Photoluminescent gold nanodots (Au NDs) are prepared via etching and codeposition of hybridized ligands, an antimicrobial peptide (surfactin; SFT), and 1‐dodecanethiol (DT), on gold nanoparticles (≈3.2 nm). As‐prepared ultrasmall SFT/DT–Au NDs (size ≈2.5 nm) are a highly efficient antimicrobial agent. The photoluminescence properties and stability as well as the antimicrobial activity of SFT/DT–Au NDs are highly dependent on the density of SFT on Au NDs. Relative to SFT, SFT/DT–Au NDs exhibit greater antimicrobial activity, not only to nonmultidrug‐resistant bacteria but also to the multidrug‐resistant bacteria. The minimal inhibitory concentration values of SFT/DT–Au NDs are much lower (>80‐fold) than that of SFT. The antimicrobial activity of SFT/DT–Au NDs is mainly due to the synergistic effect of SFT and DT–Au NDs on the disruption of the bacterial membrane. In vitro cytotoxicity and hemolysis analyses have revealed superior biocompatibility of SFT/DT–Au NDs than that of SFT. Moreover, in vivo methicillin‐resistant S. aureus–infected wound healing studies in rats show faster healing, better epithelialization, and are more efficient in the production of collagen fibers when SFT/DT–Au NDs are used as a dressing material. This study suggests that the SFT/DT–Au NDs are a promising antimicrobial candidate for preclinical applications in treating wounds and skin infections.

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Functional logic gates based on lead ions (Pb(2+)) and mercury ions (Hg(2+)) that induce peroxidase-like activities in gold nanoparticles (Au NPs) in the presence of platinum (Pt(4+)) and bismuth ions (Bi(3+)) are presented. The "AND" logic gate is constructed using Pt(4+)/Pb(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Pt(4+)/Pb(2+)(AND)-Au NPPOX". When Pt(4+) and Pb(2+) coexist, strong metallophilic interactions (between Pt and Pb atoms/ions) and aurophilic interactions (between Au and Pb/Pt atoms/ions) result in significant increases in the deposition of Pt and Pb atoms/ions onto the Au NPs, leading to enhanced peroxidase-like activity. The "INHIBIT" logic gate is fabricated by using Bi(3+) and Hg(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX". High peroxidase-like activity of Au NPs in the presence of Bi(3+) is a result of the various valence (oxidation) states of Bi(3+) and Au (Au(+)/Au(0)) atoms on the nanoparticle's surface. When Bi(3+) and Hg(2+) coexist, strong Hg-Au amalgamation results in a large decrease in the peroxidase-like activity of the Au NPs. These two probes (Pt(4+)/Pb(2+)(AND)-Au NPPOX and Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX) allow selective detection of Pb(2+) and Hg(2+) down to nanomolar quantities. The practicality of these two probes has been validated by analysis of Pb(2+) and Hg(2+) in environmental water samples (tap water, river water, and lake water). In addition, an integrated logic circuit based on the color change (formation of reddish resorufin product) and generation of O2 bubbles from these two probes has been constructed, allowing visual detection of Pb(2+) and Hg(2+) in aqueous solution.

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Hydrogen sulfide (H2S) is a highly toxic environmental pollutant and also an important gaseous transmitter. Therefore, selective detection of H2S is very important, and visual detection of it with the naked eye is preferred in practical applications. In this study, thiolated azido derivates and active esters functionalized gold nanoparticles (AE-AuNPs)-based nanosensors have been successfully prepared for H2S perception. The sensing principle consists of two steps: first, H2S reduces the azide group to a primary amine; second, a cross-linking reaction between the primary amine and active ester induces the aggregation of AuNPs. The AE-AuNPs-based nanosensors show high selectivity toward H2S over other anions and thiols due to the specific azide-H2S chemistry. Under optimal conditions, 0.2 μM H2S is detectable using a UV-vis spectrophotometer, and 4 μM H2S can be easily detected by the naked eye. In addition, the practical application of the designed nanosensors was evaluated with lake water samples.

In this study, we prepared photoluminescent l-cysteine (Cys)-capped gold nanoclusters (Cys-Au NCs) via NaBH-mediated reduction of aggregated coordination polymers (supramolecules) of -[Cys-Au(i)]-. The -[Cys-Au(i)]- supramolecules with interesting chiral properties were formed through simple reactions of chloroauric acid (HAuCl) with Cys at certain pH values (pH 3-7). The -[Cys-Au(i)]- polymers could self-assemble into -[Cys-Au(i)]- supramolecules with irregular morphologies and diameters larger than 500 nm through stacked hydrogen bonding and zwitterionic interactions between Cys ligands and through Au(i)Au(i) aurophilic interactions in solutions with pH values ≤7. The photoluminescent Au NCs (quantum yield = 11.6%) dominated by a Au core were embedded in -[Cys-Au(i)]- supramolecules after NaBH-mediated reduction. The optical and structural properties of Cys-Au NCs/-[Cys-Au(i)]- nanocomposites were investigated, revealing that the interaction between Cys ligands plays a critical role in the self-assembly of -[Cys-Au(i)]- supramolecules and in the formation of photoluminescent Cys-Au NCs embedded in the supramolecules. To further demonstrate that the photoluminescence properties and structures of the nanocomposites are mediated by the intermolecular forces of thiol ligands, other thiol ligands (l-penicillamine, l-homocysteine, 3-mercaptopropionic acid, and l-glutathione) and a ligand-crosslinking agent [bis(sulfosuccinimidyl) suberate; BS3] were used. We concluded that the electrostatic interactions, hydrogen bonding and steric effects dominate the polymer self-assembly into thiol-ligand-Au(i) supramolecules and thus the formation of Au NCs. Our study provides insights into the bottom-up synthesis of photoluminescent Au NCs from thiol-ligand-Au(i) complexes, polymers, and supramolecules. The hybrid Au NCs/-[Cys-Au(i)]- nanocomposites can potentially be employed as drug carriers and bioimaging agents.

The ubiquitous function of nitric oxide (NO) guided the biological discovery of the natural dinitrosyliron unit (DNIU) [Fe-(NO) 2 ] as an intermediate/end product after Fe nitrosylation of nonheme cofactors. Because of the natural utilization of this cofactor for the biological storage and delivery of NO, a bioinorganic study of synthetic dinitrosyliron complexes (DNICs) has been extensively explored in the last 2 decades. The bioinorganic study of DNICs involved the development of synthetic methodology, spectroscopic discrimination, biological application of NO-delivery reactivity, and translational application to the (catalytic) transformation of small molecules. In this Forum Article, we aim to provide a systematic review of spectroscopic and computational insights into the bonding nature within the DNIU [Fe(NO) 2 ] and the electronic structure of different types of DNICs, which highlights the synchronized advance in synthetic methodology and spectroscopic tools. With regard to the noninnocent nature of a NO ligand, spectroscopic and computational tools were utilized to provide qualitative/quantitative assignment of oxidation states of Fe and NO in DNICs with different redox levels and ligation modes as well as to probe the Fe−NO bonding interaction modulated by supporting ligands. Besides the strong antiferromagnetic coupling between high-spin Fe and paramagnetic NO ligands within the covalent DNIU [Fe(NO) 2 ], in polynuclear DNICs, the effects of the Fe•••Fe distance, nature of the bridging ligands, and type of bridging modes on the regulation of the magnetic coupling among paramagnetic DNIU [Fe(NO) 2 ] are further reviewed. In the last part of this Forum Article, the sequential reaction of {Fe(NO) 2 } 10 DNIC [(NO) 2 Fe(AMP)] (1-red) with NO (g) , HBF 4 , and KC 8 establishes a synthetic cycle, {Fe(NO) 2 } 9 -{Fe(NO) 2 } 9 DNIC [(NO) 2 Fe(μ-dAMP) 2 Fe(NO) 2 ] (1) → {Fe(NO) 2 } 9 DNIC [(NO 2 )Fe(AMP)][BF 4 ] (1-H) → {Fe(NO) 2 } 10 DNIC 1-red → DNIC 1, for the transformation of NO into HNO/N 2 O. Of importance, the NO-induced transformation of {Fe(NO) 2 } 10 DNIC 1-red and [(NO) 2 Fe(DTA)] (2-red; DTA = diethylenetriamine) unravels a synthetic strategy for preparation of the {Fe(NO) 2 } 9 -{Fe(NO) 2 } 9 DNICs [(NO) 2 Fe(μ-NHR) 2 Fe(NO) 2 ] containing amido-bridging ligands, which hold the potential to feature distinctive physical properties, chemical reactivities, and biological applications.