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The capping reagent plays an essential role in the functional properties of gold nanoparticles (AuNPs). Multiple stimuli responsive materials are generated via diverse surface modification. The ability of the organic ligand shell on gold surface to create a porous shell capable of binding small molecules is demonstrated as an approach to detect molecules, such as methane, that would be otherwise difficult to sense. Thiols are the most studied capping ligands of AuNPs used in chemiresistors. Phosphine capping groups are usually seemed as stabilizers in synthesis and catalysis. However, by virtue of the pyramidal shape of triarylphosphines, they are natural candidates to create intrinsic voids within the ligand shell of AuNPs. In this work, surface functionalized (capped) AuNPs with chelating phosphine ligands are synthesized via two synthetic routes, enabling chemiresistive methane gas detection at sub-100 ppm levels. These AuNPs are compared to thiol capped AuNPs, and studies were undertaken to evaluate structure-property relationships for their performance in the detection of hydrocarbons. Polymer overcoatings applied to the conductive networks of the functionalized AuNP arrays were shown to reduce resistivity by promoting the formation of conduction pathways with decreased core-core distance between nanoparticles. Observations made in the context of developing methane sensors, provides insight relevant to applications of phosphine or phosphine containing surface groups in functional AuNP materials.

Advances in new ligands in the last decade facilitated in‐depth studies on the property‐relationship of gold nanoclusters and promoted the rational synthesis and related applications of such materials. Currently, more and more new ligands are being explored; thus, the ligand library of AuNCs is being expanded fast, which also enables investigation of ligand effects of AuNCs via direct comparison of different ligating shell with the identical gold core. It is now widely accepted that ligands influence the properties of AuNCs enormously including stability, catalysis, photoluminescence among others. These studies inspired ligand engineering of AuNCs. One of the goals for ligand engineering is to develop ligated AuNC catalysts in which the ligands are able to exert big‐enough influence on electronic and steric control over catalysis as in a transition‐metal or an enzyme system. Although increasing attention is paid to the further expansion of ligand library, the investigation of design principles and strategies regarding ligands are still in their infant stage. This review summarizes the ligands for AuNC synthesis, the ligand effects on stability and catalysis, and recently developed strategies in promoting AuNC catalytic performance via ligand manipulation.

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Abstract. The decay of 2.4 h ll7gCd and 3.4 h t~TmCd has been investigated with the use of high-resolution Si(Li) and Ge(Li) detectors, also in an anti-Compton arrangement. Spectra from the two isomers have been resolved by comparing young reactor-produced HTCd with aged cyclotron-produced tt 7Cd" Ge(Li)-Ge(Li) coincidences have been measured with a multi-parameter analyzer. A hundred observed ),-rays are placed in a level scheme of ~tTIn. Possible theoretical interpretations are discussed. The I.T. Branching of 1~71n is (47.1 _+ 1.5)~o. Only about 1 ~o of 11/2-tt~mCd decays to 1.93 h 1/2 117"In and 10.9 o~ of 1/2 + t~VgCd decays to the 9/2 + ~Vgln ground state bypassing the isomeric In state.

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