In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

We show that meso-to-meso ethyne-bridged (porphinato)zinc(II) oligomers (PZnn structures) define exceptional low band gap organic materials that possess both large magnitude NIR S1 --> S0 fluorescence quantum yields and substantial S1 --> Sn absorptive cross-sections, tunable over a wide 850-1400 nm spectral window. These PZnn species possess fluorescence quantum yields (phif values) comparable to the highest reported for NIR laser dyes in the 750-900 nm regime; importantly, these emitters do not suffer from commonly cited tricarbocyanine dye drawbacks of poor photostability and substantial phif sensitivity to solvent polarity. Furthermore, tauo (kr-1) values determined using the Strickler-Berg method highlight the close correlation of fluorescence quantum yields with S0 --> S1 integrated oscillator strength and demonstrate a rare if not unique example of broad NIR spectral domain fluorescence energy modulation, where phif magnitudes follow a simple Strickler-Berg relationship.

Transient dynamical studies of ruthenium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2';6',2' '-terpyridine)2+ bis-hexafluorophosphate (Ru-PZn), osmium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2';6',2' '-terpyridine)2+ bis-hexafluorophosphate (Os-PZn), ruthenium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-15-(4'-nitrophenyl)ethynyl-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2';6',2' '-terpyridine)2+ bis-hexafluorophosphate (Ru-PZn-A), osmium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-15-(4'-nitrophenyl)ethynyl-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-(2,2';6',2' '-terpyridine)2+ bis-hexafluorophosphate (Os-PZn-A), and ruthenium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-ruthenium(II)-15-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-bis(2,2';6',2' '-terpyridine)4+ tetrakis-hexafluorophosphate (Ru-PZn-Ru), and ruthenium(II) [5-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-osmium(II)-15-(4'-ethynyl-(2,2';6',2' '-terpyridinyl))-10,20-bis(2',6'-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II)-bis(2,2';6',2' '-terpyridine) tetrakis-hexafluorophosphate (Ru-PZn-Os) show that these highly conjugated supermolecular chromophores feature electronically excited states that absorb over broad NIR spectral windows with considerable oscillator strength and manifest lifetimes (1-50 mus) that are extraordinarily long relative to those of classic low band-gap organic materials. The excited-state absorptive domains of these strongly coupled multipigment ensembles can be extensively modulated. For sequential one-photon absorptive processes, these compounds evince large sigmae, sigmae/sigmag, and sigmae - sigmag values. As the combination of all these properties within single chromophoric entities have heretofore lacked precedent within the NIR, these and closely related structures may find particular utility in a variety of technologically important optical-limiting applications.

A new series of chromophores, MPZn(n), which combine ethyne-bridged bis(terpyridyl)metal(II)-(porphinato)zinc(II) (MPZ(n)) and oligomeric, ethyne-bridged (porphinato)zinc(II) (PZn(n)) architectures, have been synthesized and characterized, along with a series of derivatives bearing pyrrolidinyl electron-releasing groups on the ancillary terpyridine units (Pyr(m)MPZn(n)). Cyclic voltammetric studies, as well as NMR, electronic absorption, fluorescence, and femtosecond pump-probe transient absorption spectroscopies, have been employed to study the ground- and excited-state properties of these unusual chromophores. All of these species possess intensely absorbing excited states having large spectral bandwidth that penetrate deep in the near-infrared (NIR) energy regime. Electronic structural variation of the molecular framework shows that the excited-state absorption maximum can be extensively modulated [lambdamax(T(1) --> T(n))] (880 nm < lambdamax < 1126 nm), while concomitantly maintaining impressively large T(1) --> T(n) absorption manifold spectral bandwidth (full width at half-maximum, fwhm, approximately 2000-2500 cm(-1)). Furthermore, these studies enable correlation of supermolecular electronic structure with the magnitude of the excited-state lifetime (tau(es)) and demonstrate that this parameter can be modulated over 4 orders of magnitude ( approximately 1 ns < tau(es) < 45 micros). Terpyridyl pyrrolidinyl substituents can be utilized to destabilize terpyridyl ligand pi(*) energy levels and diminish the E1/2 (M3+/2+) value of the bis(terpyridyl)metal(II) center: such perturbations determine the relative energies of the PZn(n)-derived 1pi-pi(*) and bis(terpyridyl)metal(II) charge-transfer states and establish whether the T(1)-state wave functions of MPZn(n) and PyrmMPZn(n) species manifest the extensive electronic delocalization and charge-separated (CS) features characteristic of long-lived triplet states that absorb strongly in the NIR.