Macromonomers [RPhSiO 1.5 ] 8,10,12 and [RCH CHSiO 1.5 ] 8,10,12 , where R is a conjugated group, have previously been shown to offer photophysical properties wherein excitation promotes an electron from the HOMO to an excited-state LUMO that sits in the center of the cage and allows communication between all conjugated groups, suggesting 3-D delocalization. In the current work, we explore replacing one conjugated group in [RPhSiO 1.5 ] 8 with either Me or nPr or s i m p l y r e m o v i n g o n e c o r n e r f r o m t h e c a g e , [RPhSiO 1.5 ] 7 (O 0.5 SiMe 3 ) 3 , and examine its effect on any potential LUMO that might form. We report here that such changes seem to have no effect on the existence of a 3-D LUMO-derived delocalization as witnessed by emission redshifts from the R = 4-Me-/4-CN-stilbene moieties essentially identical to those for the original [RPhSiO 1.5 ] 8 macromonomers. Of particular importance is the fact that removing one corner from the cage also has little effect on the photophysics, indeed significantly improving fluorescence emission quantum efficiencies. However, removing most of the conjugated groups on the corner missing cage (from 7 to 2), e.g., [MeStilSiO 1.5 ] 2 [PhSiO 1.5 ] 5 (O 0.5 SiMe 3 ) 3 , eliminates the red-shift, implying the absence of a LUMO inside the cage. This suggests a minimum number of groups are needed to form such a LUMO. Also, for the first time, the radiation patterns for nonlinear, optically induced magnetic scattering at elevated light intensities are reported for these compounds and shown to support the same conclusiona spherical LUMO exists inside the cage.

A number of groups have invested considerable time synthesizing double-decker silsesquioxane (DD SQ) copolymers; however, to our knowledge, no one has sought to explore through-chain electronic communication between DD SQs via “conjugated” co-monomers. We recently demonstrated that stilbene derivatives of simple DD cages exhibit properties commensurate with formation of cage centered lowest unoccupied molecular orbitals (LUMOs), equivalent to LUMOs found in complete/incomplete SQ cages, [RStilbeneSiO1.5]8,10,12, [RStilbeneSiO1.5]7[O1.5SiMe/nPr], [RStilbeneSiO1.5]7[O0.5SiMe3]3, [RStilbeneSiO1.5]8[O0.5‑SiMe3]4, and [RStilbeneSiO1.5]8[OSiMe2]2. Such LUMOs support the existence of 3D excited-state conjugation in these cages. We describe here Heck catalyzed copolymerization of vinyl­(Me)­SiO­(PhSiO1.5)8OSi­(Me)­vinyl (vinylDDvinyl) with X–Ar–X, where X = Br or I and X–Ar–X = 1,4-dihalobenzene, 4,4′-dibromo-1,1′-biphenyl, 4,4″-dibromo-p-terphenyl, 4,4′-dibromo-trans-stilbene, 2,5-dibromothiophene, 5,5′-dibromo-2,2′-bithiophene, 2,5-dibromothieno­[3,2-b]­thiophene, and 2,7-dibromo-9,9-dimethylfluorene. Coincidentally model analogs were synthesized from vinylMeSi­(OMe)2. All compounds were characterized in detail by gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization-time-of-flight, thermogravimetric analysis, nuclear magnetic resonance, Fourier transfer infrared spectroscopy, ultraviolet–visible spectroscopy, photoluminescence spectrometry, and two-photon absorption (2PA) spectroscopy. Modeling of HOMO–LUMO energy levels of related compounds with R = Me rather than Ph was also explored. In the current systems, we again see apparent conjugation in excited states, as previously observed, as indicated by 50–120 nm red shifts in emission from the corresponding model silane compounds. These results suggest unexpected semiconducting behavior via vinylMeSi­(O−)2 (siloxane) bridges between DD cages in polymers. The thiophene, bithiophene, and thienothiophene copolymers display integer charge transfer behavior on doping with 10 mol % F4TCNQ supporting excited-state conjugation; suggesting potential as p-type, doped organic/inorganic semiconductors.

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well-defined structures and physical and mechanical properties. As part of this general exploration, we report unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si-(O 0.5 ) 2 ][PhSiO 1.5 ] 8 [(O 0.5 ) 2 Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red-shifts relative to model compounds, implying unconventional conjugation, despite vinyl(Me)Si(O-) 2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation, we explored Heck catalyzed co-polymerization of vinyl-ladder(LL)-vinyl compounds, vinyl(Me/Ph)Si(O 0.5 ) 2 -[PhSiO 1.5 ] 4 (O 0.5 ) 2 Si(Me/Ph)vinyl, with Br-Ar-Br. Most surprising, the resulting oligomers show 30-60 nm emission redshifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage. Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL-co-thiophene, bithiophene, and thienothiophene with 10 mol % F 4 TCNQ, suggesting potential as p-type doped organic/inorganic semiconductors.

A coordination complex, lithium hepta­(i-butyl)­silsesquioxane trisilanolate (1; Li-T7), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be highly soluble in nonpolar solvents such as hexane. The structure of Li-T7 was confirmed by NMR, IR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and computational simulation, providing detailed elucidation of the intermolecular self-association of the SQ cage with a box-shaped Li6O6 polyhedron through strong coordination bonds. After acid treatment, Li-T7 undergoes lithium–proton cationic exchange, yielding hepta­(i-butyl)­silsesquioxane trisilanol (2; H-T7) quantitatively. The high yield of H-T7 seems to be influenced by Li–O bonding in the Li-T7 complex that affects the selective formation of hepta­(i-butyl)­silsesquioxane trisilanolate and the bulky i-butyl groups which may prevent decomposition or SQ cage-rearrangement even at reflux under alkaline conditions. Single-crystal X-ray crystallography confirms the presence of the dumbbell-shaped SQ partial cages through strong intermolecular hydrogen bonds. Interestingly, lowering the polarity of the reaction solution by adding dichloromethane results in formation of the cubic octa­(i-butyl)­silsesquioxane (3; T8) cage in a good yield (47%), which is isolated by crystallization from the reaction solution.

This work presents a simple hydrothermal synthesis of nitrogen-doped carbon dots (N-CDs), fabrication of microfluidic paper-based analytical device (μPAD), and their joint application for colorimetric determination of total cholesterol (TC) in human blood. The N-CDs were characterized by various techniques including transmission electron microscopy (TEM), Xray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD), and the optical and electronic properties of computational models were studied using the time-dependent density functional theory (TD-DFT). The characterization results confirmed the successful doping of nitrogen on the surface of carbon dots. The N-CDs exhibited high affinity toward 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt (ABTS) with the Michaelis−Menten constant (K M ) of 0.018 mM in a test for their peroxidase-like activity. Particularly, since hydrogen peroxide (H 2 O 2 ) is the oxidative product of cholesterol in the presence of cholesterol oxidase, a sensitive and selective method of cholesterol detection was developed. Overall, the obtained results from TD-DFT confirm the strong adsorption of H 2 O 2 on the graphitic N positions of the N-CDs. The laminated three-dimensional (3D)-μPAD featuring a 6 mm circular detection zone was fabricated using a simple wax screen printing technique. Classification of TC according to the clinically relevant criteria (healthy, <5.2 mM; borderline, 5.2−6.2 mM; and high risk, >6.2 mM) could be determined by the naked eye within 10 min by simple comparison using a color chart. Overall, the proposed colorimetric device serves as a low-cost, rapid, simple, sensitive, and selective alternative for TC detection in whole blood samples that is friendly to unskilled end users.