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Sulfathiazole is an antibiotic used to prevent diseases and promote animal growth, and may pose health risks to humans when consumed excessively. Herein, we prepared a nanosubstrate for trace determination using the surface-enhanced Raman scattering (SERS) technique by synthesizing spinous gold nanoparticles (SGNPs) through a rapid and straightforward seed-mediated method. Prior to detection, SGNPs with long tips were effectively synthesized by varying the seed solutions and the volume of ascorbic acid. These spinous nanostructures with long tips could improve the SERS detection of sulfathiazole (STZ) by creating more hot spots in the vicinity of particles. Furthermore, the SERS nano-substrate is facile to prepare with high sensitivity, and the testing sample does not undergo a complicated pretreatment procedure. The results show that nano-substrates can detect STZ at low concentrations ranging from 0.01 to 50 μg mL−1, with an excellent linear correlation between the concentration and intensity (R2 = 0.99). The limit of detection (LOD) reaches 0.22 μg mL−1, and the limit of quantification is 0.73 μg mL−1. In addition, the SERS nanosubstrate can exhibit good reproducibility with an RSD of 6.26%, as evaluated with STZ solution at a low concentration of 40 μg mL−1. The assignments of STZ Raman bands were performed using density-functional theory (DFT) quantum chemical calculations. The strong interaction affinity between Au atoms and STZ compounds was also described by calculating the binding energy of isolated species and Au20-STZ complexes. The STZ could be anchored on the Au surface through thiazole nitrogen. Furthermore, the calculated SERS spectrum of Au-STZ could be assigned to the experimental ones with the most enhanced signal near 1430 and 1540 cm−1. Potential applications that benefit from this SERS nanosubstrate are measurements for a variety of antibiotics. [ABSTRACT FROM AUTHOR]

The geometry of the neutral Au18 gold cluster was probed by a combination of quantum chemical calculations and far-infrared multiple photon dissociation (FIR-MPD) spectroscopy of a Kr messenger complex. Two low-lying isomers are identified to potentially contribute to the experimental IR spectrum, both being derived from a star-like Au17 structure upon capping with one extra Au atom either inside (18_1) or outside (18_5) the star. In particular, the present detection of structure 18_1 by DFT computations where a golden cage encapsulates an endohedral Au atom, is intriguing as a stable core–shell isomer has, to our knowledge, never been found before for such small neutral gold clusters. DFT and local coupled-cluster (DLPNO and PNO-CCSD(T)) computations indicate that both Au18 isomers are close to each other, within ∼3 kcal mol−1, on the energy scale. Although the exact energy ordering is again method-dependent and remains, at present, inconclusive, the most striking spectral signatures of both isomers are related to vibrational modes localized at atoms capping the inner pentaprism sub-structure that result in prominent peaks centered at ∼80 cm−1, close to the most prominent experimental feature found at 78 cm−1. The calculated IR spectra of both core–shell and hollow isomers are very similar to each other and both agree comparably well with the experimental FIR-MPD spectra of the Au18Kr1,2 complexes. [ABSTRACT FROM AUTHOR]

The Au17 gold cluster was experimentally produced in the gas phase and characterized by its vibrational spectrum recorded using far-IR multiple photon dissociation (FIR-MPD) of Au17Kr. DFT and coupled-cluster theory PNO-LCCSD(T)-F12 computations reveal that, at odds with most previous reports, Au17 prefers two star-like forms derived from a pentaprism added by two extra Au atoms on both top and bottom surfaces of the pentaprism, along with five other Au atoms each attached on a lateral face. A good agreement between calculated and FIR-MPD spectra indicates a predominant presence of these star-like isomers. Stabilization of a star form arises from strong orbital interactions of an Au12 core with a five-Au-atom string. [ABSTRACT FROM AUTHOR]

The onset of the transition from 2D to 3D structures in pure gold clusters remains a matter of continuing debate. In this theoretical study we revisit several planar and non-planar structural motifs of the size Au10 with the aim to clarify this issue. Computations using a long-range corrected exchange–correlation functional LC-BLYP, coupled-cluster theories CCSD(T) and PNO-LCCSD(T)-F12 reveal that, at variance with previous reports on the preference of a planar elongated hexagon, both planar and nonplanar isomers of the neutral Au10 are energetically degenerated up to 300 K. Its 3D equilibrium geometry is a core–shell structure which can be built up from a trigonal prism by capping four extra Au atoms outside. A comparison to the available experimental vibrational spectra allows us to argue that both lowest-lying 2D and 3D isomers of Au10 likely coexist in the molecular beam during measurement of its FIR spectra. This result also suggests that the 2D–3D transition of neutral gold clusters occurs at the size Au10. [ABSTRACT FROM AUTHOR]

Molecular structures and properties of the binary clusters containing twelve boron atoms mixed with n lithium atoms, B12Lin with n = 1–14, were investigated using density functional theory with the TPSSh functional and the 6-311+G(d) basis set. Energetic parameters including relative energies, average binding energies and second-order energies of the entire series were predicted using the coupled-cluster theory (U)CCSD(T) in conjunction with the cc-pVTZ basis set. Several lowest-lying isomers were determined for each size B12Lin whose energies differ from each other by <3 kcal mol−1, except for n = 1, 2 and 4 (≤5 kcal mol−1), and particularly n = 8 (∼13 kcal mol−1). Electronic structure and chemical bonding in some specific sizes such as B12Li4, B12Li8 and B12Li14 were analyzed in detail. We established the electron shells of some magic clusters such as the B12Li4 cone for which we proposed a mixed cone-disk electron shell model. Thanks to both the phenomenological shell and Clemenger–Nilsson models, B12Li8 which contains a specific set of shells of 44 valence electrons is a high stability species. The arrangement of Li atoms around a fullerene B12 framework shows that the mixed B12Li8 emerges as the most suitable of this cluster series to adsorb molecular hydrogen. Up to 32 H2 molecules can strongly be attached to the B12Li8 cluster which is thus predicted to be a realistic candidate for hydrogen storage material with gravimetric density reaching up to a theoritical limit of 26 wt%. Attachment of the fifth H2 molecule to each Li atom of B12Li8 results in weaker average bonds but can give rise to a total of 40 H2 molecules, corresponding to 30 wt% of hydrogen. [ABSTRACT FROM AUTHOR]

A recent paper by Rodríguez-Kessler et al., Phys. Chem. Chem. Phys., 2020, 22, 27255–27262, reported not only results of quantum chemical computations (using the PW91 density functional) on Ag16 clusters as emphasized in the article's title, but also on the Ag15 size. These authors confirmed previous results obtained by McKee and Samokhvalov (J. Phys. Chem. A, 2017, 121, 5018–5028 using the M06 density functional) that the most stable isomer of Ag15 is a C2v structure. We wish to point out that two low symmetry isomers of Ag15 that have a similar energy content are even lower in energy than their reported C2v global minimum. The relative energies between low-lying Ag15 isomers were again found to be method-dependent, and within the expected accuracy of DFT and CCSD(T) methods they could be considered as energetically degenerate, and likely coexist in a molecular beam. The new lower-energy Ag15 isomers appear to fit more consistently within the structural evolution of small silver clusters. [ABSTRACT FROM AUTHOR]

The smallest triple ring tube-like gold clusters M 2 @Au 15 q with M = Mo, W and q = 1, 0, -1 are reported for the first time. Incorporation of an M 2 dimer results in a remarkable modification of both atomic and electronic structures of the gold host. While the bare Au 15 cluster exhibits a 3D cage shape, the doubly doped clusters M 2 @Au 15 in all charge states are found to prefer a tubular form composed of three five-membered Au rings in an anti-prism arrangement and stabilized by an M 2 unit placed inside the tube-like Au 15 gold framework. The equilibrium geometry of both M 2 @Au 15 and M 2 @Au 15 - is not much modified upon electron detachment from or attachment to their pure gold counterpart. The anion M 2 @Au 15 - with 28 itinerant electrons establishes an electron shell configuration of 1S 2 1P 6 1D 10 2S 2 1F 8 , in which the 1F shell splits into four different sub-levels. These stable clusters are thus not magic. Computed results on the first and second hyper-polarizability parameters of the doped clusters show a strong dependence on the charge. Overall, the neutral M 2 @Au 15 is found to exhibit a particularly strong nonlinear optical (NLO) response. These clusters can also be extended to 1D nanowires, providing helpful guidance for the design of novel gold-based nanowires with rich optoelectronic properties.

The geometry of the neutral Au 18 gold cluster was probed by a combination of quantum chemical calculations and far-infrared multiple photon dissociation (FIR-MPD) spectroscopy of a Kr messenger complex. Two low-lying isomers are identified to potentially contribute to the experimental IR spectrum, both being derived from a star-like Au 17 structure upon capping with one extra Au atom either inside (18&#95;1) or outside (18&#95;5) the star. In particular, the present detection of structure 18&#95;1 by DFT computations where a golden cage encapsulates an endohedral Au atom, is intriguing as a stable core-shell isomer has, to our knowledge, never been found before for such small neutral gold clusters. DFT and local coupled-cluster (DLPNO and PNO-CCSD(T)) computations indicate that both Au 18 isomers are close to each other, within ∼3 kcal mol -1 , on the energy scale. Although the exact energy ordering is again method-dependent and remains, at present, inconclusive, the most striking spectral signatures of both isomers are related to vibrational modes localized at atoms capping the inner pentaprism sub-structure that result in prominent peaks centered at ∼80 cm -1 , close to the most prominent experimental feature found at 78 cm -1 . The calculated IR spectra of both core-shell and hollow isomers are very similar to each other and both agree comparably well with the experimental FIR-MPD spectra of the Au 18 Kr 1,2 complexes.

The Au 17 gold cluster was experimentally produced in the gas phase and characterized by its vibrational spectrum recorded using far-IR multiple photon dissociation (FIR-MPD) of Au 17 Kr. DFT and coupled-cluster theory PNO-LCCSD(T)-F12 computations reveal that, at odds with most previous reports, Au 17 prefers two star-like forms derived from a pentaprism added by two extra Au atoms on both top and bottom surfaces of the pentaprism, along with five other Au atoms each attached on a lateral face. A good agreement between calculated and FIR-MPD spectra indicates a predominant presence of these star-like isomers. Stabilization of a star form arises from strong orbital interactions of an Au 12 core with a five-Au-atom string.

The onset of the transition from 2D to 3D structures in pure gold clusters remains a matter of continuing debate. In this theoretical study we revisit several planar and non-planar structural motifs of the size Au 10 with the aim to clarify this issue. Computations using a long-range corrected exchange-correlation functional LC-BLYP, coupled-cluster theories CCSD(T) and PNO-LCCSD(T)-F12 reveal that, at variance with previous reports on the preference of a planar elongated hexagon, both planar and nonplanar isomers of the neutral Au 10 are energetically degenerated up to 300 K. Its 3D equilibrium geometry is a core-shell structure which can be built up from a trigonal prism by capping four extra Au atoms outside. A comparison to the available experimental vibrational spectra allows us to argue that both lowest-lying 2D and 3D isomers of Au 10 likely coexist in the molecular beam during measurement of its FIR spectra. This result also suggests that the 2D-3D transition of neutral gold clusters occurs at the size Au 10 .

Molecular structures and properties of the binary clusters containing twelve boron atoms mixed with n lithium atoms, B 12 Li n with n = 1-14, were investigated using density functional theory with the TPSSh functional and the 6-311+G(d) basis set. Energetic parameters including relative energies, average binding energies and second-order energies of the entire series were predicted using the coupled-cluster theory (U)CCSD(T) in conjunction with the cc-pVTZ basis set. Several lowest-lying isomers were determined for each size B 12 Li n whose energies differ from each other by <3 kcal mol -1 , except for n = 1, 2 and 4 (≤5 kcal mol -1 ), and particularly n = 8 (∼13 kcal mol -1 ). Electronic structure and chemical bonding in some specific sizes such as B 12 Li 4 , B 12 Li 8 and B 12 Li 14 were analyzed in detail. We established the electron shells of some magic clusters such as the B 12 Li 4 cone for which we proposed a mixed cone-disk electron shell model. Thanks to both the phenomenological shell and Clemenger-Nilsson models, B 12 Li 8 which contains a specific set of shells of 44 valence electrons is a high stability species. The arrangement of Li atoms around a fullerene B 12 framework shows that the mixed B 12 Li 8 emerges as the most suitable of this cluster series to adsorb molecular hydrogen. Up to 32 H 2 molecules can strongly be attached to the B 12 Li 8 cluster which is thus predicted to be a realistic candidate for hydrogen storage material with gravimetric density reaching up to a theoritical limit of 26 wt%. Attachment of the fifth H 2 molecule to each Li atom of B 12 Li 8 results in weaker average bonds but can give rise to a total of 40 H 2 molecules, corresponding to 30 wt% of hydrogen.

A recent paper by Rodríguez-Kessler et al., Phys. Chem. Chem. Phys., 2020, 22, 27255-27262, reported not only results of quantum chemical computations (using the PW91 density functional) on Ag 16 clusters as emphasized in the article's title, but also on the Ag 15 size. These authors confirmed previous results obtained by McKee and Samokhvalov (J. Phys. Chem. A, 2017, 121, 5018-5028 using the M06 density functional) that the most stable isomer of Ag 15 is a C 2v structure. We wish to point out that two low symmetry isomers of Ag 15 that have a similar energy content are even lower in energy than their reported C 2v global minimum. The relative energies between low-lying Ag 15 isomers were again found to be method-dependent, and within the expected accuracy of DFT and CCSD(T) methods they could be considered as energetically degenerate, and likely coexist in a molecular beam. The new lower-energy Ag 15 isomers appear to fit more consistently within the structural evolution of small silver clusters.