Six New Members of the A₂M^IIM^IV₃Q₈ Family and Their Structural Relationship

The A₂M^IIM^IV₃Q₈ family (A = alkali metal; M^II = divalent metal; M^IV = tetravalent metal; Q = chalcogenide) has attracted much attention because of its diverse structures and properties. Herein, we have successfully synthesized six new compounds as the first Mn-containing members of this family, Cs₂MnGe₃S₈ (<b>1</b>), Cs₂MnGe₃Se₈ (<b>2</b>), Cs₂MnSn₃Se₈ (<b>3</b>), Rb₂MnGe₃S₈ (<b>4</b>), Rb₂MnGe₃Se₈ (<b>5</b>), and Rb₂MnSn₃Se₈ (<b>6</b>). Compounds <b>1</b> and <b>6</b> crystallize in the monoclinic space group <i>P</i>2₁/<i>n</i> (No. 14) and <i>P</i>2₁ (No. 4), respectively, whereas compounds <b>2</b>–<b>5</b> crystallize in the non-centrosymmetric orthorhombic <i>P</i>2₁2₁2₁ (No. 19). According to our theoretical calculations, their energy gaps are mainly dominated by s states of M^IV and p states of Q and minor Mn 3d. Plate-like crystals with sizes about 20 × 5 × 1 mm³ of <b>2</b> and <b>3</b> are obtained by the Bridgeman method. In addition, we propose a structure mismatch factor that is defined as <i>F</i> = <i>r</i>_M^_II+ <i>r</i>_M^_IV + 2<i>r</i>_Q^_2– – 2<i>r</i>_A^₊ to provide a clear description of how three different structure types distribute among the A₂M^IIM^IV₃Q₈ family; when 1.2 < <i>F</i> < 1.9, members will adopt a <i>P</i>2₁2₁2₁-type structure; when <i>F</i> is too small (<1.2) or too large (>1.9), <i>P</i>2₁/<i>n</i> or <i>P</i>2₁-type, respectively, will be taken

Cs₂Ge₃In₆Se₁₄: A Structure Transformation Driven by the Size Preference and Its Properties

The new selenide Cs₂Ge₃In₆Se₁₄, featuring its own structure type with germanium in mixed-valence states, is discovered via a solid-state reaction at 1173 K. The compound crystallizes in the <i>R</i>3̅<i>m</i> space group with <i>a</i> = 7.9951(6) Å and <i>c</i> = 41.726(4) Å. Two adjacent condensed layers of InSe₄ tetrahedra are linked by a [Ge²⁺Se₆] octahedron into a double slice that is further stacked along the <i>c</i> direction with a packing sequence of ···<i>abca</i>··· through the [Ge³⁺₂Se₆] dimer via its Ge–Ge metallic bond. The coexistence of Ge²⁺/Ge³⁺ and Ge–Ge metallic bonding has been confirmed by XPS and ELF analyses, respectively. More interestingly, although sharing many structure similarities, Cs₂Ge₃In₆Se₁₄ and our previously reported Cs₂Ge₃In₆Te₁₄ reveal a <i>R</i>3̅<i>m</i> to <i>P</i>3̅<i>m</i>1 structure transformation with a tripled <i>c</i> parameter. Single-crystal diffraction data and a thorough structure survey of related compounds point out that such a transformation is driven by the size preference of the [Ge₂Q₆] dimer. The title compound possesses a band gap of 2.08 eV and shows photodegradation of RhB under visible light that is more efficient than that for the commercial P25

Combining the Single-Atom Engineering and Ligand-Exchange Strategies: Obtaining the Single-Heteroatom-Doped Au₁₆Ag₁(S-Adm)₁₃ Nanocluster with Atomically Precise Structure

Obtaining cognate single-heteroatom doping is highly desirable but least feasible in the research of nanoclusters (NCs). In this work, we reported a new Au₁₆Ag₁(S-Adm)₁₃ NC, which is synthesized by the combination of single-atom engineering and ligand-exchange strategies. This new NC is so far the smallest crystallographically characterized Au-based NC protected by thiolate. The Au₁₆Ag₁(S-Adm)₁₃ exhibited a tristratified Au₃–Au₂Ag₁–Au₁ kernel capped by staple-like motifs including one dimer and two tetramers. In stark contrast to the size-growth from Au₁₈(S–C₆H₁₁)₁₄ to Au₂₁(S-Adm)₁₅ via just the ligand-exchange method, combining single Ag doping on Au₁₈(S–C₆H₁₁)₁₄ resulted in the size-decrease from Au₁₇Ag₁(S–C₆H₁₁)₁₄ to Au₁₆Ag₁(S-Adm)₁₃. DFT calculations were performed to both homogold Au₁₈ and single-heteroatom-doped Au₁₇Ag₁ to explain the opposite results under the same ligand-exchange reaction. Our work is expected to inspire the synthesis of new cognate single-atom-doped NCs by combining single-atom engineering and ligand-exchange strategies and also shed light on extensive understanding of the metal synergism effect in the NC range

Theoretical Predictions of a New ∼14 kDa Core-Mass Thiolate-Protected Gold Nanoparticle: Au₆₈(SR)₃₆

As an important intermediate link between the smaller and larger size thiolate-protected gold nanoparticles (RS-AuNPs), the molecular formula and atomic structure of the ∼14 kDa core-mass RS-AuNP species (containing around 70 core gold atoms) have not been determined unambiguously. In this work, we theoretically predict an unprecedented ∼14 kDa core-mass AuNP species, denoted as Au₆₈(SR)₃₆, which is composed a symmetric, face-centered-cubic (fcc) 68-gold atom framework. The fcc gold kernel in the Au₆₈(SR)₃₆ is made of eight 13-atom Au-cubotahedrons sharing 12 square faces, showing a standard 2 × 2 × 2 magic cube formula. The Au₆₈(SR)₃₆ is thought to be a key intermediate NP bridging the evolution of Au₄₄(SR)₂₈ and Au₉₂(SR)₄₄. The DFT calculations indicate the Au₆₈(SR)₃₆ has a sizable HOMO–LUMO gap of 0.98 eV and relative high thermodynamic stability. The fcc 68-atom gold framework in the Au₆₈(SR)₃₆ also presents a new candidate to address the atomic structure of recently reported water-soluble mercaptobenzoic acid protected Au₆₈NPs

Structure and Electronic Structure Evolution of Thiolate-Protected Gold Nanoclusters Containing Quasi Face-Centered-Cubic Kernels

A structure evolution map of face-centered cubic (fcc)-structured thiolate-ligand protected gold nanoclusters is outlined on the basis of total structure determination of a new 6e Au₂₁(SR)₁₅ (R = <i>tert</i>-butyl, <i>t</i>-Bu) cluster. The structural evolution map described some basic structural evolution patterns such as a triangle-Au₃ and tetrahedron-Au₄ associated gold-core evolution pattern and the periodic or symmetric growth of gold cores and ligand shells. According to the structural evolution map, a topological structure–electronic structure relationship is also proposed. The delocalized valence electronic properties of any fcc-structured gold clusters may be expressed as the linear combinations of the molecular orbitals of the fragment 2e units (Au₃⁺ and Au₄²⁺). The structural disciplines and topological structure–electronic structure relationships reported in this work laid a basis for understanding the structural evolution and electronic structure of fcc-structured thiolate-protected gold nanoclusters. Particularly, the established structural evolution map provides a tool to explore new magic-sized clusters and cluster structures. In this work, a new fcc-structured 4e Au₁₇(SR)₁₃ and a new isomer structure of the 8e Au₂₈(SR)₂₀ cluster were predicted. The medium-sized fcc-structured gold clusters locating in the size range from 52 to 92 gold atoms and even larger-sized gold clusters can be also explored from the structural regularities described in the map

Structure and Electronic Structure Evolution of Thiolate-Protected Gold Nanoclusters Containing Quasi Face-Centered-Cubic Kernels

A structure evolution map of face-centered cubic (fcc)-structured thiolate-ligand protected gold nanoclusters is outlined on the basis of total structure determination of a new 6e Au₂₁(SR)₁₅ (R = <i>tert</i>-butyl, <i>t</i>-Bu) cluster. The structural evolution map described some basic structural evolution patterns such as a triangle-Au₃ and tetrahedron-Au₄ associated gold-core evolution pattern and the periodic or symmetric growth of gold cores and ligand shells. According to the structural evolution map, a topological structure–electronic structure relationship is also proposed. The delocalized valence electronic properties of any fcc-structured gold clusters may be expressed as the linear combinations of the molecular orbitals of the fragment 2e units (Au₃⁺ and Au₄²⁺). The structural disciplines and topological structure–electronic structure relationships reported in this work laid a basis for understanding the structural evolution and electronic structure of fcc-structured thiolate-protected gold nanoclusters. Particularly, the established structural evolution map provides a tool to explore new magic-sized clusters and cluster structures. In this work, a new fcc-structured 4e Au₁₇(SR)₁₃ and a new isomer structure of the 8e Au₂₈(SR)₂₀ cluster were predicted. The medium-sized fcc-structured gold clusters locating in the size range from 52 to 92 gold atoms and even larger-sized gold clusters can be also explored from the structural regularities described in the map

Total Structure Determination of Au₂₁(S-Adm)₁₅ and Geometrical/Electronic Structure Evolution of Thiolated Gold Nanoclusters

The larger size gold nanoparticles typically adopt a face-centered cubic (fcc) atomic packing, while in the ultrasmall nanoclusters the packing styles of Au atoms are diverse, including fcc, hexagonal close packing (hcp), and body-centered cubic (bcc), depending on the ligand protection. The possible conversion between these packing structures is largely unknown. Herein, we report the growth of a new Au₂₁(S-Adm)₁₅ nanocluster (S-Adm = adamantanethiolate) from Au₁₈(SR)₁₄ (SR = cyclohexylthiol), with the total structure determined by X-ray crystallography. It is discovered that the hcp Au₉-core in Au₁₈(SR)₁₄ is transformed to a fcc Au₁₀-core in Au₂₁(S-Adm)₁₅. Combining with density functional theory (DFT) calculations, we provide critical information about the growth mechanism (geometrical and electronic structure) and the origin of fcc-structure formation for the thiolate-protected gold nanoclusters

Structure and Electronic Structure Evolution of Thiolate-Protected Gold Nanoclusters Containing Quasi Face-Centered-Cubic Kernels

A structure evolution map of face-centered cubic (fcc)-structured thiolate-ligand protected gold nanoclusters is outlined on the basis of total structure determination of a new 6e Au₂₁(SR)₁₅ (R = <i>tert</i>-butyl, <i>t</i>-Bu) cluster. The structural evolution map described some basic structural evolution patterns such as a triangle-Au₃ and tetrahedron-Au₄ associated gold-core evolution pattern and the periodic or symmetric growth of gold cores and ligand shells. According to the structural evolution map, a topological structure–electronic structure relationship is also proposed. The delocalized valence electronic properties of any fcc-structured gold clusters may be expressed as the linear combinations of the molecular orbitals of the fragment 2e units (Au₃⁺ and Au₄²⁺). The structural disciplines and topological structure–electronic structure relationships reported in this work laid a basis for understanding the structural evolution and electronic structure of fcc-structured thiolate-protected gold nanoclusters. Particularly, the established structural evolution map provides a tool to explore new magic-sized clusters and cluster structures. In this work, a new fcc-structured 4e Au₁₇(SR)₁₃ and a new isomer structure of the 8e Au₂₈(SR)₂₀ cluster were predicted. The medium-sized fcc-structured gold clusters locating in the size range from 52 to 92 gold atoms and even larger-sized gold clusters can be also explored from the structural regularities described in the map

Total Structure Determination of Au₂₁(S-Adm)₁₅ and Geometrical/Electronic Structure Evolution of Thiolated Gold Nanoclusters

The larger size gold nanoparticles typically adopt a face-centered cubic (fcc) atomic packing, while in the ultrasmall nanoclusters the packing styles of Au atoms are diverse, including fcc, hexagonal close packing (hcp), and body-centered cubic (bcc), depending on the ligand protection. The possible conversion between these packing structures is largely unknown. Herein, we report the growth of a new Au₂₁(S-Adm)₁₅ nanocluster (S-Adm = adamantanethiolate) from Au₁₈(SR)₁₄ (SR = cyclohexylthiol), with the total structure determined by X-ray crystallography. It is discovered that the hcp Au₉-core in Au₁₈(SR)₁₄ is transformed to a fcc Au₁₀-core in Au₂₁(S-Adm)₁₅. Combining with density functional theory (DFT) calculations, we provide critical information about the growth mechanism (geometrical and electronic structure) and the origin of fcc-structure formation for the thiolate-protected gold nanoclusters

Highly Bright Self-Assembled Copper Nanoclusters: A Novel Photoluminescent Probe for Sensitive Detection of Histamine

In this work, highly photoluminescent (PL) self-assembled copper nanoclusters (Cu NCs) capable of rapid, sensitive, and selective detection of histamine were developed. Cu NCs were synthesized in facile conditions by using 2,3,5,6-tetrafluorothiophenol (TFTP) as both the reducing agent and the protecting ligand, which exhibited intense saffron yellow (590 nm) PL via self-assembled induced emission (SAIE), and the absolute quantum yield (QY) of assembly was as high as 43.0%. The size, electronic states, and morphologies of the assembled nanoribbons were characterized, and the geometric structure and spectral properties of the Cu NCs were investigated by theoretical study. Furthermore, the mechanism of the excellent sensing performance of Cu NCs toward histamine was demonstrated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDX). With this sensing system, the amount of histamine in fish, shrimp, and red wine were analyzed, and experiment results verified the application of the sensor. Importantly, the luminescent test strips based on Cu NCs were fabricated for colorimetric detection of histamine in foods. This proposed technique may provide an alternative to traditional methods for histamine detection