Recent studies have shown that gold nanoparticles (AuNPs) functionalized with Zn(II) complexes can cleave phosphate esters and nucleic acids. Remarkably, such synthetic nanonucleases appear to catalyze metal (Zn)-aided hydrolytic reactions of nucleic acids similar to metallonuclease enzymes. To clarify the reaction mechanism of these nanocatalysts, here we have comparatively analyzed two nanonucleases with a >10-fold difference in the catalytic efficiency for the hydrolysis of the 2-hydroxypropyl-4-nitrophenylphosphate (HPNP, a typical RNA model substrate). We have used microsecond-long atomistic simulations, integrated with NMR experiments, to investigate the structure and dynamics of the outer coating monolayer of these nanoparticles, either alone or in complex with HPNP, in solution. We show that the most efficient one is characterized by coating ligands that promote a well-organized monolayer structure, with the formation of solvated bimetallic catalytic sites. Importantly, we have found that these nanoparticles can mimic two-metal-ion enzymes for nucleic acid processing, with Zn ions that promote HPNP binding at the reaction center. Thus, the two-metal-ion-aided hydrolytic strategy of such nanonucleases helps in explaining their catalytic efficiency for substrate hydrolysis, in accordance with the experimental evidence. These mechanistic insights reinforce the parallelism between such functionalized AuNPs and proteins toward the rational design of more efficient catalysts.

Properly designed monolayer-protected nanoparticles (2 nm core diameter) can be used as nanoreceptors for selective detection and identification of phenethylamine derivatives (designer drugs) in water. The molecular recognition mechanism is driven by the combination of electrostatic and hydrophobic interactions within the coating monolayer. Each nanoparticle can bind up to 30–40 analyte molecules. The affinity constants range from 10⁵ to 10⁶ M⁻¹ and are modulated by the hydrophobicity of the aromatic moiety in the substrate. Detection of drug candidates (such as amphetamines and methamphetamines) is performed by using magnetization (NOE) or saturation (STD) transfer NMR experiments. In this way, the NMR spectrum of the drug is isolated from that of the mixture, allowing broad-class multianalyte detection and even identification of unknowns. The introduction of a dimethylsilane moiety in the coating monolayer allows performing STD experiments in complex mixtures. In this way, a detection limit of 30 μM is reached with standard instruments.

A supramolecular nanozyme for the photocatalytic conversion of a Pt(IV) anticancer complex to cisplatin is described herein. We employed 1.9 nm Au nanoparticles decorated with thiol ligands bearing a TACN (1,4,7-triazacyclononane) headgroup to encapsulate FMN (riboflavin-5′-phosphate). In the presence of an electron donor, flavin-loaded nanoparticles photocatalyzed the reductive activation of the prodrug cis,cis,trans-[Pt(NH₃)₂(Cl₂)(O₂CCH₂CH₂COOH)₂] to cisplatin, achieving turnover frequency values of 7.4 min⁻¹.

Self-assembled gold nanoparticles onto colloidal silica nanoparticles exhibited higher magnetization transfer efficiencies in NMR chemosensing experiments, allowing the detection of analytes as low as 10 μM.

The reaction between the iminophosphorane ligand N-phenyl-1,1,1-triphenylphosphanimine (NPh=PPh₃) and anhydrous manganese(II) halides allowed the isolation of complexes with the general formula [MnX₂(NPh=PPh₃)₂] (X = Cl, Br, I). The compounds showed luminescence in the green region attributed to the ⁴T₁(⁴G)→⁶A₁(⁶S) transition of the metal centre in the tetrahedral field, which was superimposed in the cases of X = Cl and X = Br on weak ligand-centred fluorescence. The emission and excitation spectra were compared with those of the free ligand and of the related zinc(II) bromo-complex. DFT calculations on the free ligand and on the manganese(II) bromo-complex helped to rationalise the experimental data. The protonation of NPh=PPh₃ led to the formation of the iminium cation [NHPh=PPh₃]⁺, which was used as a building block for the synthesis of organic–inorganic hybrids with the general formula [NHPh=PPh₃]₂[MnX₄] (X = Cl, Br, I). The crystal structure of [NHPh=PPh₃]₂[MnBr₄] was determined by means of X-ray diffraction. Green photoluminescence associated with the metal-centred transition was also observed for the organic–inorganic hybrids, with higher quantum yields with respect to the neutral [MnX₂(NPh=PPh₃)₂] complexes. In the case of X = I, luminescence from the cation was superimposed on that from the tetraiodomanganate anion upon excitation of the compound with near–UV light.

The identification of psychoactive substances, in particular of designer drugs, on the site of their discovery is crucial to contrast the diffusion of drugs of abuse. We report here the first example of a nanoscale colorimetric probe, based on the nanoconfinement of a tricyclic dye and the target analytes in the cavity of cucurbit[8]uril. The probe selectively responds to NBOMes, with a limit of detection of 3 μM. The sensing system can be deposited on paper, thus obtaining a colorimetric strip test capable to discriminate illegal drugs from other substances of common use.