from single photon producing nitrogenvacancy (NV) color centers consisting of a substitutional nitrogen atom next to a vacancy that is engineered artificially in the diamond lattice. The nanoscale effects related to artificially engineered NV color centers attracted important attention to diamond due to applications ranging from quantum computing to cell imaging. [2][3][4] The luminescence from NV centers is extremely stable without any photobleaching or photoblinking [5][6][7] and compared to better known quantum dots, ND brings additional advantages such as high biocompatibility [8,9] and simple C-surface chemistry. [10,11] This allows grafting of biomolecules that are interesting for cellular targeting [12,13] or biomolecular drug delivery. [14][15][16] However, for very small ND particles (5 nm) blinking of NV centers was observed, [17] showing that the surface effects are of importance for stabilization of NV luminescence properties.Here we describe how the surface chemistry effects can make the ND bulk luminescence sensitive to chemical processes ongoing at the ND surface, with the aim of using ND for monitoring a chemical environment such as surface charges or pH, cellular DNA/RNA hybridization, interaction with cell receptors, etc. The proposed method is based on the control of an electronic chemical potential at the

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SummaryThe biological tolerance of poly(N-substituted acrylamides) implanted subcutaneously to rats and pigs was investigated. Besides a macro-and microscopical evaluation of the implant and its surroundings, the surface changes of the implants were determined by means of a Stereoscan electron-optical microscope; the results obtained confirmed the very good in vivo stability of the polymers used.The histological analysis showed that all the polymers under investigation are very well tolerated by the organism and do not provoke any unfavorable reaction. The implants become surrounded with a granulation tissue which is gradually replaced by fibrocytes and collagen fibers situated in the basic substance staining positively with the alcian blue and PAS. In contrast with some authors we did not find a thicker capsule surrounding the implant on the sharp edges but on the flat planes. No calcification could be observed within the intervals investigated. The surface changes, which were studied electronoptically, were insignificant and connected with the way in which the implant was treated. No indications of malignant growth were observed.

The present paper deals with the transport properties of membranes made of hydrophilic gels containing ionogenic groups. Introduction of ionogenic groups into a gel based on 2‐hydroxyethyl methacrylate will affect the permeability of the investigated membranes for sodium chloride by an order or more. Dependences of the permeability on the content of ionogenic groups, three‐dimensional network density, and pH were established. The permeability for NaCl was compared for that for bivalent salt (MgSO4). It is shown, on the basis of independently determined distribution coefficients, that an increase in the permeability of ampholytic membranes in comparison with the neutral ones is primarily due to an increase in the diffusivity of the salt in the membranes with modified structure. It can also be concluded that an approximation of the free volume from the volume of the solvent in the membrane cannot be applied to the poly(2‐hydroxyethyl methacrylate) gel.

The diffusion coefficients of small paramagnetic tracers (nitroxide spin probes) and spinlabeled poly(ethylene oxide) in hydrogels were measured at 300 K, using two-dimensional spatial-spectral ESR imaging (ESRI). The gels were prepared by copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(2-hydroxyethoxy)ethyl methacrylate (DEGMA), in the presence of a fixed molar concentration of glycol dimethacrylate as the cross-linker and 4,4'-azobis(4-cyanopentanoic acid) as the initiator. Variation of the amount of water in equilibrium with the gel was achieved by polymerizing different molar ratios of the monomers.Experimental concentration profiles of the diffusant were measured as a function of time, and each profile was obtained by image reconstruction, from a complete set of projections. The diffusion coefficients were determined by simulating all experimental profiles, using the Fick model of diffusion for an initially confined tracer diffusing into a finite system. The diffusion coefficients depend on the amount of water in the gels. The variation of the diffusion coefficients D with the weight fraction of the copolymer in the gel is consistent with the free volume model. The variation of D with the molecular mass M of the diffusant scales as M~°'s in gels containing >67 wt % water and as M~1A for the gel containing 55 wt % water. The advantages and present limitations of 2D spatial-spectral ESRI for measuring transport properties in polymers are discussed.

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