable to reduce Pt consumption through size reduction because Pt is a rare element and an expensive noble metal. In this study, we successfully loaded a Pt17 cluster on γ-alumina (γ-Al2O3) (Pt17/γ-Al2O3) using [Pt17(CO)12(PPh3)8]Cl n (n = 1, 2) as a precursor. In addition, we demonstrated that Pt is not present in the form of an oxide in Pt17/γ-Al2O3 but instead has a framework structure as a metal cluster. Moreover, we revealed that Pt17/γ-Al2O3 exhibits higher catalytic activity for carbon monoxide and propylene oxidation than γ-Al2O3-supported larger Pt nanoparticles (PtNP/γ-Al2O3) prepared using the conventional impregnation method. Recently, our group discovered a simple method for synthesizing the precursor [Pt17(CO)12(PPh3)8]Cl n . Furthermore, Pt17 is a Pt cluster within the size range associated with high catalytic activity. By combining our established synthesis and loading methods, other groups can conduct further research on Pt17/γ-Al2O3 to explore its catalytic activities in greater depth.

Halopiger thermotolerans sp. nov., a thermo-tolerant haloarchaeon isolated from commercial salt.

Three thermo-tolerant halophilic archaeal strains, SR-441T, SR-412 and SR-188, were isolated from commercial salt samples. Cells were non-motile pleomorphic rod-shaped, and stained Gram-negative. Colonies were pink-pigmented. The three strains were able to grow with 1.7-4.6 M NaCl (optimum, 2.5 M), at pH 6.5-9.0 (optimum, pH 8.0) and at 35-60 °C (optimum, 45 °C). The orthologous 16S rRNA gene sequence similarities amongst the three strains were 98.8-99.3 %, and the level of DNA-DNA relatedness was 71-74 and 72-75 % (reciprocally). The closest relative was Halopiger aswanensis JCM 11628T with 98.6 %-99.1 % similarity in the orthologous 16S rRNA gene sequences, followed by two more Halopiger species, Halopiger xanaduensis JCM 14033T (98.5 %-99.1 %) and Halopiger salifodinae JCM 9578T (95.5 %-95.6 %). DNA-DNA relatednesses between the three strains and H. aswanensis JCM 11628T and H. xanaduensis JCM 14033T were 61 and 54 %, respectively. The polar lipids of the three novel strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, and bis-sulfated diglycosyl archaeol-1. The most distinctive feature of the three strains was the ability to grow at 60 °C, while the maximum growth temperature of H. aswanensis is 55 °C. Based on phenotypic and phylogenetic analyses, the isolates are considered to represent a novel species of the genus Halopiger, for which the name Halopiger thermotolerans sp. nov. is proposed. The type strain is SR-441T (=JCM 19583T=KCTC 4248T) isolated from solar salt produced in Australia. SR-412 (=JCM 19582) and SR-188 (=JCM 19581) isolated from commercial salt samples are additional strains of the species.

Natronoarchaeum philippinense sp. nov., a haloarchaeon isolated from commercial solar salt.

A Gram-staining-negative, pleomorphic, aerobic, halophilic archaeon, designated strain 294-194-5(T), was isolated in Japan from commercial solar salt imported from the Philippines. Colonies of strain 294-194-5(T) were translucent and red. Strain 294-194-5(T) was able to grow at 20-50 °C (optimum, 37-45 °C), with 14-30 % (w/v) NaCl (optimum, 18 %), and at pH 6.5-8.5 (optimum, pH 8.0). MgCl2 was not required for growth. Phylogenetic analysis based on 16S rRNA gene sequence similarities showed that strain 294-194-5(T) was most closely related to Natronoarchaeum mannanilyticum YSM-123(T) (96.8-97.1 % sequence similarities). The major polar lipids of the novel strain were the C20C20 and C20C25 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester and the same glycolipids (disulfated diglycosyl diether and one unidentified glycolipid) as detected in N. mannanilyticum YSM-123(T). The DNA G+C content of strain 294-194-5(T) was 63.0 mol%. The DNA-DNA relatedness values between the novel strain and N. mannanilyticum YSM-123(T)were 46.5 % and 48.5 % (reciprocal). Based on these data, strain 294-194-5(T) represents a novel species of the genus Natronoarchaeum, for which the name Natronoarchaeum philippinense sp. nov. is proposed. The type strain is 294-194-5(T) ( = JCM 16593(T) = CECT 7630(T)).

Soft- and reactive-landing of Cr(aniline)2 sandwich complexes onto self-assembled monolayers: separation between functional and binding sites.

Soft- and reactive-landing of gas-phase synthesized cationic Cr(aniline)(2) complexes onto self-assembled monolayers of methyl-terminated (CH(3)-SAM) and carboxyl-terminated (COOH-SAM) organothiolates coated on gold were performed at hyperthermal collision energy (5-20 eV). The properties of the Cr(aniline)(2) complexes on the SAM surfaces were characterized using infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD), together with theoretical calculations based on density functional theory (DFT). For the CH(3)-SAM, the Cr(aniline)(2) complexes were embedded inside the SAM matrix in a neutral charge state, keeping a sandwich structure. For the COOH-SAM, the IRAS and TPD study revealed that the amine-containing Cr(aniline)(2) complexes were bound to the SAM surface in two forms of physisorption and chemical linking through an amide bond. In the desorption, the latter form appeared as the reaction product between organothiolates and Cr(aniline)(2) above 400 K, where the organothiolate molecules, forming the SAM, were desorbed from the gold surface. The results show that the hyperthermal depositions onto a COOH-SAM bring about reactive-landing followed by covalent linking of an amide bond between the amine-containing Cr(aniline)(2) complexes to the carboxyl-terminated SAM surface, in which the binding sites can be separated from the functional sites of the d-π interaction.

Halostagnicola alkaliphila sp. nov., an alkaliphilic haloarchaeon from commercial rock salt.

A Gram-negative, pleomorphic, aerobic, haloalkaliphilic archaeon, strain 167-74(T), was isolated from commercial rock salt imported into Japan from China. Phylogenetic analysis based on 16S rRNA gene sequence similarities showed that strain 167-74(T) is closely related to Halostagnicola larsenii XH-48(T) (98.3 %) and Halostagnicola kamekurae 194-10(T) (97.2 %). The major polar lipids of the isolate were C(20)C(20) and C(20)C(25) derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. A glycolipid was not detected, in contrast to the two existing, neutrophilic species of the genus Halostagnicola. The DNA G+C content of strain 167-74(T) was 60.7 mol%. and it gave DNA-DNA reassociation values of 19.5 and 18.8 %, respectively, with Hst. larsenii JCM 13463(T) and Hst. kamekurae 194-10(T). Therefore, strain 167-74(T) represents a novel species, for which the name Halostagnicola alkaliphila sp. nov. is proposed, with the type strain 167-74(T) ( = JCM 16592(T)  = CECT 7631(T)).

Halostagnicola kamekurae sp. nov., an extremely halophilic archaeon from solar salt.

A novel extremely halophilic archaeon, strain 194-10(T), was isolated from a solar salt sample imported into Japan from the Philippines. Strain 194-10(T) was pleomorphic, neutrophilic and mesophilic and required at least 10 % (w/v) NaCl but no MgSO(4) . 7H(2)O for growth; it exhibited optimal growth at 15 % (w/v) NaCl and 60 mM MgSO(4) . 7H(2)O. Strain 194-10(T) grew at 20-45°C (optimum, 30°C) and pH 6.0-9.0 (optimum, pH 6.5-7.0). The G+C content of its DNA was 59.8 mol%. 16S rRNA gene sequence analysis revealed closest proximity to Halostagnicola larsenii XH-48(T) (98.5 % similarity), the sole representative of the genus Halostagnicola. Polar lipid analysis revealed that strain 194-10(T) contained phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester (the latter derived from both C(20)C(20) and C(20)C(25) archaeol) and several unidentified glycolipids. The results of DNA-DNA hybridization (20.7 % relatedness between Hst. larsenii JCM 13463(T) and strain 194-10(T)) and physiological and biochemical characteristics allowed differentiation of strain 194-10(T) from Hst. larsenii XH-48(T). Therefore, strain 194-10(T) represents a novel species of the genus Halostagnicola, for which the name Halostagnicola kamekurae sp. nov. is proposed, with the type strain 194-10(T) (=DSM 22427(T) =JCM 16110(T) =CECT 7536(T)).

Halarchaeum acidiphilum gen. nov., sp. nov., a moderately acidophilic haloarchaeon isolated from commercial solar salt.

A novel halophilic archaeon, strain MH1-52-1(T), was isolated from solar salt imported from Australia. Cells were pleomorphic, non-motile and Gram-negative. Strain MH1-52-1(T) required at least 3.0 M NaCl and 1 mM Mg(2+) for growth. Strain MH1-52-1(T) was able to grow at pH 4.0-6.0 (optimum, pH 4.4-4.5) and 15-45 °C (optimum, 37 °C). The diether phospholipids phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester, derived from both C(20)C(20) and C(20)C(25) archaeol, were present. Four unidentified glycolipids were also detected. The 16S rRNA gene sequence showed the highest similarity to that of Halobacterium noricense A1(T) (91.7%); there were lower levels of similarity to other members of the family Halobacteriaceae. The G+C content of its DNA was 61.4 mol%. Based on our phenotypic, genotypic and phylogenetic analyses, it is proposed that the isolate should be classified as a representative of a new genus and species, for which the name Halarchaeum acidiphilum gen. nov., sp. nov. is proposed. The type strain of Halarchaeum acidiphilum is MH1-52-1(T) (=JCM 16109(T) =DSM 22442(T) =CECT 7534(T)).

Room-temperature isolation of V(benzene)2 sandwich clusters via soft-landing into n-alkanethiol self-assembled monolayers.

The adsorption state and thermal stability of V(benzene)2 sandwich clusters soft-landed onto a self-assembled monolayer of different chain-length n-alkanethiols (Cn-SAM, n = 8, 12, 16, 18, and 22) were studied by means of infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD). The IRAS measurement confirmed that V(benzene)2 clusters are molecularly adsorbed and maintain a sandwich structure on all of the SAM substrates. In addition, the clusters supported on the SAM substrates are oriented with their molecular axes tilted 70-80 degrees off the surface normal. An Arrhenius analysis of the TPD spectra reveals that the activation energy for the desorption of the supported clusters increases linearly with the chain length of the SAMs. For the longest chain C22-SAM, the activation energy reaches approximately 150 kJ/mol, and the thermal desorption of the supported clusters can be considerably suppressed near room temperature. The clear chain-length-dependent thermal stability of the supported clusters observed here can be explained well in terms of the cluster penetration into the SAM matrixes.

Soft-landing isolation of vanadium-benzene sandwich clusters on a room-temperature substrate using n-alkanethiolate self-assembled monolayer matrixes.

Gas-phase synthesized vanadium-benzene 1:2 (VBz(2)) sandwich clusters were size-selectively deposited onto bare gold and long-chain n-alkanethiolate [-S-(CH(2))(n-1)-CH(3); n = 16, 18, and 22] self-assembled monolayer (SAM)-coated gold substrates under ultrahigh vacuum (UHV) conditions. Investigation of the resulting deposited clusters was performed by infrared reflection absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). The IR frequencies of the soft-landed VBz(2) clusters show excellent agreement with the fundamentals reported in IR data of VBz(2) in an argon matrix. The analysis of IRAS spectra reveals that while there was no orientational preference of the VBz(2) clusters on a bare gold substrate, the VBz(2) clusters deposited onto the SAM substrates were highly oriented with the molecular axis 70-80 degrees tilted off the surface normal. In addition, analysis of TDS spectra revealed unusually large adsorption heats of the physisorbed VBz(2) clusters. The present results are explained by cluster penetration into the long-chain alkanethiolate SAM and for the first time demonstrate the matrix isolation of gas-phase organometallic clusters around room temperature.