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Photoactive reaction centers (RCs) are protein complexes in bacteria able to convert sunlight into other forms of energy with a high quantum yield. The photostimulation of immobilized RCs on inorganic electrodes result in the generation of photocurrent that is of interest for biosolar cell applications. This paper reports on the use of novel electrodes based on functional conductive nanocrystalline diamond onto which bacterial RCs are immobilized. A three-dimensional conductive polymer scaffold grafted to the diamond electrodes enables efficient entrapment of photoreactive proteins. The electron transfer in these functional diamond electrodes is optimized through the use of a ferrocene-based electron mediator, which provides significant advantages such as a rapid electron transfer as well as high generated photocurrent. A detailed discussion of the generated photocurrent as a function of time, bias voltage, and mediators in solution unveils the mechanisms limiting the electron transfer in these functional electrodes. This work featuring diamond-based electrodes in biophotovoltaics offers general guidelines that can serve to improve the performance of similar devices based on different materials and geometries.

A "patterned-seeding technique" in combination with a "nanodiamond masked reactive ion etching process" is demonstrated for fabricating vertically aligned diamondgraphite hybrid (DGH) nanorod arrays. The DGH nanorod arrays possess superior field electron emission (FEE) behavior with a low turn-on field, long lifetime stability, and large field enhancement factor. Such an enhanced FEE is attributed to the nanocomposite nature of theDGH nanorods, which contain sp2-graphitic phases in the boundaries of nano-sized diamond grains. The simplicity in the nanorod fabrication process renders the DGH nanorods of greater potential for the applications as cathodes in field emission displays and microplasma display devices. [ABSTRACT FROM AUTHOR]

Surface conductivity in hydrogen-terminated single crystal diamond is an intriguing phenomenon for fundamental reasons as well as for application driven research. Surface conductivity is also observed in hydrogen-terminated nanocrystalline diamond although the electronic transport mecha-nisms remain unclear. In this work, the piezoresistive properties of intrinsic surface conductive nanocrystalline diamond are investigated. A gauge factor of 35 is calculated from bulging a dia-mond membrane of 350 nm thick, with a diameter of 656 µm and a sheet resistance of 1.45 MΩ/sq. The large piezoresistive effect is reasoned to originate directly from strain-induced changes in the resistivity of the grain boundaries. Additionally, we ascribe a small time-dependent fraction of the piezoresistive effect to charge trapping of charge carriers at grain boundaries. In conclusion, time-dependent piezoresistive effect measurements act as a tool for deeper understanding the com-plex electronic transport mechanisms induced by grain boundaries in a polycrystalline material or nanocomposite. [ABSTRACT FROM AUTHOR]

A detailed conductive atomic force microscopic investigation is carried out to directly image the electron emission behavior for nitrogen-doped diamond nanorods (N-DNRs). Localized emission measurements illustrate uniform distribution of high-density electron emission sites from N-DNRs. Emission sites coupled to nanographitic phases at the grain boundaries facilitate electron transport and thereby enhance field electron emission from N-DNRs, resulting in a device operation at low turn-on fields of 6.23 V/μm, a high current density of 1.94 mA/cm 2 (at an applied field of 11.8 V/μm) and a large field enhancement factor of 3320 with a long life-time stability of 980 min. Moreover, using N-DNRs as cathodes, a microplasma device that can ignite a plasma at a low threshold field of 390 V/mm achieving a high plasma illumination current density of 3.95 mA/cm 2 at an applied voltage of 550 V and a plasma life-time stability for a duration of 433 min was demonstrated. [ABSTRACT FROM AUTHOR]

This work presents a morphological and structural analysis of CVD diamond growth on silicon from nanodiamond seeds covered by a 50 nm thick chromium layer. The role of carbon diffusion as well as chromium and carbon silicide formation is analyzed. The local diamond environment is investigated by scanning transmission electron microscopy in combination with electron energy-loss spectroscopy. The evolution of the diamond phase composition (sp 3 /sp 2 ) is evaluated by micro-Raman spectroscopy. Raman and X-ray diffraction analysis are used to identify the interfacial phases formed during CVD growth. Based upon the observed morphological and structural evolution, a diamond growth model from nanodiamond seeds buried beneath a thin Cr layer is proposed. [ABSTRACT FROM AUTHOR]

Surface pretreatment by gas discharge plasmas of N 2 , O 2 and CF 4 is studied for enhanced diamond nucleation on Cr surfaces. The seeding density following the interaction of water-dispersed nanodiamonds (NDs) and the Cr surface is enhanced due to chemical modification of a surface. The surface that is untreated or pretreated with N 2 plasma possesses a suppressed electrostatic attraction of NDs, while the pretreatment with O 2 or CF 4 plasmas render a strong electrostatic attraction and high seeding density. Finally, by this method thin nanocrystalline diamond films are achieved on Cr surfaces after O 2 and CF 4 plasma pretreatments. [ABSTRACT FROM AUTHOR]

Abstract: The high prevalence of cardiovascular diseases (CVD) demands a reliable and sensitive risk assessment technique. In order to develop a fast and label-free immunosensor for C-reactive protein (CRP), a risk factor for this condition, anti-CRP antibodies were physically adsorbed to the hydrogen (H)-terminated surface of nanocrystalline diamond (NCD). An Enzyme-Linked ImmunoSorbent Assay (ELISA) reference technique showed that this was a suitable substrate for antibody–antigen recognition reactions. Electrochemical Impedance Spectroscopy (EIS) was used to electronically detect CRP recognition. The specificity of the immunosensor was demonstrated by incubation with CRP and plasminogen as reference molecule. A different impedance behavior was observed in real-time after CRP addition as compared to plasminogen addition: the impedance increased only during CRP incubation. Fitting the data showed that this corresponded with a decrease in capacitance of the molecular layer due to its increased thickness by specific CRP recognition. Sensitivity experiments in real-time showed a clear discrimination between 1μM, 100nM, and 10nM of CRP after 10min at 100Hz. Since, 10nM of CRP was still clearly distinguishable from buffer solution, our CRP-directed immunosensor prototype reaches a sensitivity that is within the physiologically relevant concentration range of this biomarker in healthy controls and CVD patients. Moreover, this prototype displayed real-time discriminating power between spiked and unspiked serum, and thus also shows its applicability in this biological matrix. [Copyright &y& Elsevier]

Abstract: We propose a new method of detecting the functional groups at the NCD surface based on the interfrence-free infrared reflection absorption spectroscopy of p-polarized IR light at Brewster''s angle of incidence (BA-IRRAS). We report IR absorbance spectra of a linker molecule monolayer (10-undecenoic acid) covalently bonded to the NCD surface with and without DNA fragments coupled to it, and IR spectra of organosilane polymer coatings deposited on NCD surface by the spin coating technology. The homogeneity of the surface coatings was monitored by fluorescence microscopy. [Copyright &y& Elsevier]

Atomic defect centers in diamond have been widely exploited in numerous quantum applications like quantum information, sensing, quantum photonics and so on. In this context, there is always a requirement to improve and optimize the preparation procedure to generate the defect centers in controlled fashion, and to explore new defect centers which can have the potential to overcome the current technological challenges. Through this work we report enhancing the concentration of Ge and Xe vacancy centers in microcrystalline diamond (MCD) by means of He+ irradiation. We have demonstrated controlled growth of MCD by chemical vapor deposition (CVD) and implantation of Ge and Xe ions into the CVD-grown samples. MCDs were irradiated with He+ ions and characterized through optical spectroscopy measurements. Recorded photoluminescence results revealed a clear signature of enhancement of the Xe-related and Ge vacancies in MCDs. [Display omitted] • Ge and Xe ions were implanted in microcrystalline diamond (MCD) films grown on Si substrate. • MCDs were irradiated with He+ ions and annealed. • Photoluminescence signal increased for Xe and Ge vacancy centers. [ABSTRACT FROM AUTHOR]

• Electrostatic double-layer dominates in Ta surface-nanodiamond particle interaction. • Explaining the surface contamination impact on particle–surface interaction. • High nanodiamond nucleation achieved on hydrophilic and hydrophobic Ta surfaces. The surface of tantalum (Ta) thin films is exposed to different gas discharge plasmas (N 2 , O 2 , CF 4) followed by an investigation of surface wetting properties and water-based colloidal seeding of ultra-dispersed nanodiamond (ND) particles. Fluorination of the Ta surface resulted in a hydrophobic surface, whereas other surface treatments resulted in hydrophilic surfaces. Regardless of treatment and wetting contact angle, the ND seeding density of approximately 2 × 1011cm−2 is obtained for all the samples. This shows that the electrostatic interaction of the Ta surface with ND particles is the primary factor determining the successful ND seeding, while the surface wetting property is of lesser importance. In addition, Ta surface contamination dynamics and its impact on ND seeding is studied. An analytic model is proposed to account for surface contamination and explain its impact on the ND seeding density. The model can be more generally applied for other material systems. [ABSTRACT FROM AUTHOR]